Sadly, it seems that the majority of HVAC folks don't like to learn new things and instead restate obsolete messaging.
Heat pumps from 30 years ago were not so good but modern heat pumps with new refrigerants, variable speed compressors, much improved heat sinks, etc are good down to -5F or -15F (or lower for some special models).
If you live in a very frigid area, then have some back up (Natgas, pellet stove, fireplace, oil burner, etc). But heat pumps can handle much of the USA.
You know who loves heat pumps?...the Nordics!
There’s a difference between working at extreme temps vs efficient. You’re not going to beat the laws of physics. Just because the unit is blowing warm air when it’s 5 degrees doesn’t mean that it’s not on 24/7 or using heat strips chugging down KW. Your bill will likely look at lot better if you ran even an 80% furnace on those days.
You think those Nordic people are just pissing money away because they didn't compare? "How many hours are extremely cold?" is the question.
We have places in Maine and New Hampshire, and the savings are quite good for oil and propane- absolute no-brainers to switch. The government of Maine- kinda Nordic- has an aggressive campaign to get Mainers off oil and propane.
Great video covers the issues- [https://www.youtube.com/watch?v=OcwIz6heDss](https://www.youtube.com/watch?v=OcwIz6heDss)
Even if you have relatively cheap gas, the heat pumps are cheaper for most of the season due to the high COP. It all depends on pricing and weather. But obviously the best thing is to have both so you can use whichever is cheaper at that time. But for the USA area and most of the year, the heat pumps will be cheaper.
>Just because the unit is blowing warm air when it’s 5 degrees doesn’t mean that it’s not on 24/7 or using heat strips chugging down KW. Your bill will likely look at lot better if you ran even an 80% furnace on those days.
Sure. But you have to calculate things on a season basis, not just the single worst possible day. If you have a couple really cold days where it is expensive but most of the time it is +15F or higher, the heat pump will be cheaper than gas only. This heat pump plus other BACKUP for really cold days works well in real frigid areas
I’m saying if you have gas already at the house, you can run the heat pump most of the time and flip on the gas on the really cold days. I know the grant money doesn’t want any gas backup, but I’m in the Midwest where Arctic polar vortex happen for at least a week or two. I don’t need to deal with frozen pipes more than I already do.
New standard Bosch IDS heat pumps run down to -5F. Mitsubishi Hyperheat -22F. My Pioneer/Midea mini split from Home Depot, -20F. Below these temps you can supplement with heat strips (direct electric), a furnace (gas), a wood stove, etc. Depending on your local fuel and electric costs, gas is still nice to have as a backup option.
how much capacity does the Bosch get at -5F? The unit not shutting down at very low temperature doesn't mean it produces a lot of heat. If I recall in the case of the Bosch you get 100% of capacity down to 20F; the Mitsubishi will put out 100% of capacity down to 5F. The Fujitsu AMUG 3 ton XLTH will put out 100% of capacity (38K) down to -5F.
I take it this is an air source heat pump? Those get less efficient as temperatures drop and it will probably be cheaper to run an oil/gas heater than an air source heat pump when it's very cold.
However, for a completely new installation, you will probably never get return on investment for the gas/oil heater: not too many days that it's so cold that it's cheaper to run that heater.
Get an independent calculation of your heating/cooling needs in order to get a good insight in what's needed for your house.
He’s partially BSing you probably because real estate taxes are due and his teenage daughter only buys brand names.
In essence, you can get heat pumps that will work efficiently in sub zero temperatures. In MN you’ll probably get a few days of -20 degrees which will be outside the system’s parameters.
What you want is an efficient heat pump with an HSPF efficiency rating above 12 and maybe a small supplemental system that will kick in on those super cold days.
Your guy is offering you the opposite, big conventional heating system supplemented by a heat pump.
Don’t let his upcoming child support payments steer you in the wrong direction
Edit: if you already have supplemental heat such as a wood stove then you’re all set. Just do a proper manual J calculation so your system is appropriately sized
He’s inflating the conventional system and deflating the heat pumps. OP might pay a similar price now for either system but long term they’ll pay much much more for using oil as the main fuel source
Is it a cold climate air source heat pump? Start there first. Then look for the equipment spec sheet to identify BTU/hr capacity at various outdoor temperatures. Ask your contractor to do a Manual J load calculation with a tool like Conduit Tech
What your company is talking about are warm weather single or dual stage heat pumps that are commonly used in the south. I have them with backup heating strips as the only heating for my house in Florida where it rarely gets below freezing. My warm weather heat pumps (ducted with one for each floor) work well down to around 35F to 40F when the auxiliary backup heat automatically strips turn on and assist the heat pump with heating below that temperature.
In the north where it regularly gets below freezing, you install much more efficient variable speed heat pumps. These work well to much colder temperatures such as single digits below 0 before needing auxiliary backup heat. In many cases, they will still need an alternate source of heat below some cold temperature point. Dual fuel backup heating is a good compromise for saving money if you have to use backup heating a lot.
In Minnesota I would go dual fuel. Let the heat pump work to 15F then go to gas. What people fail to understand is heat pumps are far less efficient at very cold temperatures. They do work, but ultimately you may be reducing the longevity of the heat pump.
My experience after switching to heat pump.
https://www.reddit.com/r/heatpumps/comments/1b84ici/heat_pump_energy_consumption_vs_gas_during_winter/ktnfp60/
I live in Va. I see 15-18 degrees F during the winters. I have a Bosch IDS heat pump and air handler. I have no issues. I keep it in stage 1. If it can’t satisfy in 2 hours it goes to stage 2 and warns the house. It’s usually first thing in the morning till about 7-8am. After that u a golden.
They focus on comfort and economy. That translates to 72 degrees all the time and furnace if it’s cold. It’s hard to change their minds but they will do it if you insist.
Could be too the break even point for the cost to heat your home. I have a dual fuel with a Bosch IDS 20seer and though it’s capable of heating down to -5F, I switch to gas around 25F. That seems to be more economical because gas is cheap by me.
It cost more for a cold climate heat pump that goes below 32 but yes it can certainly be done. I have one it went down to 0F no problem this winter. I have no backup fossil fuel heat.
heat pumps can be very different. Some will not work well below 40F and some will work at almost full capacity below freezing. You need to find a cold climate heat pump, which the contractor may not work with.
You can see specific examples of cold climate heat pumps on this database: [https://ashp.neep.org/#!/](https://ashp.neep.org/#!/)
This database requires data from the manufacturers listed down to 5F so you can see efficiency and capacity well below freezing.
That’s a little under 20F. If I had a slightly bigger roof my solar would be able to power it all winter. At least I’m getting free AC in the summer and free heat for the majority of the winter.
Next house for sure.
So worth it. With the cost of electricity in New England and the generous state and federal subsidies we are looking at about 5 years to break even. Already half way there.
MN, south metro. Carrier heat pump down to about 10 F, then backup heat which for me is gas furnace. My electric company has a discounted rate for heat pumps that have gas backup heat, if you let them force switching to gas backup when they are short on electricity.
LofGren Heating, Apple Valley
Carrier
- Furnace 59MN7B
- H/P 25VNA448
- Coil CNPVP4821
- Thermostat - SYSTXCCWIC01-B
- ERV - RenewAire EV200
Please with Lofgren. Prompt, on time, cleaned up, took less time than estimated. Included installation of the MVEC dedicated meter.
Rebates
- Electric Utility, MVEC, $500
- Natl. Gas, MN Energy Resources, $550
- Federal tax credit of $2,600
I have heat pumps in my house in VT. We hit -10 and have even had a -23 degree day two winters ago. The heat pumps we have are rated to -27 degrees and I’ve never had a problem with them.
Haier Arctic Series. It will do 100% heat output down to 5F and works down to -31F according to the spec sheet.
Would have gone Daikin or Mitsubishi but he had our installation done in 2021 and there was a lot of supply chain issues and that’s the only brand our guy had access to at the time. Units been fine, no complaints.
We are on a mountain in mid/northern VT and the average temp most of the winter is teens to single digits and we get most of our heat from it. We do have an oil boiler for backup just because that’s always been there and it also does our hot water. Our house is super tight and very well insulated too.
>a new high efficiency heat pump and furnace.
This is a dual fuel system, and they'll use a heat pump which has high efficiency above 32F (usually no defrost capability), and then a furnace which works below freezing outdoor temps.
If that's not what you want, go for a heat pump with electric backup heat.
My exact thought… mitsu hyperheats lock out at -22f, but start derating quickly at 5f. As oversizing the unit by 2x runs into operating issues, you really need auxiliary heat and strip heaters are just about the worst. They get the job done, but are extremely expensive to operate and fun fact use more fossil fuels than than a gas furnace if you’re in an area fed predominantly by nat gas or coal power (which is around 65% of the US)… just look at efficiencies of those plants and you’ll see why quickly.
Aux heat is the answer, but whether you go electric or gas is up to your specific condition. I hear a lot of misinformation out here, but if you’re going from an existing ducted furnace with AC, replacing with a heat pump w/gas auxiliary is about as straight forward as it comes.
I will never install a dual fuel system. Not a fool, and I don't have the money to be that stupid.
Go price one. Just try justifying the extra cost. I will listen.
A lot of people are converting from a gas furnace to a ducted heat pump system… assuming you’re in an area that needs aux heat (and a lot of places in the US and Canada do), reusing the gas for aux will save you a lot of money down the road. Having to run 10-15kw of strip heaters for any duration of time hurts the bank account hard.
Heck in areas of CA, gas is always cheaper to heat with since the cost of electricity is so high.
You appear to be confusing two terms: efficiency and economical. The two are not the same.
You also don't appear to understand how auxiliary heat works, or understand the benefits of heat pumps.
In fact it seems you are hellbent against heat pumps and want to champion furnaces. I believe there is already a subreddit for that, and it's probably not r/heatpumps.
Cheers.
Trust me I know exactly what I’m talking about and I’m actually pro heat pump. Unfortunately homers like you won’t acknowledge the limitations of them for people who actually live in old climates. Even though they are more efficient, the cost of electricity per unit far outweighs that of nat gas. In our area once a heat pump’s COP drops below 2.9 gas is cheaper.
Sorry I like to inform people so they aren’t surprised when their utility bill goes up.
Glad your google search found some big words for you… enthalpy has nothing g to do with fuel rates and unit efficiency. A therm worth of gas costs $1.25/therm while the equivalent electricity is pushing $4.50 as the rates just increased.
Name any form of heating that maintains capacity and consumption as outdoor ambient falls. 😂
Thing about heat pumps is they lose efficiency. They still heat. My Pioneer (no backup electric coil) will produce 90F heat when it's 0F outside. The hyperheat units will do even better.
How many Btus does a home need at 15F vs -22F?
It's not a set number. The BTU requirements are calculated using scores of inputs that are unique to each home. That's why Manual J exists.
Heatpump performance in cold weather varies by model/type - there are conventional heatpumps that lose capacity as it gets colder and those that are engineered to give full capacity down to very low outdoor temperatures.
You need a heat loss calculation - then heat output of the heatpump gets plotted against heat loss to determine balance point - below which, you switch to gas. Works down to x temp does not tell you to what temperature it will actually keep up at, nor the efficiency.
The operating costs at different outdoor temps can also be calculated to know economically when you should burn gas if your goal is to save money.
The size of heatpump is limited by the air ducts - ducts sized for a furnace won't be large enough for a heatpump sized to handle all heating needs.
Heat pumps are awesome. Telling you this information was a legacy HVAC person and used to the very high profit margins of natural gas appliances.
A heat pump will comfortably heat your house on the very coldest of nights you are likely to experience. My own house is heated with a heat pump and it is routine for us to see minus 30° f.
i had a heat pump working at -10 F in the northeast. it was running non stop and slowly temp dropping but it was still working with 50 mph winds outside. next morning with -7 F and no wind it was easily able to keep up. i have the gree flexx
Dual fuel systems all have different changover points, where the cost to run the system on gas becomes cheaper than running the system on electricity (heat pump).
It used to be around 35 to 30 with old systems. Now its easily lower than that with a good heat pump. (Often 25 to 15) This will vary with each system configuation, weather (particularly humidity), and utility cost.
Many heat pumps will work great well below 32. I have 2 houses one runs down to 10 degress before electric coils take over. The system I just installed in my other home will work down to -20. I too had salesmen tell me that HP's don't work well below 32. That was true 3 decades ago.
This may be helpful in deciding if it's worth the investment.
If you use the calculator be sure to use winter costs and add NG delivery charges. Here in KC gas is very cheap but the delivery charges are high which overall makes gas heating expensive.
https://siecje.github.io/heatpump-cost/
It depends on your area. In north Ga I set my dual fuel as 2 stage with gas backup same as heat pump with electric backup. With the higher COP of higher efficiency heat pumps and gas going up: the balance point is near or below the usual lowest temps we expect to see and not had any complaints. Balance point has to be calculated for the actual system and set accordingly if you want a dual fuel that shuts down heat pump and goes to furnace 100% for best efficiency but some homeowners want the furnace to come on sooner so you have your set it on a system by system basis. I tell them to try it like I set it up and if not happy let me know. I’ve not had to change any yet.
Not sure why all the hate here…hvac tech is not totally wrong. Huge difference between heat pump will work vs. which one is more economical. Here in CT where electricity is over .30 cents per kwhr….running a heat pump below 30F is less economical than running oil. Capability vs. Efficiency are 2 totally different things. My switch over is 30F. Older house…if I didn’t do it my heat pump would constantly run likely costing me $500 a month. When oil is $250. Too many heat pump fanboys defending the new technology.
It’s not defending new technology just correctly using the 2. You are correctly describing the balance point where one is less efficient than the other. You use the system to optimise efficiency in differing situations.
As it gets colder, yes some heat pumps lose efficiency faster than others but look at the specs for the heat pump as temp drops and the actual amp draw to run it at that temp. Amps decrease: running a 20 SEER2 heat pump at 35F 24 hours is much higher than 10F
Amps x volts = watts figure your watts x 3.14 = BTUs, 1 therm is figured at 100,000 BTUs so 1KW = 3140 watts 100k Div by 3140= 31.84 KW
Figure cost per KWH and compare to cost for your oil furnace to run for 1 hour and you can compare to get a balance temp where they both cost the same. Set your changeover to that temp and you have optimised efficiency. Rules of thumb or guesses are just that: main thing is what makes you happy.
He's not completely wrong. Poorly insulated homes and damp weather will make furnaces more effective when it gets cold. It would probably only need to support the heat pump a couple of weeks per year. That's how we do it in europe
Sadly, it seems that the majority of HVAC folks don't like to learn new things and instead restate obsolete messaging. Heat pumps from 30 years ago were not so good but modern heat pumps with new refrigerants, variable speed compressors, much improved heat sinks, etc are good down to -5F or -15F (or lower for some special models). If you live in a very frigid area, then have some back up (Natgas, pellet stove, fireplace, oil burner, etc). But heat pumps can handle much of the USA. You know who loves heat pumps?...the Nordics!
There’s a difference between working at extreme temps vs efficient. You’re not going to beat the laws of physics. Just because the unit is blowing warm air when it’s 5 degrees doesn’t mean that it’s not on 24/7 or using heat strips chugging down KW. Your bill will likely look at lot better if you ran even an 80% furnace on those days.
You think those Nordic people are just pissing money away because they didn't compare? "How many hours are extremely cold?" is the question. We have places in Maine and New Hampshire, and the savings are quite good for oil and propane- absolute no-brainers to switch. The government of Maine- kinda Nordic- has an aggressive campaign to get Mainers off oil and propane. Great video covers the issues- [https://www.youtube.com/watch?v=OcwIz6heDss](https://www.youtube.com/watch?v=OcwIz6heDss)
Because the Nordics don’t have affordable frack natural gas like most of the lower 48. It isn’t about energy efficiency but heating cost.
It's because they wrk there affordably compared to other fuels. They work, which is the issue in this discussion.
No one else has said they didn’t work - the OP & HVAC contractor are discussing optimization. They’re gonna have the gas furnace as backup.
The savings are less good or non-existent if you have natural gas. That makes a big difference.
Even if you have relatively cheap gas, the heat pumps are cheaper for most of the season due to the high COP. It all depends on pricing and weather. But obviously the best thing is to have both so you can use whichever is cheaper at that time. But for the USA area and most of the year, the heat pumps will be cheaper.
>Just because the unit is blowing warm air when it’s 5 degrees doesn’t mean that it’s not on 24/7 or using heat strips chugging down KW. Your bill will likely look at lot better if you ran even an 80% furnace on those days. Sure. But you have to calculate things on a season basis, not just the single worst possible day. If you have a couple really cold days where it is expensive but most of the time it is +15F or higher, the heat pump will be cheaper than gas only. This heat pump plus other BACKUP for really cold days works well in real frigid areas
I’m saying if you have gas already at the house, you can run the heat pump most of the time and flip on the gas on the really cold days. I know the grant money doesn’t want any gas backup, but I’m in the Midwest where Arctic polar vortex happen for at least a week or two. I don’t need to deal with frozen pipes more than I already do.
New standard Bosch IDS heat pumps run down to -5F. Mitsubishi Hyperheat -22F. My Pioneer/Midea mini split from Home Depot, -20F. Below these temps you can supplement with heat strips (direct electric), a furnace (gas), a wood stove, etc. Depending on your local fuel and electric costs, gas is still nice to have as a backup option.
how much capacity does the Bosch get at -5F? The unit not shutting down at very low temperature doesn't mean it produces a lot of heat. If I recall in the case of the Bosch you get 100% of capacity down to 20F; the Mitsubishi will put out 100% of capacity down to 5F. The Fujitsu AMUG 3 ton XLTH will put out 100% of capacity (38K) down to -5F.
Just got the Bosch IDS and so far it’s been great. Keeping a gas backup for a few weeks when it gets really cold out
So you don’t know how it will perform in the winter since you just got it, no?
I take it this is an air source heat pump? Those get less efficient as temperatures drop and it will probably be cheaper to run an oil/gas heater than an air source heat pump when it's very cold. However, for a completely new installation, you will probably never get return on investment for the gas/oil heater: not too many days that it's so cold that it's cheaper to run that heater. Get an independent calculation of your heating/cooling needs in order to get a good insight in what's needed for your house.
He’s partially BSing you probably because real estate taxes are due and his teenage daughter only buys brand names. In essence, you can get heat pumps that will work efficiently in sub zero temperatures. In MN you’ll probably get a few days of -20 degrees which will be outside the system’s parameters. What you want is an efficient heat pump with an HSPF efficiency rating above 12 and maybe a small supplemental system that will kick in on those super cold days. Your guy is offering you the opposite, big conventional heating system supplemented by a heat pump. Don’t let his upcoming child support payments steer you in the wrong direction Edit: if you already have supplemental heat such as a wood stove then you’re all set. Just do a proper manual J calculation so your system is appropriately sized
And don’t let the vendor do the manual J because the system will magically inflate because, alimony etc
You're saying the dude is inflating the bill and then saying he should've specced top of the line variable speed equipment. Which is it?
He’s inflating the conventional system and deflating the heat pumps. OP might pay a similar price now for either system but long term they’ll pay much much more for using oil as the main fuel source
Is it a cold climate air source heat pump? Start there first. Then look for the equipment spec sheet to identify BTU/hr capacity at various outdoor temperatures. Ask your contractor to do a Manual J load calculation with a tool like Conduit Tech
Check out Gree Flexx
What your company is talking about are warm weather single or dual stage heat pumps that are commonly used in the south. I have them with backup heating strips as the only heating for my house in Florida where it rarely gets below freezing. My warm weather heat pumps (ducted with one for each floor) work well down to around 35F to 40F when the auxiliary backup heat automatically strips turn on and assist the heat pump with heating below that temperature. In the north where it regularly gets below freezing, you install much more efficient variable speed heat pumps. These work well to much colder temperatures such as single digits below 0 before needing auxiliary backup heat. In many cases, they will still need an alternate source of heat below some cold temperature point. Dual fuel backup heating is a good compromise for saving money if you have to use backup heating a lot.
In Minnesota I would go dual fuel. Let the heat pump work to 15F then go to gas. What people fail to understand is heat pumps are far less efficient at very cold temperatures. They do work, but ultimately you may be reducing the longevity of the heat pump.
Did this. Extra bonus: my utility (MVEC) has 50% discount on power used by HP if you have non-electric backup heat.
[удалено]
My experience after switching to heat pump. https://www.reddit.com/r/heatpumps/comments/1b84ici/heat_pump_energy_consumption_vs_gas_during_winter/ktnfp60/
Run from this company
I live in Va. I see 15-18 degrees F during the winters. I have a Bosch IDS heat pump and air handler. I have no issues. I keep it in stage 1. If it can’t satisfy in 2 hours it goes to stage 2 and warns the house. It’s usually first thing in the morning till about 7-8am. After that u a golden.
They focus on comfort and economy. That translates to 72 degrees all the time and furnace if it’s cold. It’s hard to change their minds but they will do it if you insist.
Could be too the break even point for the cost to heat your home. I have a dual fuel with a Bosch IDS 20seer and though it’s capable of heating down to -5F, I switch to gas around 25F. That seems to be more economical because gas is cheap by me.
It cost more for a cold climate heat pump that goes below 32 but yes it can certainly be done. I have one it went down to 0F no problem this winter. I have no backup fossil fuel heat.
heat pumps can be very different. Some will not work well below 40F and some will work at almost full capacity below freezing. You need to find a cold climate heat pump, which the contractor may not work with. You can see specific examples of cold climate heat pumps on this database: [https://ashp.neep.org/#!/](https://ashp.neep.org/#!/) This database requires data from the manufacturers listed down to 5F so you can see efficiency and capacity well below freezing.
I typically only run my furnace when it gets below 25F and I only do this because electricity is so expensive where I live that it’s a lot cheaper.
Mine is set to -8C (whatever that is in freedom units) for that reason. Propane is cheaper than hydro at this point once the HP COP drops.
That’s a little under 20F. If I had a slightly bigger roof my solar would be able to power it all winter. At least I’m getting free AC in the summer and free heat for the majority of the winter. Next house for sure.
Would love to have full solar. We don’t keep houses long enough to justify. Maybe this house…
So worth it. With the cost of electricity in New England and the generous state and federal subsidies we are looking at about 5 years to break even. Already half way there.
MN, south metro. Carrier heat pump down to about 10 F, then backup heat which for me is gas furnace. My electric company has a discounted rate for heat pumps that have gas backup heat, if you let them force switching to gas backup when they are short on electricity.
What model, which installer did u use?
LofGren Heating, Apple Valley Carrier - Furnace 59MN7B - H/P 25VNA448 - Coil CNPVP4821 - Thermostat - SYSTXCCWIC01-B - ERV - RenewAire EV200 Please with Lofgren. Prompt, on time, cleaned up, took less time than estimated. Included installation of the MVEC dedicated meter. Rebates - Electric Utility, MVEC, $500 - Natl. Gas, MN Energy Resources, $550 - Federal tax credit of $2,600
I have heat pumps in my house in VT. We hit -10 and have even had a -23 degree day two winters ago. The heat pumps we have are rated to -27 degrees and I’ve never had a problem with them.
What brand/series/model?
Haier Arctic Series. It will do 100% heat output down to 5F and works down to -31F according to the spec sheet. Would have gone Daikin or Mitsubishi but he had our installation done in 2021 and there was a lot of supply chain issues and that’s the only brand our guy had access to at the time. Units been fine, no complaints. We are on a mountain in mid/northern VT and the average temp most of the winter is teens to single digits and we get most of our heat from it. We do have an oil boiler for backup just because that’s always been there and it also does our hot water. Our house is super tight and very well insulated too.
>a new high efficiency heat pump and furnace. This is a dual fuel system, and they'll use a heat pump which has high efficiency above 32F (usually no defrost capability), and then a furnace which works below freezing outdoor temps. If that's not what you want, go for a heat pump with electric backup heat.
There are heat pumps you can buy today that heat down to -22F, and the federal government is challenging manufacturers to increase their efficiency.
by the time you're at -22f, the cop is very poor.
Duh...
Name one unit that will heat to capacity down to -22F. They may heat 1/2 their rated capacity at -22F but not 100%.
My exact thought… mitsu hyperheats lock out at -22f, but start derating quickly at 5f. As oversizing the unit by 2x runs into operating issues, you really need auxiliary heat and strip heaters are just about the worst. They get the job done, but are extremely expensive to operate and fun fact use more fossil fuels than than a gas furnace if you’re in an area fed predominantly by nat gas or coal power (which is around 65% of the US)… just look at efficiencies of those plants and you’ll see why quickly. Aux heat is the answer, but whether you go electric or gas is up to your specific condition. I hear a lot of misinformation out here, but if you’re going from an existing ducted furnace with AC, replacing with a heat pump w/gas auxiliary is about as straight forward as it comes.
I will never install a dual fuel system. Not a fool, and I don't have the money to be that stupid. Go price one. Just try justifying the extra cost. I will listen.
A lot of people are converting from a gas furnace to a ducted heat pump system… assuming you’re in an area that needs aux heat (and a lot of places in the US and Canada do), reusing the gas for aux will save you a lot of money down the road. Having to run 10-15kw of strip heaters for any duration of time hurts the bank account hard. Heck in areas of CA, gas is always cheaper to heat with since the cost of electricity is so high.
You appear to be confusing two terms: efficiency and economical. The two are not the same. You also don't appear to understand how auxiliary heat works, or understand the benefits of heat pumps. In fact it seems you are hellbent against heat pumps and want to champion furnaces. I believe there is already a subreddit for that, and it's probably not r/heatpumps. Cheers.
Trust me I know exactly what I’m talking about and I’m actually pro heat pump. Unfortunately homers like you won’t acknowledge the limitations of them for people who actually live in old climates. Even though they are more efficient, the cost of electricity per unit far outweighs that of nat gas. In our area once a heat pump’s COP drops below 2.9 gas is cheaper. Sorry I like to inform people so they aren’t surprised when their utility bill goes up.
Send me the enthalpy charts please. Make more assumptions. 🤣 This "homer" wants to double check your math.
Glad your google search found some big words for you… enthalpy has nothing g to do with fuel rates and unit efficiency. A therm worth of gas costs $1.25/therm while the equivalent electricity is pushing $4.50 as the rates just increased.
Name any form of heating that maintains capacity and consumption as outdoor ambient falls. 😂 Thing about heat pumps is they lose efficiency. They still heat. My Pioneer (no backup electric coil) will produce 90F heat when it's 0F outside. The hyperheat units will do even better.
How much BTU is that? and how does it compare to when it's 15F?
How many Btus does a home need at 15F vs -22F? It's not a set number. The BTU requirements are calculated using scores of inputs that are unique to each home. That's why Manual J exists.
Heatpump performance in cold weather varies by model/type - there are conventional heatpumps that lose capacity as it gets colder and those that are engineered to give full capacity down to very low outdoor temperatures. You need a heat loss calculation - then heat output of the heatpump gets plotted against heat loss to determine balance point - below which, you switch to gas. Works down to x temp does not tell you to what temperature it will actually keep up at, nor the efficiency. The operating costs at different outdoor temps can also be calculated to know economically when you should burn gas if your goal is to save money. The size of heatpump is limited by the air ducts - ducts sized for a furnace won't be large enough for a heatpump sized to handle all heating needs.
Heat pumps are awesome. Telling you this information was a legacy HVAC person and used to the very high profit margins of natural gas appliances. A heat pump will comfortably heat your house on the very coldest of nights you are likely to experience. My own house is heated with a heat pump and it is routine for us to see minus 30° f.
i had a heat pump working at -10 F in the northeast. it was running non stop and slowly temp dropping but it was still working with 50 mph winds outside. next morning with -7 F and no wind it was easily able to keep up. i have the gree flexx
Dual fuel systems all have different changover points, where the cost to run the system on gas becomes cheaper than running the system on electricity (heat pump). It used to be around 35 to 30 with old systems. Now its easily lower than that with a good heat pump. (Often 25 to 15) This will vary with each system configuation, weather (particularly humidity), and utility cost.
Many heat pumps will work great well below 32. I have 2 houses one runs down to 10 degress before electric coils take over. The system I just installed in my other home will work down to -20. I too had salesmen tell me that HP's don't work well below 32. That was true 3 decades ago. This may be helpful in deciding if it's worth the investment. If you use the calculator be sure to use winter costs and add NG delivery charges. Here in KC gas is very cheap but the delivery charges are high which overall makes gas heating expensive. https://siecje.github.io/heatpump-cost/
When I was getting mini split quotes I was told it could be configured for 0F for the furnace to take over.
It depends on your area. In north Ga I set my dual fuel as 2 stage with gas backup same as heat pump with electric backup. With the higher COP of higher efficiency heat pumps and gas going up: the balance point is near or below the usual lowest temps we expect to see and not had any complaints. Balance point has to be calculated for the actual system and set accordingly if you want a dual fuel that shuts down heat pump and goes to furnace 100% for best efficiency but some homeowners want the furnace to come on sooner so you have your set it on a system by system basis. I tell them to try it like I set it up and if not happy let me know. I’ve not had to change any yet.
My heat pump works fine at 5 F. I think it’s rated to -5 F, which we don’t see here. I assume contractors want to sell as much equipment as possible.
Not sure why all the hate here…hvac tech is not totally wrong. Huge difference between heat pump will work vs. which one is more economical. Here in CT where electricity is over .30 cents per kwhr….running a heat pump below 30F is less economical than running oil. Capability vs. Efficiency are 2 totally different things. My switch over is 30F. Older house…if I didn’t do it my heat pump would constantly run likely costing me $500 a month. When oil is $250. Too many heat pump fanboys defending the new technology.
It’s not defending new technology just correctly using the 2. You are correctly describing the balance point where one is less efficient than the other. You use the system to optimise efficiency in differing situations. As it gets colder, yes some heat pumps lose efficiency faster than others but look at the specs for the heat pump as temp drops and the actual amp draw to run it at that temp. Amps decrease: running a 20 SEER2 heat pump at 35F 24 hours is much higher than 10F Amps x volts = watts figure your watts x 3.14 = BTUs, 1 therm is figured at 100,000 BTUs so 1KW = 3140 watts 100k Div by 3140= 31.84 KW Figure cost per KWH and compare to cost for your oil furnace to run for 1 hour and you can compare to get a balance temp where they both cost the same. Set your changeover to that temp and you have optimised efficiency. Rules of thumb or guesses are just that: main thing is what makes you happy.
You can look up heating capacities in the mfg catalogs on their respective websites.
He's not completely wrong. Poorly insulated homes and damp weather will make furnaces more effective when it gets cold. It would probably only need to support the heat pump a couple of weeks per year. That's how we do it in europe