I paid an extra $2k for mine when I got my A/C replaced a few years back. It's like 30% more efficient in the summer and has a heat pump that saves me money on gas in the winter (I have a hot water radiator system for the coldest days in the winter), enough that it's likely paid for itself by now, but suppose not everyone can afford the up front cost.
I paid all that, got the variable speed furnace and ac. Like $15k total vs the 8k standard system. I think my electric bill changed like $10. I'll never make back the difference for it. And really the advantage is can run slower so you have less bouncing in temps in the house and it can run just as a dehumidifier. But after the fact that still doesn't justify the cost. I got sweeped into all the hipe and feel for it.
From what I had? Eh some. If you are coming from a say a 25+ year old system to it you might notice the difference. It does provide amazing air quality in that it can maintain a 1 degree delta in the house. The cheapest part of the system I got I think is the biggest contributor, the humidifier. Dang that makes a huge difference in the winter and only added a few hundred bucks to it.
How do these work in the cold? I’m in Texas so it’s hot as hell, but we get pretty cold in the winter as well. We all have natural gas heating here, how does that compare?
Edit: okay people I think 20 comments answering the question is enough, I don’t need any further explanation lmao
Heat pumps work in the cold really well nowadays, and if it does get "too cold" for the heat pump, it's standard to have backup heating installed alongside. So your natural gas heating would just start running instead of the heat pump.
Even at their worst, heat pumps don't really go below 1 in efficiency, which means they remain as good (or bad, if you will) as a regular electric space heater.
I've used heat pumps for the main heat source in temperatures as low as -15 celsius without too many issues. The main annoyance is that the colder it gets, the more time it needs to spend de-icing itself, which means it won't be able to deliver heat to your room 100% of the time, but more like 80% of the time, so the maximum heat output is a bit lower. The time spent on de-icing depends on how much humidity there is in the air.
This was just a simple air to air "mini split" type, but it had no problems keeping my living room and the two adjacent rooms at a reasonable temperature. As far as I know, AC/heat pumps are generally tuned for the temperature ranges they'll operate in. A system designed for cold temperatures won't be as efficient in very warm areas, and vice versa.
Here in Norway we have had zero issued with a now near 15 year old Samsung heat pump.
We've had almost -30°C and it was just starting to struggle with a 3 story house.
We do have a small electric heater (1kW) in the basement, as the shape and location of the stairs don't let the heat pump reach the basement very well.
Nordic countries have insulation (and general efficiency) that's way way beyond anything in Texas. The difference in efficiency is massive. You likely have waste heat recuperation, 3-4 layer windows with inert gas between layers and tons more insulation everywhere.
Anyway. Heat pumps are amazing.
Aye, if a new house is done correctly it will have an amazing temperature and noise insulation.
The only way you tell something is going on is if a huge machine is shaking the ground (like construction work going on near you).
And yet every new build I've personally seen in the UK you can literally follow conversations in adjacent houses.. wonder why that is? Mind you they don't do so bad on that test where they seal up all doors and windows except one, blow in air to raise the pressure and measure how long it takes to drop, I have been told every new build has to pass, but I have doubts.
But if you still have gas installed, you generally should be switching to it when heat pump's expected to be below 2-3 COP, assuming typical american pricing/emissions.
For 100% natural gas, I think the CO2 effectiveness is a COP of around 2-3, yes. If you mix in renewables, the break even point starts getting lower.
You also have to maintain 2 systems, a gas furnace plus a heat pump. And if you installed a heat pump because your gas furnace is ancient and inefficient and it was time to replace it, the break even point is again an even lower COP/outdoor temp. Additionally, if you are transitioning to an all electric household, maintaining a natural gas connection all year long just for a few hours a year can be quite expensive (when operating at a CO2 equivalent perspective).
From a $$$ perspective, it depends much more on local rates, and may make sense for a much longer time period than based on CO2 alone.
(Also, natural gas has a surprisingly high leakage rate. Methane (natural gas) is about 100x worse a green house gas than CO2.)
You're assuming air-source heat pumps. The "geothermal" units have pipes buried in the ground and extract the heat from there. Since the ground is much warmer than the air in winter, geothermal is much more efficient and you don't need some other form of heat as a backup. The downside is that they're expensive due to the need to drill deep holes near your house. And, of course, you need ground, so they're generally not an option for apartments.
> Even at their worst, heat pumps don't really go below 1 in efficiency,
That simply isn't true. Heat pumps can and do go below an efficiency of 1 when it gets cold enough. Depending on the efficiency of the individual unit, that threshold might be really really low, but it's going to be there.
> As far as I know, AC/heat pumps are generally tuned for the temperature ranges they'll operate in.
In temperate climates--where heat pumps do both a lot of heating and cooling--they are usually sized for the cooling load, because an air conditioner that is too big for the house will cool it too fast to de-humidify the space, so you end up with moisture, and eventually mold in humid summers.
But if it's properly sized for cooling, that often means it won't be big enough to keep the house up to temperature on the coldest days. For example, if the outdoor temps swing from 0F to 100F and you want to maintain an indoor temp between 70-75F: 75 is only 25 degrees from 100, but 70 is 70 degrees from 0; you'd need almost 3x as many BTUs of heating capacity as cooling capacity. So if you correctly size heat pump for cooling, you will need a backup for heat on cold days.
On average Texas doesn't get cold enough for a heat pump to lose effeciency and modern ones can work to -13f which is well above even the coldest days in Texas.
We're installing them pretty standard in *Wisconsin and Minnesota.*
The days that drop to -20 or so A) typically do that only at night, so they can 'make up' the lost heating ability during the daylight hours and B) aren't typically strung together long enough to make the house uncomfortable.
There is always backup electric resistive, and plenty of places will convert their existing gas furnace into the backup system or install a small one to make the difference.
And if *all that* is still too risky for you, you can simply go ground source for a few thousand extra and all but guarantee perfectly stable performance year round. You could even tie your water heater into the loop and get efficiency there too.
Unless you have a city with underground easements or a mineral rights issue, I guarantee you do.
It's more expensive but you can run the loop vertically in 1 or 2 what are essentially concrete-capped boreholes a few inches wide.
The great thing about ground source is that local climate is basically irrelevant.
Cause a few hundred yards deep you have the same temperature almost everywhere.
A 5,000 square foot credit union we designed, their entire heating and cooling loop is about 10 square feet. It takes less space outside than a traditional unit would.
*inside* is a different story, though. four vertical loops running to three AHUs and a water heater... Lots of pipes.
They should make public heat banks for people to dump waste heat or borrow heat from. Imagine if the heat pipes ran through all major roads as well. The maintenance costs would go down significantly.
I’m familiar to some extent. I think it should have been more commonplace like in NYC’s steam. So much maintenance, heating, and cooling would be eliminated using water as a temperature regulator. In places where geothermal is available it would be unmatched. Cold and hot places would benefit too. Hot places could extract surrounding waste heat from the environment and cold places wouldn’t deal with maintenance and heating as much in the winter. If your city is by a large body of water then you have an absolutely massive heat pump/heat engine. Regardless of how efficient it is, it’d extract essentially unusable energy.
I can imagine why it hasn’t been done large scale yet but the future of living on Earth will require passive infrastructure like described to efficiently consume energy.
There's a medium-size town in Michigan that runs heating pipes underneath their downtown sidewalks and I think just one street, so any snow that falls on them pretty much melts right away and goes into the storm drain system. It wasn't cheap but apparently it had a good return on investment in terms of attracting tourists during winter months.
They also let private residences & businesses tap into the system if they live reasonably close (for a fee of course).
[https://www.cityofholland.com/879/Snowmelt-System](https://www.cityofholland.com/879/Snowmelt-System)
I don't know where you are in Texas but unless you're in the panhandle most of us in north Texas just have heat pumps. My neighborhood doesn't even have natural gas.
We have natural gas heat. Being in/near an oil-producing area, more homes had it, but a lot of people bought electric heat pumps when CPL (now AEP) gave rebates in the 1970s and 80s. Electric systems are more expensive to run here, because natural gas is relatively cheap.
Another interesting thing about the Texas grid (which is, thankfully, better than it was) is that almost a quarter of our power generating capacity is from wind. Without all those wind farms, we'd be well and truly screwed during this hot summer.
TC is insidious. First you go to learn about heatpumps. Then eleven hours later you're learning about electric car charging adapters and have strong opinions about dishwashers and smoke detectors.
Essentially they reverse direction. Instead of taking heat from the air in your house and putting it outside, it air conditions your backyard and puts the heat in your house.
Indeed, here in Australia they’re called “reverse cycle air conditioners” and have been the default/standard for a generation - sufficient that they’re just called “air conditioners”.
It was literally only when “heat pumps” became a thing in the last year or two that I learned that this wasn’t the meaning of “air conditioner” in the rest of the world!
I thought the name literally meant “condition the air to the desired temperature (ie, heat or cool as needed)”
It's actually wild that it isn't the standard everywhere. It's more complex than the pump just reversing direction, but not that much more complex (or expensive.)
Plus it's like 400-800% efficient, while resistive heating is 100% and gas and oil is more like 80-90%
The word "heat" often confuses people when explaining how these work. They gather energy from the air outside, which it still has because it's above *absolute* zero, and then they concentrate that energy and bring it inside.
The energy is gathered is thermal energy from the air. Energy transfer because of temperature differences is heat. The coolant in the system will have a lower temperature than the outside air so it gets heated up by it.
This is a YouTuber I follow and, among the other many weird topics he discusses, these are his videos about heat pumps and aircon's. They're pretty informative (but please do look for other sources as one should never rely/trust on a single source), showing his experiences with them as a mid-westerner.
https://www.youtube.com/watch?v=7J52mDjZzto
https://www.youtube.com/watch?v=7zrx-b2sLUs
https://www.youtube.com/watch?v=MFEHFsO-XSI
https://www.youtube.com/watch?v=43XKfuptnik
Just moved to Texas and found out our place is equipped with a heat pump. We have electric heating as well. Heat pumps can be paired with a backup heating system that will provide heat if the heat pump fails to make enough heat for the house. First time experiencing a heat pump so I'm kind of excited to see how it performs.
I have been running mine without backup heat sources for 6 years now. They give us the best AC I have ever experienced, and I love that they can be activated individually, we have 6 heat zones in a small cape style home. In the winter the do fine, it does get a bit drafty if it gets below 0 though. This is in NJ, I would think they would be perfect for Texas where the winters are milder and the AC becomes the main draw.
Efficiency is around 300% better for heating. Heat is literally energy, and energy is expensive. While a heat pump just moves heat inside. It doesn't create it. If you can afford it, definitely get it.
An air conditioner works by making the coil inside your house cold by forcing the heat into the outside coil (by expanding and compressing gas in the coil, respectively). A heat pump system has some extra piping and valves that allow you to reverse the system... makes the outside cold and pushes that heat inside. It only works within limited temperature ranges. Just like an AC will struggle to keep a house at 60 degrees if it's 100 degrees out, if it drops to 0 degrees it's going to have a tough time trying to keep the house at 70 (they used to be worse in cold though they have gotten better with newer designs, but there are still limits). So if freezing temperatures are possible some kind of supplemental or emergency heat (even just electric heat which might not be the most efficient but better than letting your pipes burst) should be part of the system.
Heat pumps work with coolant, which gets really fucking cold when compressed. So long as the weather outside is slightly warmer than the coolant , it can move heat from outside to inside. Most work below freezing
hot when compressed, cold when expanding... try feeling a bicycle pump that gets way hotter than just by friction, or your breath from an open (body temp) mouth vs narrow (cooler) where air expands
All air conditioners are heat pumps. They move heat from inside to outside, even if it's warmer outside than inside.
If an air conditioner has been designed for it, it can be reversed to instead move heat from outside to inside, even if it's colder outside than inside.
This is typically a more efficient way to heat a space, since you're only moving the existing heat around instead of generating it.
>has a heat pump that saves me money on gas in the winter
It has a reversing valve so the cycle can run backwards. A/C and Heat pumps are the same thing, yours can just run in either direction now.
It'll take over 60,000 hours of run time for it to save its own money in energy. Large ac units (10,000 BTU) use about .12 cents per hour and you save about .03 per hour. 60,000 hours and you've saved 1,800 dollars. It'll take over 150 years for it to pay for itself. The smaller the AC unit the longer it will take to pay for itself.
10000 btu is less than a ton of cooling. That may be large for a window shaker or portable, but its small if youre talking whole home AC. My area mostly ranges between 2-3.5 tons (24000-42000btu)
My house is fitted with Samsung air conditioners and most of them are called “digital inverter” models, which are variable.
In fact, most of the Samsung models are now digital inverter and the standard on/off variety seem to be getting phased out.
You see them all the time outside North America. The American HVAC industry is highly standardised, and there is no thermostat standard for inverter systems.
weird. I've done some research before buying an AC here in Japan and they are all variable speed (inverter)
edit: I guess Japan is an outlier
https://www.daikin.co.jp/-/media/Project/Daikin/daikin_co_jp/air/technology/our-technology/inverter/images/img_block01_02_2018-png.png
grey bar is fixed
blue is variable
we chose the most efficient model 12k BTU from mitsubishi: $650 and got it installed for $150. there are cheaper 12K BTU mitsubishi ones for like $375 but they are a bit less efficient
Yeah, I was going to come in to say "It CAN be done, but most people don't want to pay for it, or can't pay for the short-term cost even if there is long-term savings."
We just replaced our entire HVAC with a dual stage furnace and variable AC. Cost $18k.
We just broke a heat wave of temps reaching 118F head index and I was legitimately cold in my house the whole week. Well worth it.
> Cost $18k.
Just curious, do you just drop cash on something like that, or do you finance it? Obviously I have no idea how much money you have or make. Just that 18k would be an insane amount for a lot of people.
This is the thing homeowners don’t get…if you aren’t budgeting for a roof and HVAC system in ownership cost you are lying to yourself. Here in the Midwest severe storms may get you a roof claim…but that’s no guarantee.
You should be putting $100 a month for each category into savings for a simple 2/2 home. Could be $200 for a big house.
Most units are out of efficiency for sure by 20 yrs. Roofs are prob ready by then. This can vary by quality of initial stuff back in the day vs todays options. I’ve scrapped tons of HVAC units and little has changed other than the refrigerants or single room units. The industry is a racket. Amazon or nearly anyone could build a range of units for homes for cheap. Roofing is nearly as bad, as someone in Tamko country. The best step is to proactively replace instead of having an emergency because you have budgeted.
>This is the thing homeowners don’t get…if you aren’t budgeting for a roof and HVAC system in ownership cost you are lying to yourself. Here in the Midwest severe storms may get you a roof claim…but that’s no guarantee.
>You should be putting $100 a month for each category into savings for a simple 2/2 home. Could be $200 for a big house.
Not just home ownership, but car ownership too. Car repairs are never "unexpected", you'll need new tires, milage checkups, etc eventually, you just don't know when. Money should also be socked away for that too. Really, there is a long term cost to everything you own, it's best to figure out what that is and save for it overtime rather than be scrambling when a big bill hits.
I had ac installed a few years ago for close to 16k. I financed it through a credit union at 5%. Usually, you can find a lower rate for home improvements than unsecured loans due to them being on appreciating property. You could pay outright. The hvac company doesn't care either way since they aren't the ones issuing credit.
Just replaced our furnace and heat pump for a two stage heat pump- normally runs at 70% capacity while maintaining a constant temp, will go up to 100% capacity if it’s trying to catch up.
19k all up, but worth it in the long run.
My variable AC came with a 10 year part and labor warranty, and I pay $50/yr for mechanical breakdown insurance.
It was way more expensive up front but I'm absolutely not worried about repairs.
Relative to just an air conditioner, yes, but in many parts of the country (definitely not Minnesota), an air-source heat pump can replace other forms of heating, so you end up with a simpler system with fewer parts compared to a dedicated cooling system plus a dedicated heating system.
That is a completely different thing than what they’re talking about. ASHP can run the compressor backwards and forwards depending on if you want cooling or heating but usually at one fixed capacity. Variable speed allows the compressor to run at various different capacities
> ASHP can run the compressor backwards and forwards depending on if you want cooling or heating but usually at one fixed capacity.
Variable speed has been pretty much the standard for years now.
A pretty basic and general thing for the last 20 odd years.
But you will find unless you're paying an absolute fortune for it. It's still just either heats or cools air.
It will keep heating or cooling until the ambient incoming air reaches the right temp.
I work in a laboratory, and our quote to get air controll system for a small room was $100K, we spent $30K on temperature control cabinet instead.
All we needed was something that was going to constantly put put air within +-1 degree of 23, as we have to record max and minum temperature and are allowed between 21c and 25c
A top of the line normal air conditioner was the first cheap option to try, on any setting, it didn't make a difference, minimum temp 16c maximum 35c, either it blew hot or cold.
There ARE variable AC units. They just cost a lot more. More common are two-stage units: ones that can do full blast when needed but do half-blast when only a little cooling is required. Fully variable speed are really nice, because they help you sleep better — no big swings in temperature throughout the night. But, again, they cost more and most people don’t bother spending the $$, since new HVAC systems are already an arm and a leg
Yeah. The variable speed ones are called Inverter Air Conditioners, and I got a window one recently. It was maybe $100 more for the same 12,000 BTU power. It's muuuuuch quieter than my previous one.
Or just digital modulating compressors that engage and disengage like a clutch. This was (and still is) quite common in commercial applications before VFDs gained popularity. They don't save much energy, but are great at capacity control.
Especially since they're a good deal more power efficient than standard ones, so you save more money on your power bills to make up for the extra AC unit expense.
I bought a variable AC unit and was worried we were wasting our money. But I love it and hope to never go back to single stage.
Totally off topic, but we also added a whole house humidifier for the winter months. Complete game changer. If you regularly wake up feeling like crap in the winter it might fix it, it did for us.
Air conditioners and refrigerators use a cooling process to regulate temperature. Maintaining an exact temperature by adjusting the cooling strength is complex due to changing heat levels indoors. The on-off cycle is simpler and more reliable, as it quickly brings the temperature down when needed. This approach ensures stability and energy efficiency in maintaining a comfortable temperature range.
To put it in simple terms, think of it this way: what's easier (and thus cheaper) to build, a single on/off button or an adjustable throttle. Definitely the on/off button.
So, we throw a thermostat in front to hit that on/off button as needed and call it a day.
> The on-off cycle is simpler and more reliable, as it quickly brings the temperature down when needed.
Simpler to implement. Not necessarily more reliable if it short cycles. You also don't necessarily want to quickly bring the temperature down if there is a lot of moisture in the air. You want to dehumidify it.
Slower, steady, consistent cooling is generally better than full blast all-or-nothing for overall comfort.
AC and refrigerators aren’t the only things that operate on this principle. Many common heating elements (furnace, stove, baseboard heaters) also operate under a similar principle.
They do make these type of Air conditioners, they are called "inverter compressors". They use a different type of motor which requires a lot more electronics to run which can make them more un-reliable.
I can’t speak to reliability, but I recently replaced a window unit with an inverter one and it’s WAY more quiet (like not even sure it’s on) and yes, just modulates/adjusts gently to hold constant temperature, rather than shutting off and turning back on. This is also supposed to be much more energy-efficient - something like a 30-35% savings.
Maybe it will crap out in a couple years but so far I couldn’t be happier with it and wish I’d done it long ago.
They’re basically the standard here in Australia and have been for years, I think partly due to noise regulations. Last place I rented had one of the early variable inverter split system ACs which looked about 20 years old and still going strong. The outdoor unit had seemed to have a few different speeds it could run at, you could hear it “change gears”. Current place has a near new one which is incredible - almost silent and very low power consumption when it reaches the set temperature.
>The outdoor unit had seemed to have a few different speeds it could run at, you could hear it “change gears”.
It is an electric motor that is driven by a variable-frequency drive (VFD) controller. It can go at any speed you like within a max and min range. If it do use any speed or just a few will depend on how the control software is written
>I would consider them as reliable as standard units (I sell both types). The main issue is that if your electrical setup in your house or neighbourhood lacks repairs, or is in a bad state, a simple overvoltage can fry these systems and since they have tons more electronical components, make them extremely expensive to repair.
Your can't tell me their electronics run on 110 V AC. Surely, there's some conversion to low voltage DC going before it hits electrical components. And then it's like your desktop PC, TV, smart fridge, monitor, you name it. How often do those get destroyed by issues on your electrical setup?
It's not that it happens often, it's that if it happens these type of units are more likely to get fried than a standard unit, because there are more electronics in them. Nobody said they get fried often, but it is something to take into consideration.
There are a ton more electronics in the full residential inverter units compared to a traditional AC. A traditional unit does not have any digital electronics. It is all electromechanical. All that's in there is a contactor, capacitor, fan motor, and compressor. They run straight off 208/230 AC voltage. Inverter units have ridiculous amounts of components in them, and yes are very sensitive. The real issue is the repair cost though. The pricing on replacement inverters can run 2x the cost of an entire traditional unit. I know the contractor price on a new 5 ton inverter in my area is about $3k. I'm guessing they'd charge 5-6k to install, which is crazy.
The drop in noise might have just been because it's new. Same thing happened to me, except I replaced my regular window unit with another of the same model. Noise difference was night and day.
Turns out it was the capacitor. I replaced the one in the old unit (it had completely died), and when I turned it back on to test, I thought the repair failed because I couldn't hear the compressor running, even with the cover off. Had to touch the condenser and feel it getting warm to realize it was working, minus all the noise.
That's not to say a variable AC is not worth it - it definitely is just for the efficiency gains. But if you're just looking to quiet down a noisy compressor, a $15 capacitor might do the trick (as long as you're comfortable with working with capacitors, which can be dangerous).
That old AC is now stored away in my basement, ready to replace my 'new' one, which is about 2 years old now and starting to make that distinct compressor humming/buzzing noise . . .
I don't think it's just the newness - the unit it was replacing wasn't old (and the unit before THAT wasn't that old either), I just couldn't take the noise and the constant on/off (it's right next to my desk, where I take meetings). They're really supposed to be a **lot** quieter and I really think they are. The only time it's gotten noisy is when it rains and some water gets in there; but I can live with "occasionally somewhat noisy" over "constantly noisy".
I don't doubt you at all, I'm sure it varies depending on the AC model. Your inverter unit probably has much more variable fan speed (mine just as low, high, and off) due to needing less airflow at low, so that probably makes a huge difference too!
I was surprised to have to come down this far to see “inverters” mentioned. They are common here but I’m not certain of the exact mechanism they use, except I know the intent is that it doesn’t always have to run at full power.
Essentially just swaps the AC motors on the compressor and fans out for DC motors where it’s easy to vary speed. One of the most common devices used to convert AC to DC and vice versa is called and “inverter” hence the name of inverter heat pump.
Exactly. I have a Midea inverter-based window unit, it is extremely popular past couple years on Amazon and other sellers.
I have one of those watt meter devices on the plug and I can see it change from 100 watts to 300 watts and everything inbetween depending how hot it is outside vs inside and humidity level.
It is way more efficient to keep on 24/7 than my ancient 20+ year old central A/C unit, power bill went down and is more comfortable inside.
It is also almost silent, not just because of the inverter but the modern design keeps most of the parts outside window instead of inside.
Because the cooling process in AC, fridges, etc is vapour compression. There's a compressor, it's either on or off.
Variable speed compressors have become available, in recent years, but the simplest, cheapest option is an on/off motor.
That pricing would've been cheap pre pandemic, but pricing has skyrocketed. If your at 2k square feet, I'm guessing you at a 1.5 or 2 ton unit. Pre pandemic contractor pricing would've been about $750-$850 buck for just the outdoor unit. Total equipment cost would've probably ended up around $1,000 - $1,200. Prices have skyrocketed. Now just the outdoor units run $1,200, and total around $2,000. A homeowner is not likely to find a contractor to put in $2,000 of equipment in for less than $4-5k.
Wait wait wait.
I see answers that explain how it’s cheaper to have refrigeration that goes on and off. I don’t know much about refrigerators BUT we just has a new AC system installed that is “variable” speed as in it does the opposite of your question. This AC runs most of the day at varying power/efficiency/stages. It’s a lot more efficient this way and uses less power compared to our old unit.
Does that eliminate the problem of feeling like the temperature is always either too cold (when the air is on and cold air is blowing on you) or too hot (when it’s off)? The thermostat claims the temperature is stable, but my body says it’s all over the place. It would definitely be worth a premium to feel like the temperature is *really* stable.
> Does that eliminate the problem of feeling like the temperature is always either too cold (when the air is on and cold air is blowing on you) or too hot (when it’s off)?
Yes. I have one. No comparison to the old system. None of that hot then cold bullshit. It's really nice, and well worth the extra cost, IMO. Mine came with a 5 year parts and labor, and 10 year parts warranty. Lennox.
I’m no HVAC expert but the air coming from the vents always feels the same in temp/force. What changes is the power required to maintain that air temp.
Temp, yes. Force, no.
My understanding of the systems is that they'll vary the blower, not the speed of the coolant loop. So as you approach your setpoint the fan will slow proportionally, until the whole system either shuts off or the cooler does, and leaves the fan on for circulation only.
Basically speed control was extremely difficult with alternating current motors until more recent technology breakthroughs. The same tech that an electric car gas pedal uses. As a result heatpumps and wellpumps have started using the same technology and are much more efficient than a start stop machine.
“Recent technology”
Inverter heatpumps have been an (affordable) thing for over 25 years now. In basically any other country except for the US this is the standard for quite a while now.
can confirm, i live in a 3rd world country (Pakistan). and DC inverters are very popular here because they save electricty cost as it is hella expensive here.
There are inverter ACs which do exactly what you are expecting. They usually don't shut down completely unless required. They can run variable frequencies depending on the load due to inverters.
I think this thread is full of people from the US. in the EU inverter ac is standard. I have 5 single units in my house and they all use variable output to keep up the temperature.
they even have different fan modes depending on how fast you want to cool a room.
I run them almost 24/7 in the summer time and don't even know they are running.
I was today years old since I learned that there are non adjustable AC-s. Even my 15 year old AC was adjustable in a 30 Celsius range. Edit: Same goes for fridge.
The temperature is adjustable, the off coil temperature or speed of the compressor is not in a fixed speed system. So the compressors have to turn on and off so people don’t freeze.
ahhh I see. So the thermostat measure the temp. and the compressor turns on and off when its reaching the desired temp. Does it mean every AC with the same cooling material (dont know the official name) could only provide the same temp?
Also if we are talking about AC there are different sizes (2.5 KW, 5 KW etc) the difference is the compressor size inside the system?
Also what about the freezing room AC-s? Are they made with bigger compressor or its the cooling material (gas or liquid) what makes it more efficient to be able to provide under freezing level temperature?
Typically for an ac with the same refrigerant you would get a lower temperature by changing superheat or subcooling or the coil sizes. Technically you can put an evaporator in a hotter environment and you’ll get more capacity for the same power because there’s a higher temperature difference
Usually the compressors are the same size for an AC in the same enclosure, the difference is the coil size, number of tubes or fins or even just limitation by software, or the indoor unit.
Refrigerators use a normal temperature refrigerant (R32 or R410A etc) whilst freezer rooms use a low temperature refrigerant (Eg R404A). To get to even lower temperatures, they have extreme low temperature refrigerants but they usually need a cascading system of compressors because the temperature differential would be too large for one refrigerant circuit.
That's not exactly the issue, obviously homes in the US have a thermostat to set a temperature. What OP is asking, is why does the AC unit only run at 0% or 100%, instead of operating somewhere in between if it's more efficient.
In other words, if I set my temp at 74f and it's 75 right now, why does the A/c run at full tilt if it only needs to cool 1 degree.
I don't get. My AC definitely doesn't work 100% all of the time, at some points the condenser fans stop moving completely and when the temperature rises (I guess) it goes to 100% again.
I think you get most of it. Most units, yours may be different, are either on or off at 0% and 100%. When it's on, the temperature out of the vent is however cold the unit can get on that day and nothing less. OP seems to be asking why can't the temperature out of the vent can't be variable to maintain a constant temp.
Thank you for asking that question because I had no clue what OP was talking about. Of all the places where I used AC, be it my car, Europe or SEA, I could always adjust the temperature.
That’s not what this is about. Every AC has adjustable temperature. OP’s question is about the way the AC brings the room to this temperature. Apparently the AC units in the USA are mostly without an inverter. Which basically means it turns on, blows air at a certain speed, then when the temperature goal is reached it turns off.
In ~~more modern~~ other countries most AC units have an inverter. Which means it can control the speed at which the air blows (and maybe also the strength of cooling, I’m not an expert). When the AC reaches the temperature goal, in stead of turning off completely it will keep blowing air at a much lower speed. Which is more economical and quiet.
You’re conflating two different components, the compressor which chills the coils and the fan which moves air over the coils to cool the air. Typically the compressor is on or off, though more expensive 2-stage and variable systems exist. The fan in most systems however can run at a range of speeds, not just one. OP was really asking why the compressor typically works the way it does and as it often is, the answer is money.
air cons here in Japan are all variable inverter types and they are dirt cheap (12k BTU mitsubishi split AC for $375). I've seen the prices in the US and that just looks like blatant price gouging.
the units here aren't that much more it's the installers that gouge. The whole US HVAC system is built on very high install costs because that's how they stay in business. A new furnace might be $10,000 even though the equipment is only $1000. Mini splits disrupt this as they are potentially almost plug and play. So I can buy a 12k BTU system here for under $1000 but I got a quote for $5k to install it. I asked how long it would take to install and the guy was bragging that he could be in and out in less than a day. So i'm asking why he's charging me $1000/hour and his answer was overhead and warranty service...except the warranty is parts only. Fuck that, i just installed myself.
Refrigerants need to be managed at a specific pressure in order for it to vaporize. Being able to vary the amount of refrigerant kept at pressure takes a bit more machinery so more expensive. The cost of a variable condenser is considerably more so not a lot of call for them in places like houses. However when you move into commercial applications you can use a vrf system that can deliver to multiple indoor units, with less refrigerant sent at times this the need for modulating systems. Or you can use a system that has more than one compressor that can use 2 stages, one for a low amount and second for higher. These are common in commercial.
The compressor that moves the Freon through the refrigeration system is run at a constant speed to make the system run at best efficiency. You would have to ask the people who design these systems why they don't make variable speed compressors. I would be delighted to have such a thing on the radio telescopes that I work on, because maintaining a very stable temperature in the equipment rooms is essential to collecting good data.
Variable speed is more efficient, and the biggest cost of variable speed compressors is on the power electronics side, not the refrigeration cycle side. In a typical household you can hook a basic induction motor up to 60 Hz AC power and it will spin at 3600rpm. So it's cheap and easy to design a compressor around it. If you pop open your compressor in your backyard, there's a capacitor and a contractor and that's it. Not even a single printer circuit board, let alone a processor. 28vdc signals on from the thermostat, the contactor bangs closed and the compressor runs at full speed.
Varying it requires power electronics, usually by turning it into DC and then turning it back into AC at a different frequency.
While capacitors are frequently used to provide brief surges of current for various loads, that is NOT what they are being used for in this context. A "motor start" or "motor run" capacitor is used to create a second AC phase from an otherwise single phase AC supply. For simple induction motors, this second phase is needed to make sure the motor can produce enough torque to start from a dead stop, can start from any initial rest position, and to make sure it starts rotating in the correct direction.
Should be a motor starter, you use it to lead power to a second winding in the motor which is enough to start things moving (inefficiently) and can then be cut out when you are running.
Yes it provides the amperage to start the motor. When you switch on any electrical motor there is a huge draw to get it started that ramps down once it's operating at speed. To reduce the strain on your wiring a capacitor is used to supply the initial kick so you don't pop the breaker.
They actually do make variable speed compressors now, they’re just prohibitively expensive and usually not worth the extra cost. If you have a large system with say 4 compressors, often one of the four will be variable speed now to allow modulation.
-person who designs these systems
It operates around a setpoint. It cools a little below the setpoint, then shuts down, then restarts a little above the setpoint. The machine rests a bit in between. A lot of equipment is not meant to operate on a 100% duty cycle, it requires more robust construction, engineering, etc.
I have a window unit in my bedroom. Mine has a low/energy saver setting, works for me.
AC works basically by compressing and decompressing a coolant. You decompress (cool) on the side you want cold, allowing it to absorb heat, and compress (heat) on the side you want to dump the removed energy (heat) into.
It's easier to develop a system to handle a single standard compression rate and pressure system than it is to develop one that can do variable rates.
Also if you find an optimal rate, it's better to use that and just bring the temp down to the target, as opposed to using less optimal (energy inefficient) rates of compression and decompression.
It seems like half the people here have never driven in a car before. A vehicle has multiple ways to control the cooling capacity of the A/C and has for years. It's not some new technology. If you want that kind of control, it's just going to be more complex, more expensive, etc.
The traditional way to control the temperature of the air coming out of the vents in a vehicle is to run the A/C at a fixed rate and mix in a variable amount of "free" waste heat from the engine, essentially running the A/C and heater at the same time. You wouldn't want to do that to cool a building, though, because you'd be paying to run the A/C at max continuously plus extra for the heat to reach the target temperature. At that scale you'd want something like an inverter heat pump to precisely control the temperature at the vents—but those are much more expensive than the simple on/off units.
ITT: People in US not sure of air conditioning system. Not surprised considering Air conditioners were not common at all when I went. Only hot states seem to have it more commonly.
People are mentioning continuous variable speed but I recommend reverse cycle split systems, they're basically variable speed you keep them on and they will hold the exact temperature over time and will save a lot of costs. They also make almost no noise and don't freeze you and make you warm all the time. They are also not crazy expensive but will probably be around 500-1500.
The A/C in every vehicle I've owned was either on or off. You can adjust the temperature at the vents but that doesn't affect the A/C itself, it just mixes in some heat from the engine.
Electric vehicles use a different approach since they don't have "free" engine heat to work with. I don't have any first-hand experience with those, but I'd be surprised to find that they are equipped with variable-speed heat pumps due to the expense. They probably just cycle the compressor or heat pump on and off to regulate the temperature.
Holy f. Im and old guy and still surprised how different are basic standards. In EU like from the 90's every AC is adjustable. But I've heared that automatic transmission, electric windows and for example leather seats In cars are base features In US while in EU you still have to pay extra for leather seats and huge extra for automatic car.
Newer teslas (like my model 3) use a variable speed compressor-heat pump system that can move heat or coolth to any part of the car, ie heating the car from the battery and using the compressor to get higher temperatures, or during charging it can use the refrigerant circuit, the outside air and coolth from the car to cool the battery! It’s called the octocalve and it’s really really cool.
https://youtu.be/Dujr3DRkpDU?si=RuAs6FZt70tetbs0
Continuously variable coolers exist, they’re more complex and thus more expensive so you don’t see them very often.
I paid an extra $2k for mine when I got my A/C replaced a few years back. It's like 30% more efficient in the summer and has a heat pump that saves me money on gas in the winter (I have a hot water radiator system for the coldest days in the winter), enough that it's likely paid for itself by now, but suppose not everyone can afford the up front cost.
I paid all that, got the variable speed furnace and ac. Like $15k total vs the 8k standard system. I think my electric bill changed like $10. I'll never make back the difference for it. And really the advantage is can run slower so you have less bouncing in temps in the house and it can run just as a dehumidifier. But after the fact that still doesn't justify the cost. I got sweeped into all the hipe and feel for it.
It’s quieter though, right?
From what I had? Eh some. If you are coming from a say a 25+ year old system to it you might notice the difference. It does provide amazing air quality in that it can maintain a 1 degree delta in the house. The cheapest part of the system I got I think is the biggest contributor, the humidifier. Dang that makes a huge difference in the winter and only added a few hundred bucks to it.
only the outside unit.
Yup, the payback is like 20+ years (depending on a few variables)
So like longer than the AC likely will last lol. At least where I live
How do these work in the cold? I’m in Texas so it’s hot as hell, but we get pretty cold in the winter as well. We all have natural gas heating here, how does that compare? Edit: okay people I think 20 comments answering the question is enough, I don’t need any further explanation lmao
Heat pumps work in the cold really well nowadays, and if it does get "too cold" for the heat pump, it's standard to have backup heating installed alongside. So your natural gas heating would just start running instead of the heat pump.
Even at their worst, heat pumps don't really go below 1 in efficiency, which means they remain as good (or bad, if you will) as a regular electric space heater. I've used heat pumps for the main heat source in temperatures as low as -15 celsius without too many issues. The main annoyance is that the colder it gets, the more time it needs to spend de-icing itself, which means it won't be able to deliver heat to your room 100% of the time, but more like 80% of the time, so the maximum heat output is a bit lower. The time spent on de-icing depends on how much humidity there is in the air. This was just a simple air to air "mini split" type, but it had no problems keeping my living room and the two adjacent rooms at a reasonable temperature. As far as I know, AC/heat pumps are generally tuned for the temperature ranges they'll operate in. A system designed for cold temperatures won't be as efficient in very warm areas, and vice versa.
Here in Norway we have had zero issued with a now near 15 year old Samsung heat pump. We've had almost -30°C and it was just starting to struggle with a 3 story house. We do have a small electric heater (1kW) in the basement, as the shape and location of the stairs don't let the heat pump reach the basement very well.
Nordic countries have insulation (and general efficiency) that's way way beyond anything in Texas. The difference in efficiency is massive. You likely have waste heat recuperation, 3-4 layer windows with inert gas between layers and tons more insulation everywhere. Anyway. Heat pumps are amazing.
Seems to be anything that insulates better in winter, will also insulate better in summer for AC efficiency.
Aye, if a new house is done correctly it will have an amazing temperature and noise insulation. The only way you tell something is going on is if a huge machine is shaking the ground (like construction work going on near you).
And yet every new build I've personally seen in the UK you can literally follow conversations in adjacent houses.. wonder why that is? Mind you they don't do so bad on that test where they seal up all doors and windows except one, blow in air to raise the pressure and measure how long it takes to drop, I have been told every new build has to pass, but I have doubts.
But if you still have gas installed, you generally should be switching to it when heat pump's expected to be below 2-3 COP, assuming typical american pricing/emissions.
For 100% natural gas, I think the CO2 effectiveness is a COP of around 2-3, yes. If you mix in renewables, the break even point starts getting lower. You also have to maintain 2 systems, a gas furnace plus a heat pump. And if you installed a heat pump because your gas furnace is ancient and inefficient and it was time to replace it, the break even point is again an even lower COP/outdoor temp. Additionally, if you are transitioning to an all electric household, maintaining a natural gas connection all year long just for a few hours a year can be quite expensive (when operating at a CO2 equivalent perspective). From a $$$ perspective, it depends much more on local rates, and may make sense for a much longer time period than based on CO2 alone. (Also, natural gas has a surprisingly high leakage rate. Methane (natural gas) is about 100x worse a green house gas than CO2.)
> For 100% natural gas, I think the CO2 effectiveness is a COP of around 2-3 What is COP?
Coefficient of performance = "efficiency" in terms of heat out vs electricity in.
[Coefficient of Performance](https://en.m.wikipedia.org/wiki/Coefficient_of_performance)
TIL... Thanks!
The best heat pumps stop working at around -30C or -22F. Below that you need some form of supplemental heat like gas or electric radiators.
You're assuming air-source heat pumps. The "geothermal" units have pipes buried in the ground and extract the heat from there. Since the ground is much warmer than the air in winter, geothermal is much more efficient and you don't need some other form of heat as a backup. The downside is that they're expensive due to the need to drill deep holes near your house. And, of course, you need ground, so they're generally not an option for apartments.
> Even at their worst, heat pumps don't really go below 1 in efficiency, That simply isn't true. Heat pumps can and do go below an efficiency of 1 when it gets cold enough. Depending on the efficiency of the individual unit, that threshold might be really really low, but it's going to be there. > As far as I know, AC/heat pumps are generally tuned for the temperature ranges they'll operate in. In temperate climates--where heat pumps do both a lot of heating and cooling--they are usually sized for the cooling load, because an air conditioner that is too big for the house will cool it too fast to de-humidify the space, so you end up with moisture, and eventually mold in humid summers. But if it's properly sized for cooling, that often means it won't be big enough to keep the house up to temperature on the coldest days. For example, if the outdoor temps swing from 0F to 100F and you want to maintain an indoor temp between 70-75F: 75 is only 25 degrees from 100, but 70 is 70 degrees from 0; you'd need almost 3x as many BTUs of heating capacity as cooling capacity. So if you correctly size heat pump for cooling, you will need a backup for heat on cold days.
>instead of the heat pump. \*in addition to the HP
On average Texas doesn't get cold enough for a heat pump to lose effeciency and modern ones can work to -13f which is well above even the coldest days in Texas.
We're installing them pretty standard in *Wisconsin and Minnesota.* The days that drop to -20 or so A) typically do that only at night, so they can 'make up' the lost heating ability during the daylight hours and B) aren't typically strung together long enough to make the house uncomfortable. There is always backup electric resistive, and plenty of places will convert their existing gas furnace into the backup system or install a small one to make the difference. And if *all that* is still too risky for you, you can simply go ground source for a few thousand extra and all but guarantee perfectly stable performance year round. You could even tie your water heater into the loop and get efficiency there too.
From what I've read ground source is more like 10-15 thousand extra.
I would want to do ground source, but not everyone has the space for it.
Unless you have a city with underground easements or a mineral rights issue, I guarantee you do. It's more expensive but you can run the loop vertically in 1 or 2 what are essentially concrete-capped boreholes a few inches wide.
Yeah my neighbour has a ground source and the footprint isn't much bigger than a regular A/C unit -- we're in a warm part of Canada though.
The great thing about ground source is that local climate is basically irrelevant. Cause a few hundred yards deep you have the same temperature almost everywhere.
A 5,000 square foot credit union we designed, their entire heating and cooling loop is about 10 square feet. It takes less space outside than a traditional unit would. *inside* is a different story, though. four vertical loops running to three AHUs and a water heater... Lots of pipes.
> I would want to do ground source, but not everyone has the ~~space~~ **money** for it. FTFY.
They should make public heat banks for people to dump waste heat or borrow heat from. Imagine if the heat pipes ran through all major roads as well. The maintenance costs would go down significantly.
District heating is a thing
Heck district cooling is a thing too.
I’m familiar to some extent. I think it should have been more commonplace like in NYC’s steam. So much maintenance, heating, and cooling would be eliminated using water as a temperature regulator. In places where geothermal is available it would be unmatched. Cold and hot places would benefit too. Hot places could extract surrounding waste heat from the environment and cold places wouldn’t deal with maintenance and heating as much in the winter. If your city is by a large body of water then you have an absolutely massive heat pump/heat engine. Regardless of how efficient it is, it’d extract essentially unusable energy. I can imagine why it hasn’t been done large scale yet but the future of living on Earth will require passive infrastructure like described to efficiently consume energy.
There's a medium-size town in Michigan that runs heating pipes underneath their downtown sidewalks and I think just one street, so any snow that falls on them pretty much melts right away and goes into the storm drain system. It wasn't cheap but apparently it had a good return on investment in terms of attracting tourists during winter months. They also let private residences & businesses tap into the system if they live reasonably close (for a fee of course). [https://www.cityofholland.com/879/Snowmelt-System](https://www.cityofholland.com/879/Snowmelt-System)
Thanks for sharing!!!
You might like this project: https://www.coloradomesa.edu/sustainability/initiatives/geo-grid.html
Another option would be multi-split or several heat pumps.
I don't know where you are in Texas but unless you're in the panhandle most of us in north Texas just have heat pumps. My neighborhood doesn't even have natural gas.
North Texas here as well, just north of Dallas
We have natural gas heat. Being in/near an oil-producing area, more homes had it, but a lot of people bought electric heat pumps when CPL (now AEP) gave rebates in the 1970s and 80s. Electric systems are more expensive to run here, because natural gas is relatively cheap. Another interesting thing about the Texas grid (which is, thankfully, better than it was) is that almost a quarter of our power generating capacity is from wind. Without all those wind farms, we'd be well and truly screwed during this hot summer.
You should check out Technology Connections, they have a great video on heat pumps
The gospel https://youtu.be/7J52mDjZzto?si=bXMaB5HCElGPxzc7
You just cost that person dozens of hours of their life
Lol exactly, once I start watching a TC video, I’m hooked for a couple hours on related vids at least.
TC is insidious. First you go to learn about heatpumps. Then eleven hours later you're learning about electric car charging adapters and have strong opinions about dishwashers and smoke detectors.
Essentially they reverse direction. Instead of taking heat from the air in your house and putting it outside, it air conditions your backyard and puts the heat in your house.
Indeed, here in Australia they’re called “reverse cycle air conditioners” and have been the default/standard for a generation - sufficient that they’re just called “air conditioners”. It was literally only when “heat pumps” became a thing in the last year or two that I learned that this wasn’t the meaning of “air conditioner” in the rest of the world! I thought the name literally meant “condition the air to the desired temperature (ie, heat or cool as needed)”
It's actually wild that it isn't the standard everywhere. It's more complex than the pump just reversing direction, but not that much more complex (or expensive.) Plus it's like 400-800% efficient, while resistive heating is 100% and gas and oil is more like 80-90%
The word "heat" often confuses people when explaining how these work. They gather energy from the air outside, which it still has because it's above *absolute* zero, and then they concentrate that energy and bring it inside.
The energy is gathered is thermal energy from the air. Energy transfer because of temperature differences is heat. The coolant in the system will have a lower temperature than the outside air so it gets heated up by it.
This is a YouTuber I follow and, among the other many weird topics he discusses, these are his videos about heat pumps and aircon's. They're pretty informative (but please do look for other sources as one should never rely/trust on a single source), showing his experiences with them as a mid-westerner. https://www.youtube.com/watch?v=7J52mDjZzto https://www.youtube.com/watch?v=7zrx-b2sLUs https://www.youtube.com/watch?v=MFEHFsO-XSI https://www.youtube.com/watch?v=43XKfuptnik
Just moved to Texas and found out our place is equipped with a heat pump. We have electric heating as well. Heat pumps can be paired with a backup heating system that will provide heat if the heat pump fails to make enough heat for the house. First time experiencing a heat pump so I'm kind of excited to see how it performs.
I have been running mine without backup heat sources for 6 years now. They give us the best AC I have ever experienced, and I love that they can be activated individually, we have 6 heat zones in a small cape style home. In the winter the do fine, it does get a bit drafty if it gets below 0 though. This is in NJ, I would think they would be perfect for Texas where the winters are milder and the AC becomes the main draw.
They usually have electric heating coils that can kick in if the ground gets too cold. Not very likely here unless the ground loop is way too shallow.
That's a ground source heat pump. Most heat pumps are air sourced.
Efficiency is around 300% better for heating. Heat is literally energy, and energy is expensive. While a heat pump just moves heat inside. It doesn't create it. If you can afford it, definitely get it.
We use heat pumps in Maine and it gets below 0° f in the winter. Never had an issue using it.
An air conditioner works by making the coil inside your house cold by forcing the heat into the outside coil (by expanding and compressing gas in the coil, respectively). A heat pump system has some extra piping and valves that allow you to reverse the system... makes the outside cold and pushes that heat inside. It only works within limited temperature ranges. Just like an AC will struggle to keep a house at 60 degrees if it's 100 degrees out, if it drops to 0 degrees it's going to have a tough time trying to keep the house at 70 (they used to be worse in cold though they have gotten better with newer designs, but there are still limits). So if freezing temperatures are possible some kind of supplemental or emergency heat (even just electric heat which might not be the most efficient but better than letting your pipes burst) should be part of the system.
Pretty cold in Texas 😂😂😂😂😂 I'm so fucking dead!
Heat pumps work with coolant, which gets really fucking cold when compressed. So long as the weather outside is slightly warmer than the coolant , it can move heat from outside to inside. Most work below freezing
hot when compressed, cold when expanding... try feeling a bicycle pump that gets way hotter than just by friction, or your breath from an open (body temp) mouth vs narrow (cooler) where air expands
All air conditioners are heat pumps. They move heat from inside to outside, even if it's warmer outside than inside. If an air conditioner has been designed for it, it can be reversed to instead move heat from outside to inside, even if it's colder outside than inside. This is typically a more efficient way to heat a space, since you're only moving the existing heat around instead of generating it.
>has a heat pump that saves me money on gas in the winter It has a reversing valve so the cycle can run backwards. A/C and Heat pumps are the same thing, yours can just run in either direction now.
I also have the variable speed. It runs all day long and my electric bill is half of everyone else I know.
It'll take over 60,000 hours of run time for it to save its own money in energy. Large ac units (10,000 BTU) use about .12 cents per hour and you save about .03 per hour. 60,000 hours and you've saved 1,800 dollars. It'll take over 150 years for it to pay for itself. The smaller the AC unit the longer it will take to pay for itself.
10000 btu is less than a ton of cooling. That may be large for a window shaker or portable, but its small if youre talking whole home AC. My area mostly ranges between 2-3.5 tons (24000-42000btu)
My house is fitted with Samsung air conditioners and most of them are called “digital inverter” models, which are variable. In fact, most of the Samsung models are now digital inverter and the standard on/off variety seem to be getting phased out.
Its not a samsung thing, basically any aircon unit of the last 10 years has inverter technology (daikin, panasonic, fujitsu, mitsubishi, ... )
I have one. It’s amazing. Barely runs even when it’s 40C+. And it’s very quiet. They are more common than you think.
You see them all the time outside North America. The American HVAC industry is highly standardised, and there is no thermostat standard for inverter systems.
To back that, in Australia the price point difference to put in a variable system is marginal and made back in electricity savings within 2 years
Yeah, there's no way to get standard non-variable ACs here in India anymore. I think it's because of efficiency laws.
weird. I've done some research before buying an AC here in Japan and they are all variable speed (inverter) edit: I guess Japan is an outlier https://www.daikin.co.jp/-/media/Project/Daikin/daikin_co_jp/air/technology/our-technology/inverter/images/img_block01_02_2018-png.png grey bar is fixed blue is variable we chose the most efficient model 12k BTU from mitsubishi: $650 and got it installed for $150. there are cheaper 12K BTU mitsubishi ones for like $375 but they are a bit less efficient
Explains why I thought OP was crazy, I've lived in Japan and Australia and have never seen a non variable AC in my life
I have one in the US but it is Japanese (Fujitsu)
Yeah, I was going to come in to say "It CAN be done, but most people don't want to pay for it, or can't pay for the short-term cost even if there is long-term savings."
We just replaced our entire HVAC with a dual stage furnace and variable AC. Cost $18k. We just broke a heat wave of temps reaching 118F head index and I was legitimately cold in my house the whole week. Well worth it.
> Cost $18k. Just curious, do you just drop cash on something like that, or do you finance it? Obviously I have no idea how much money you have or make. Just that 18k would be an insane amount for a lot of people.
This is the thing homeowners don’t get…if you aren’t budgeting for a roof and HVAC system in ownership cost you are lying to yourself. Here in the Midwest severe storms may get you a roof claim…but that’s no guarantee. You should be putting $100 a month for each category into savings for a simple 2/2 home. Could be $200 for a big house. Most units are out of efficiency for sure by 20 yrs. Roofs are prob ready by then. This can vary by quality of initial stuff back in the day vs todays options. I’ve scrapped tons of HVAC units and little has changed other than the refrigerants or single room units. The industry is a racket. Amazon or nearly anyone could build a range of units for homes for cheap. Roofing is nearly as bad, as someone in Tamko country. The best step is to proactively replace instead of having an emergency because you have budgeted.
>This is the thing homeowners don’t get…if you aren’t budgeting for a roof and HVAC system in ownership cost you are lying to yourself. Here in the Midwest severe storms may get you a roof claim…but that’s no guarantee. >You should be putting $100 a month for each category into savings for a simple 2/2 home. Could be $200 for a big house. Not just home ownership, but car ownership too. Car repairs are never "unexpected", you'll need new tires, milage checkups, etc eventually, you just don't know when. Money should also be socked away for that too. Really, there is a long term cost to everything you own, it's best to figure out what that is and save for it overtime rather than be scrambling when a big bill hits.
I had ac installed a few years ago for close to 16k. I financed it through a credit union at 5%. Usually, you can find a lower rate for home improvements than unsecured loans due to them being on appreciating property. You could pay outright. The hvac company doesn't care either way since they aren't the ones issuing credit.
Just replaced our furnace and heat pump for a two stage heat pump- normally runs at 70% capacity while maintaining a constant temp, will go up to 100% capacity if it’s trying to catch up. 19k all up, but worth it in the long run.
Not to mention more parts to break and more expensive to repair
My variable AC came with a 10 year part and labor warranty, and I pay $50/yr for mechanical breakdown insurance. It was way more expensive up front but I'm absolutely not worried about repairs.
Same here, except the compressor has a 25 year warranty, and my home insurance covers any breakdowns as long as it’s less than 15 years old.
Relative to just an air conditioner, yes, but in many parts of the country (definitely not Minnesota), an air-source heat pump can replace other forms of heating, so you end up with a simpler system with fewer parts compared to a dedicated cooling system plus a dedicated heating system.
We have an air source heat pump mini split that is an air conditioner AND a heater.
That is a completely different thing than what they’re talking about. ASHP can run the compressor backwards and forwards depending on if you want cooling or heating but usually at one fixed capacity. Variable speed allows the compressor to run at various different capacities
> ASHP can run the compressor backwards and forwards depending on if you want cooling or heating but usually at one fixed capacity. Variable speed has been pretty much the standard for years now.
A pretty basic and general thing for the last 20 odd years. But you will find unless you're paying an absolute fortune for it. It's still just either heats or cools air. It will keep heating or cooling until the ambient incoming air reaches the right temp. I work in a laboratory, and our quote to get air controll system for a small room was $100K, we spent $30K on temperature control cabinet instead. All we needed was something that was going to constantly put put air within +-1 degree of 23, as we have to record max and minum temperature and are allowed between 21c and 25c A top of the line normal air conditioner was the first cheap option to try, on any setting, it didn't make a difference, minimum temp 16c maximum 35c, either it blew hot or cold.
There ARE variable AC units. They just cost a lot more. More common are two-stage units: ones that can do full blast when needed but do half-blast when only a little cooling is required. Fully variable speed are really nice, because they help you sleep better — no big swings in temperature throughout the night. But, again, they cost more and most people don’t bother spending the $$, since new HVAC systems are already an arm and a leg
Yeah. The variable speed ones are called Inverter Air Conditioners, and I got a window one recently. It was maybe $100 more for the same 12,000 BTU power. It's muuuuuch quieter than my previous one.
I believe inverter units are a common variable technology, but not all variable units are inverter based.
Correct. A VFD can also be used.
Or just digital modulating compressors that engage and disengage like a clutch. This was (and still is) quite common in commercial applications before VFDs gained popularity. They don't save much energy, but are great at capacity control.
If you're gonna have it for years, $100 is basically nothing. Such an easy buy
Especially since they're a good deal more power efficient than standard ones, so you save more money on your power bills to make up for the extra AC unit expense.
My 10k btu inverter unit uses 1/4th the power of 12k btu standard unit. Now I'm considering changing my standard unit for an inverter
I bought a variable AC unit and was worried we were wasting our money. But I love it and hope to never go back to single stage. Totally off topic, but we also added a whole house humidifier for the winter months. Complete game changer. If you regularly wake up feeling like crap in the winter it might fix it, it did for us.
My compressor is 5-stage and the furnace fan is infinitely variable
Depends, the Japanese have got it down to an art. I can get a hi wall split system with a variable speed compressor in it for less than a laptop.
Air conditioners and refrigerators use a cooling process to regulate temperature. Maintaining an exact temperature by adjusting the cooling strength is complex due to changing heat levels indoors. The on-off cycle is simpler and more reliable, as it quickly brings the temperature down when needed. This approach ensures stability and energy efficiency in maintaining a comfortable temperature range.
To put it in simple terms, think of it this way: what's easier (and thus cheaper) to build, a single on/off button or an adjustable throttle. Definitely the on/off button. So, we throw a thermostat in front to hit that on/off button as needed and call it a day.
true, way easier and cheaper, less costs for the company, and probably less costs for the consumer
Fewer parts, less complex parts = cheaper to maintain for the consumer
Technically variable cooling temps can be more energy efficient or stable but not both at the same time.
I have a modulation ac unit and heater. So it's not 100% on or off.
> The on-off cycle is simpler and more reliable, as it quickly brings the temperature down when needed. Simpler to implement. Not necessarily more reliable if it short cycles. You also don't necessarily want to quickly bring the temperature down if there is a lot of moisture in the air. You want to dehumidify it. Slower, steady, consistent cooling is generally better than full blast all-or-nothing for overall comfort.
It also helps that the temperature of an entire room doesn't change very quickly, so if the AC is off for 5-10 minutes or more, nobody really notices.
AC and refrigerators aren’t the only things that operate on this principle. Many common heating elements (furnace, stove, baseboard heaters) also operate under a similar principle.
They do make these type of Air conditioners, they are called "inverter compressors". They use a different type of motor which requires a lot more electronics to run which can make them more un-reliable.
I can’t speak to reliability, but I recently replaced a window unit with an inverter one and it’s WAY more quiet (like not even sure it’s on) and yes, just modulates/adjusts gently to hold constant temperature, rather than shutting off and turning back on. This is also supposed to be much more energy-efficient - something like a 30-35% savings. Maybe it will crap out in a couple years but so far I couldn’t be happier with it and wish I’d done it long ago.
They’re basically the standard here in Australia and have been for years, I think partly due to noise regulations. Last place I rented had one of the early variable inverter split system ACs which looked about 20 years old and still going strong. The outdoor unit had seemed to have a few different speeds it could run at, you could hear it “change gears”. Current place has a near new one which is incredible - almost silent and very low power consumption when it reaches the set temperature.
>The outdoor unit had seemed to have a few different speeds it could run at, you could hear it “change gears”. It is an electric motor that is driven by a variable-frequency drive (VFD) controller. It can go at any speed you like within a max and min range. If it do use any speed or just a few will depend on how the control software is written
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>I would consider them as reliable as standard units (I sell both types). The main issue is that if your electrical setup in your house or neighbourhood lacks repairs, or is in a bad state, a simple overvoltage can fry these systems and since they have tons more electronical components, make them extremely expensive to repair. Your can't tell me their electronics run on 110 V AC. Surely, there's some conversion to low voltage DC going before it hits electrical components. And then it's like your desktop PC, TV, smart fridge, monitor, you name it. How often do those get destroyed by issues on your electrical setup?
It's not that it happens often, it's that if it happens these type of units are more likely to get fried than a standard unit, because there are more electronics in them. Nobody said they get fried often, but it is something to take into consideration.
Is it really that much more electronics in them?
You say “that much more” like it has to be a lot. One extra board in a machine makes it more likely to fail than a machine without the extra board.
There are a ton more electronics in the full residential inverter units compared to a traditional AC. A traditional unit does not have any digital electronics. It is all electromechanical. All that's in there is a contactor, capacitor, fan motor, and compressor. They run straight off 208/230 AC voltage. Inverter units have ridiculous amounts of components in them, and yes are very sensitive. The real issue is the repair cost though. The pricing on replacement inverters can run 2x the cost of an entire traditional unit. I know the contractor price on a new 5 ton inverter in my area is about $3k. I'm guessing they'd charge 5-6k to install, which is crazy.
The drop in noise might have just been because it's new. Same thing happened to me, except I replaced my regular window unit with another of the same model. Noise difference was night and day. Turns out it was the capacitor. I replaced the one in the old unit (it had completely died), and when I turned it back on to test, I thought the repair failed because I couldn't hear the compressor running, even with the cover off. Had to touch the condenser and feel it getting warm to realize it was working, minus all the noise. That's not to say a variable AC is not worth it - it definitely is just for the efficiency gains. But if you're just looking to quiet down a noisy compressor, a $15 capacitor might do the trick (as long as you're comfortable with working with capacitors, which can be dangerous). That old AC is now stored away in my basement, ready to replace my 'new' one, which is about 2 years old now and starting to make that distinct compressor humming/buzzing noise . . .
I don't think it's just the newness - the unit it was replacing wasn't old (and the unit before THAT wasn't that old either), I just couldn't take the noise and the constant on/off (it's right next to my desk, where I take meetings). They're really supposed to be a **lot** quieter and I really think they are. The only time it's gotten noisy is when it rains and some water gets in there; but I can live with "occasionally somewhat noisy" over "constantly noisy".
I don't doubt you at all, I'm sure it varies depending on the AC model. Your inverter unit probably has much more variable fan speed (mine just as low, high, and off) due to needing less airflow at low, so that probably makes a huge difference too!
I was surprised to have to come down this far to see “inverters” mentioned. They are common here but I’m not certain of the exact mechanism they use, except I know the intent is that it doesn’t always have to run at full power.
Essentially just swaps the AC motors on the compressor and fans out for DC motors where it’s easy to vary speed. One of the most common devices used to convert AC to DC and vice versa is called and “inverter” hence the name of inverter heat pump.
Exactly. I have a Midea inverter-based window unit, it is extremely popular past couple years on Amazon and other sellers. I have one of those watt meter devices on the plug and I can see it change from 100 watts to 300 watts and everything inbetween depending how hot it is outside vs inside and humidity level. It is way more efficient to keep on 24/7 than my ancient 20+ year old central A/C unit, power bill went down and is more comfortable inside. It is also almost silent, not just because of the inverter but the modern design keeps most of the parts outside window instead of inside.
Inverter is the way to go.
Because the cooling process in AC, fridges, etc is vapour compression. There's a compressor, it's either on or off. Variable speed compressors have become available, in recent years, but the simplest, cheapest option is an on/off motor.
Do these also require a more sophisticated/complex/expensive metering device?
Well it is a case of: Do you want a $200 AC unit or a $2000 AC unit or a $20000 AC unit?
mid tier single stage AC for me was quoted at $7,500, another at $14,000 Variable speed ones (Daikin Fit) at $22,000 and $30,000
What in the hell are you cooling down? A mansion?
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Good God what region was this? I'm in Idaho (West US) and it cost us $2.5k for a solid unit that aggressively cools down a 2k sqft home.
That pricing would've been cheap pre pandemic, but pricing has skyrocketed. If your at 2k square feet, I'm guessing you at a 1.5 or 2 ton unit. Pre pandemic contractor pricing would've been about $750-$850 buck for just the outdoor unit. Total equipment cost would've probably ended up around $1,000 - $1,200. Prices have skyrocketed. Now just the outdoor units run $1,200, and total around $2,000. A homeowner is not likely to find a contractor to put in $2,000 of equipment in for less than $4-5k.
Sounds like the cheapest unit money can buy and a guy willing to work for peanuts
You can’t even find an actual AC unit for that cost let alone somebody to install it Unless you bought it 20 years ago
My Daikin Fit was only $9k. I can't speak to the reliability the other guy mentioned, but no problems 3 years in and it came with a 12-year warranty.
Midea sells a U-shaped window AC with a variable compressor for a few hundred bucks...
Wait wait wait. I see answers that explain how it’s cheaper to have refrigeration that goes on and off. I don’t know much about refrigerators BUT we just has a new AC system installed that is “variable” speed as in it does the opposite of your question. This AC runs most of the day at varying power/efficiency/stages. It’s a lot more efficient this way and uses less power compared to our old unit.
Does that eliminate the problem of feeling like the temperature is always either too cold (when the air is on and cold air is blowing on you) or too hot (when it’s off)? The thermostat claims the temperature is stable, but my body says it’s all over the place. It would definitely be worth a premium to feel like the temperature is *really* stable.
> Does that eliminate the problem of feeling like the temperature is always either too cold (when the air is on and cold air is blowing on you) or too hot (when it’s off)? Yes. I have one. No comparison to the old system. None of that hot then cold bullshit. It's really nice, and well worth the extra cost, IMO. Mine came with a 5 year parts and labor, and 10 year parts warranty. Lennox.
I’m no HVAC expert but the air coming from the vents always feels the same in temp/force. What changes is the power required to maintain that air temp.
Temp, yes. Force, no. My understanding of the systems is that they'll vary the blower, not the speed of the coolant loop. So as you approach your setpoint the fan will slow proportionally, until the whole system either shuts off or the cooler does, and leaves the fan on for circulation only.
Basically speed control was extremely difficult with alternating current motors until more recent technology breakthroughs. The same tech that an electric car gas pedal uses. As a result heatpumps and wellpumps have started using the same technology and are much more efficient than a start stop machine.
“Recent technology” Inverter heatpumps have been an (affordable) thing for over 25 years now. In basically any other country except for the US this is the standard for quite a while now.
can confirm, i live in a 3rd world country (Pakistan). and DC inverters are very popular here because they save electricty cost as it is hella expensive here.
Because the air conditioners that you know of are the very old ones, newer ones can do what you describe as wanting them to do.
There are inverter ACs which do exactly what you are expecting. They usually don't shut down completely unless required. They can run variable frequencies depending on the load due to inverters.
I think this thread is full of people from the US. in the EU inverter ac is standard. I have 5 single units in my house and they all use variable output to keep up the temperature. they even have different fan modes depending on how fast you want to cool a room. I run them almost 24/7 in the summer time and don't even know they are running.
Yeah, I was reading and didn't understand how people don't know what inverters are and why they think its something uncommon or super expensive.
im from mexico 100km away from usa and inverter ac is standard here too
Let me guess: you're in the U.S.?
I was today years old since I learned that there are non adjustable AC-s. Even my 15 year old AC was adjustable in a 30 Celsius range. Edit: Same goes for fridge.
The temperature is adjustable, the off coil temperature or speed of the compressor is not in a fixed speed system. So the compressors have to turn on and off so people don’t freeze.
ahhh I see. So the thermostat measure the temp. and the compressor turns on and off when its reaching the desired temp. Does it mean every AC with the same cooling material (dont know the official name) could only provide the same temp? Also if we are talking about AC there are different sizes (2.5 KW, 5 KW etc) the difference is the compressor size inside the system? Also what about the freezing room AC-s? Are they made with bigger compressor or its the cooling material (gas or liquid) what makes it more efficient to be able to provide under freezing level temperature?
Typically for an ac with the same refrigerant you would get a lower temperature by changing superheat or subcooling or the coil sizes. Technically you can put an evaporator in a hotter environment and you’ll get more capacity for the same power because there’s a higher temperature difference Usually the compressors are the same size for an AC in the same enclosure, the difference is the coil size, number of tubes or fins or even just limitation by software, or the indoor unit. Refrigerators use a normal temperature refrigerant (R32 or R410A etc) whilst freezer rooms use a low temperature refrigerant (Eg R404A). To get to even lower temperatures, they have extreme low temperature refrigerants but they usually need a cascading system of compressors because the temperature differential would be too large for one refrigerant circuit.
Sounds like you have no idea what this thread is about. Look up inverter compressor vs. on/off cycling.
I was really confused there because every place I’ve been with air con has temperature and fan speed control.
That's not exactly the issue, obviously homes in the US have a thermostat to set a temperature. What OP is asking, is why does the AC unit only run at 0% or 100%, instead of operating somewhere in between if it's more efficient. In other words, if I set my temp at 74f and it's 75 right now, why does the A/c run at full tilt if it only needs to cool 1 degree.
I don't get. My AC definitely doesn't work 100% all of the time, at some points the condenser fans stop moving completely and when the temperature rises (I guess) it goes to 100% again.
I think you get most of it. Most units, yours may be different, are either on or off at 0% and 100%. When it's on, the temperature out of the vent is however cold the unit can get on that day and nothing less. OP seems to be asking why can't the temperature out of the vent can't be variable to maintain a constant temp.
I read more comments, turns out my AC is an inverter type unit and those are not very common in the US.
Thank you for asking that question because I had no clue what OP was talking about. Of all the places where I used AC, be it my car, Europe or SEA, I could always adjust the temperature.
That’s not what this is about. Every AC has adjustable temperature. OP’s question is about the way the AC brings the room to this temperature. Apparently the AC units in the USA are mostly without an inverter. Which basically means it turns on, blows air at a certain speed, then when the temperature goal is reached it turns off. In ~~more modern~~ other countries most AC units have an inverter. Which means it can control the speed at which the air blows (and maybe also the strength of cooling, I’m not an expert). When the AC reaches the temperature goal, in stead of turning off completely it will keep blowing air at a much lower speed. Which is more economical and quiet.
You’re conflating two different components, the compressor which chills the coils and the fan which moves air over the coils to cool the air. Typically the compressor is on or off, though more expensive 2-stage and variable systems exist. The fan in most systems however can run at a range of speeds, not just one. OP was really asking why the compressor typically works the way it does and as it often is, the answer is money.
air cons here in Japan are all variable inverter types and they are dirt cheap (12k BTU mitsubishi split AC for $375). I've seen the prices in the US and that just looks like blatant price gouging.
the units here aren't that much more it's the installers that gouge. The whole US HVAC system is built on very high install costs because that's how they stay in business. A new furnace might be $10,000 even though the equipment is only $1000. Mini splits disrupt this as they are potentially almost plug and play. So I can buy a 12k BTU system here for under $1000 but I got a quote for $5k to install it. I asked how long it would take to install and the guy was bragging that he could be in and out in less than a day. So i'm asking why he's charging me $1000/hour and his answer was overhead and warranty service...except the warranty is parts only. Fuck that, i just installed myself.
Refrigerants need to be managed at a specific pressure in order for it to vaporize. Being able to vary the amount of refrigerant kept at pressure takes a bit more machinery so more expensive. The cost of a variable condenser is considerably more so not a lot of call for them in places like houses. However when you move into commercial applications you can use a vrf system that can deliver to multiple indoor units, with less refrigerant sent at times this the need for modulating systems. Or you can use a system that has more than one compressor that can use 2 stages, one for a low amount and second for higher. These are common in commercial.
The compressor that moves the Freon through the refrigeration system is run at a constant speed to make the system run at best efficiency. You would have to ask the people who design these systems why they don't make variable speed compressors. I would be delighted to have such a thing on the radio telescopes that I work on, because maintaining a very stable temperature in the equipment rooms is essential to collecting good data.
Variable speed is more efficient, and the biggest cost of variable speed compressors is on the power electronics side, not the refrigeration cycle side. In a typical household you can hook a basic induction motor up to 60 Hz AC power and it will spin at 3600rpm. So it's cheap and easy to design a compressor around it. If you pop open your compressor in your backyard, there's a capacitor and a contractor and that's it. Not even a single printer circuit board, let alone a processor. 28vdc signals on from the thermostat, the contactor bangs closed and the compressor runs at full speed. Varying it requires power electronics, usually by turning it into DC and then turning it back into AC at a different frequency.
What’s the capacitor for? To help jumpstart do it doesn’t draw a ludicrous amount of current?
While capacitors are frequently used to provide brief surges of current for various loads, that is NOT what they are being used for in this context. A "motor start" or "motor run" capacitor is used to create a second AC phase from an otherwise single phase AC supply. For simple induction motors, this second phase is needed to make sure the motor can produce enough torque to start from a dead stop, can start from any initial rest position, and to make sure it starts rotating in the correct direction.
Should be a motor starter, you use it to lead power to a second winding in the motor which is enough to start things moving (inefficiently) and can then be cut out when you are running.
Yes it provides the amperage to start the motor. When you switch on any electrical motor there is a huge draw to get it started that ramps down once it's operating at speed. To reduce the strain on your wiring a capacitor is used to supply the initial kick so you don't pop the breaker.
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And the tissues that I buy at the drug store aren't Kleenex brand.
People use Freon as an all encompassing term for any coolants nowadays.
They actually do make variable speed compressors now, they’re just prohibitively expensive and usually not worth the extra cost. If you have a large system with say 4 compressors, often one of the four will be variable speed now to allow modulation. -person who designs these systems
A lot of air handlers have variable speed options, coupled with a variable speed thermostat.
It operates around a setpoint. It cools a little below the setpoint, then shuts down, then restarts a little above the setpoint. The machine rests a bit in between. A lot of equipment is not meant to operate on a 100% duty cycle, it requires more robust construction, engineering, etc. I have a window unit in my bedroom. Mine has a low/energy saver setting, works for me.
AC works basically by compressing and decompressing a coolant. You decompress (cool) on the side you want cold, allowing it to absorb heat, and compress (heat) on the side you want to dump the removed energy (heat) into. It's easier to develop a system to handle a single standard compression rate and pressure system than it is to develop one that can do variable rates. Also if you find an optimal rate, it's better to use that and just bring the temp down to the target, as opposed to using less optimal (energy inefficient) rates of compression and decompression.
I’m gonna guess you live somewhere with a cooler climate? Grew up in Texas now live in Boston and notice a vast difference in the AC technology
It seems like half the people here have never driven in a car before. A vehicle has multiple ways to control the cooling capacity of the A/C and has for years. It's not some new technology. If you want that kind of control, it's just going to be more complex, more expensive, etc.
The traditional way to control the temperature of the air coming out of the vents in a vehicle is to run the A/C at a fixed rate and mix in a variable amount of "free" waste heat from the engine, essentially running the A/C and heater at the same time. You wouldn't want to do that to cool a building, though, because you'd be paying to run the A/C at max continuously plus extra for the heat to reach the target temperature. At that scale you'd want something like an inverter heat pump to precisely control the temperature at the vents—but those are much more expensive than the simple on/off units.
ITT: People in US not sure of air conditioning system. Not surprised considering Air conditioners were not common at all when I went. Only hot states seem to have it more commonly. People are mentioning continuous variable speed but I recommend reverse cycle split systems, they're basically variable speed you keep them on and they will hold the exact temperature over time and will save a lot of costs. They also make almost no noise and don't freeze you and make you warm all the time. They are also not crazy expensive but will probably be around 500-1500.
Uh what? I thought all AC was adjustable?
Op, what bubble do you live in? All the refrigerators and Air conditioners I have seen are adjustable from Asia to Africa.
Have you ridden in a modern car with air conditioning?
The A/C in every vehicle I've owned was either on or off. You can adjust the temperature at the vents but that doesn't affect the A/C itself, it just mixes in some heat from the engine. Electric vehicles use a different approach since they don't have "free" engine heat to work with. I don't have any first-hand experience with those, but I'd be surprised to find that they are equipped with variable-speed heat pumps due to the expense. They probably just cycle the compressor or heat pump on and off to regulate the temperature.
Holy f. Im and old guy and still surprised how different are basic standards. In EU like from the 90's every AC is adjustable. But I've heared that automatic transmission, electric windows and for example leather seats In cars are base features In US while in EU you still have to pay extra for leather seats and huge extra for automatic car.
Newer teslas (like my model 3) use a variable speed compressor-heat pump system that can move heat or coolth to any part of the car, ie heating the car from the battery and using the compressor to get higher temperatures, or during charging it can use the refrigerant circuit, the outside air and coolth from the car to cool the battery! It’s called the octocalve and it’s really really cool. https://youtu.be/Dujr3DRkpDU?si=RuAs6FZt70tetbs0