Will heat pumps replace gas heaters?

[stripedbass]

I have a direct-vent gas heater. It's a Vermont Castings model called Stardance ((broken link removed)).

However, recently fellow owners in my 12-unit condo building have started opting for heat pumps. They are both heaters and air conditioners. Is this the wave of the future? Are gas heaters such as my VC Stardance going to be obsolete?

Please see attached photos.

 

[peakbagger]

The short answer is yes. Heat pumps do not create heat they just move heat around. Even in cool weather they can be two to three hundred percent efficient. So for every BTU of electric power you put in them you get 2 to 3 btus of heat out. This works for both heating and cooling. Your stardance is always going to be less than 100%, probably 85 to 90%. Note heat pumps come in all sorts of configurations, the one in the photo is a ductless heat pump or frequently called a minisplit. There are other types of heat pumps that heat and cool air and pump it around in ductwork and they typically are far less efficient and switch to electric backup heat when the temps get near freezing. My assumption is that your association is looking at minisplits set up for cold weather heating. They are usually referred to as cold climate heat pumps or cold climate minisplits.

Mini splits are an electrical appliance much safer than a gas fired appliance, in theory home owners insurance might drop if all the units switch. There are trade offs, minisplits warm air and move it around with a fan. Most people have to run the heat higher than with a radiant source like a gas stove. There is no cuddling up around the minisplit . The other trade off is when you need the heat the most in very cold weather minisplit peformance starts to drop and eventually gets down to about what electric heat costs. In very cold climates they may shut off typically around minus 12F so probably not a worry in the Boston area. Boston doesnt really get a lot of super cold snaps and when the temps are in the 20s to 60s the heat pump is in its most efficient range so your bills are much lower which offsets the cold snaps

The temptation is to undersize them to reduce initial cost but without a backup for cold weather, a home owner could be surprised that they cannot heat their house. A few electric space heaters can help but that brings up another question, does the building and each apartment have a big enough electrical service to supply power to all the minisplits in really cold weather along with the inevitable space heaters?. Especially in cold weather, minisplits are not instant heat, they are best set and forget, unlike a gas heater that heats up quick and can be turned off. For people who set back their heat with other fuels, its going to be a learning curve with a minisplit. Note if you do not have AC or have window units, minisplits cool quite efficiently far more than window units and are much quieter.

The other big aspect is the actual cost of fuel. Most of the electricity in new england is coming from gas fired powerplants and due to the war in Europe and other regional factors, natural gas is going to be incredibly expensive this winter so electricity will also be incredibly expensive. It up to you to do the math in which fuel, gas or electricity is the least expensive this winter. Mass is committed to switching to renewable electricity, right now its in the 30% range with 35% the goal in 2030. Great idea but right now the subsidies being paid for renewables are being piled onto electric bills. This is not the issue with gas so even though it my be less efficient by far, cost wise it may be equal or less although both gas and electricity are both going to be very expensive this winter barring a big change in Europe.

The final thing is if the power goes out, your heat is gone until the power is back on, unless you have a very large generator, you probably can not run minisplit with it as it could draw too much power. With a gas stove, its highly unlikely the gas will be off when the electric power is off so you can still heat your house and maybe even heat up food to eat. If you are in an area with a lot of power outages its something to consider.

Mass pays out a rebate for installing these units and any dealer will have the details. They are best installed by pro and figure $4000 to $5000 installed cost for a 12,000 btu unit. Unless you have a very small condo you may need two or something called a multihead unit but the only way to be sure is for the dealer to do a manual J heat load calculation to make sure that you have enough heat in very cold weather. If the building has backup heat then I suggest a 12,000 btu unit but if the place is old and drafty you may need more.

 

[EbS-P]

In areas where it’s gets cold I would always want a heatpump and another heat source. I like my heatpump. Most houses here in the south that’s what we heat with. Many/most/all have resistive electric strips that function as the second heat source and provide comfort during defrost cycles.

Short answer is yes they are the future if you figure they have been used for decades. They are the most efficient solution for sure and now there are models that function decently in the cold to very cold you will see lots of them. And with solar they just can’t beat.

Case in point. https://www.hearth.com/talk/threads/mini-split-heating-at-8f.190789/

 

[Poindexter]

Good points here already.

1. Electrical capacity of the building's service.

2. Actual cost to run. I paid (all fees included) 29.95 cents per kilowatt hour last month for electricity. I bought cords and cords of spruce this spring at $350 each dropped in my driveway as green splits. My last electric bill was a different page than I used below; for the service period 06-02 to 07-05-2022 I had 413 kwh delivered to the house, my bill was $134, 32.44 cents per kwh last month.

So there is some work involved with the spruce. I bought green. I had to stack it, it is now seasoned, I still have to carry it to the stove and carry out the ash. But I bought 18 million BTUs (1 cord) of spruce for $350.

1 kwh = 3412 BTU. The cord of spruce represents 5275 kwh of energy. If I buy it at 29.95 cents per kwh, I would pay $1579 for one cord of spruce as electricity, or $350 for the same amount of energy as wood.

Even if a minisplit was 300% efficient at -30dF (it won't be), $350 x3 = $1,050; alternatively $1579 / 3= $526. Heating with wood is still about two thirds the price - because local to me electricity is expensive but wood is cheap.

I am looking at minisplits because I cannot cool the air in my home during summer months with either my oil fired boiler or my wood fired stove.

East of the Hudson river you got a lot of regulation to look at. Natural gas does burn clean, but it is still fossil carbon, and it is pricey right now. You are blessed with a mature enough grid that one powerplant going down can often be carried by the other plants on the grid, giving you more dependable electric service than I have. I have no idea if you could burn wood in your jurisdiction, or how much you would have to pay or how far away the wood would be shipped from.

I don't know what your local options are, but you are far enough north I doubt a minisplit can meet all of your year round heating needs. Given your NG is already installed I would look to see if there is a dramatically more efficient direct vent heater you could upgrade to - with low expectations.

The lastest generation of heat pump is impressive, but they do have limits.

 

[Poindexter]

You might look at propane, the vast majority of it sold in the US is produced in the US. It is provided at a different service pressure and a different density than NG. NO idea if it would work with a direct vent system even with the burner converted. To not wrestle your own tanks and have a truck come to top your tank off you will probably need at least a 200 gallon tank on the property which your HOA may not allow.

Kinda sucks your two primary heat sources are Natural Gas. Usually NG is a pretty good thing to have available, but when all your options go back to one fuel you don't have a lot of arrows in your quiver.

 

[stoveliker]

Good points here already.

1. Electrical capacity of the building's service.

2. Actual cost to run. I paid (all fees included) 29.95 cents per kilowatt hour last month for electricity. I bought cords and cords of spruce this spring at $350 each dropped in my driveway as green splits. My last electric bill was a different page than I used below; for the service period 06-02 to 07-05-2022 I had 413 kwh delivered to the house, my bill was $134, 32.44 cents per kwh last month.

So there is some work involved with the spruce. I bought green. I had to stack it, it is now seasoned, I still have to carry it to the stove and carry out the ash. But I bought 18 million BTUs (1 cord) of spruce for $350.

1 kwh = 3412 BTU. The cord of spruce represents 5275 kwh of energy. If I buy it at 29.95 cents per kwh, I would pay $1579 for one cord of spruce as electricity, or $350 for the same amount of energy as wood.

Even if a minisplit was 300% efficient at -30dF (it won't be), $350 x3 = $1,050; alternatively $1579 / 3= $526. Heating with wood is still about two thirds the price - because local to me electricity is expensive but wood is cheap.

I am looking at minisplits because I cannot cool the air in my home during summer months with either my oil fired boiler or my wood fired stove.

East of the Hudson river you got a lot of regulation to look at. Natural gas does burn clean, but it is still fossil carbon, and it is pricey right now. You are blessed with a mature enough grid that one powerplant going down can often be carried by the other plants on the grid, giving you more dependable electric service than I have. I have no idea if you could burn wood in your jurisdiction, or how much you would have to pay or how far away the wood would be shipped from.

I don't know what your local options are, but you are far enough north I doubt a minisplit can meet all of your year round heating needs. Given your NG is already installed I would look to see if there is a dramatically more efficient direct vent heater you could upgrade to - with low expectations.

The lastest generation of heat pump is impressive, but they do have limits.

I think a cold climate minisplit can do enough in Boston. And wood heat in an apartment building is unlikely to happen (be approved).

 

[EbS-P]

I think a cold climate minisplit can do enough in Boston. And wood heat in an apartment building is unlikely to happen (be approved).

And if you have gas for the coldest 14 days a year it seems like a great solution.

 

[Highbeam]

There is no limit really. Just put in more, or a larger, heat pump until your winter needs are satisfied. These things make less heat when it’s cold out but at a known level so simply buy what you need.

I just installed one to heat my whole 1963 home and it’s currently cooling the whole home at 96 degrees outdoor temps. It’s sized to heat the whole place at 5 degrees per the manufacturer’s output chart.

Don’t worry about oversizing. They modulate way down and even can cycle like traditional equipment.

 

[stripedbass]

The short answer is yes. Heat pumps do not create heat they just move heat around. Even in cool weather they can be two to three hundred percent efficient. So for every BTU of electric power you put in them you get 2 to 3 btus of heat out. This works for both heating and cooling. Your stardance is always going to be less than 100%, probably 85 to 90%. Note heat pumps come in all sorts of configurations, the one in the photo is a ductless heat pump or frequently called a minisplit. There are other types of heat pumps that heat and cool air and pump it around in ductwork and they typically are far less efficient and switch to electric backup heat when the temps get near freezing. My assumption is that your association is looking at minisplits set up for cold weather heating. They are usually referred to as cold climate heat pumps or cold climate minisplits.

Mini splits are an electrical appliance much safer than a gas fired appliance, in theory home owners insurance might drop if all the units switch. There are trade offs, minisplits warm air and move it around with a fan. Most people have to run the heat higher than with a radiant source like a gas stove. There is no cuddling up around the minisplit . The other trade off is when you need the heat the most in very cold weather minisplit peformance starts to drop and eventually gets down to about what electric heat costs. In very cold climates they may shut off typically around minus 12F so probably not a worry in the Boston area. Boston doesnt really get a lot of super cold snaps and when the temps are in the 20s to 60s the heat pump is in its most efficient range so your bills are much lower which offsets the cold snaps

The temptation is to undersize them to reduce initial cost but without a backup for cold weather, a home owner could be surprised that they cannot heat their house. A few electric space heaters can help but that brings up another question, does the building and each apartment have a big enough electrical service to supply power to all the minisplits in really cold weather along with the inevitable space heaters?. Especially in cold weather, minisplits are not instant heat, they are best set and forget, unlike a gas heater that heats up quick and can be turned off. For people who set back their heat with other fuels, its going to be a learning curve with a minisplit. Note if you do not have AC or have window units, minisplits cool quite efficiently far more than window units and are much quieter.

The other big aspect is the actual cost of fuel. Most of the electricity in new england is coming from gas fired powerplants and due to the war in Europe and other regional factors, natural gas is going to be incredibly expensive this winter so electricity will also be incredibly expensive. It up to you to do the math in which fuel, gas or electricity is the least expensive this winter. Mass is committed to switching to renewable electricity, right now its in the 30% range with 35% the goal in 2030. Great idea but right now the subsidies being paid for renewables are being piled onto electric bills. This is not the issue with gas so even though it my be less efficient by far, cost wise it may be equal or less although both gas and electricity are both going to be very expensive this winter barring a big change in Europe.

The final thing is if the power goes out, your heat is gone until the power is back on, unless you have a very large generator, you probably can not run minisplit with it as it could draw too much power. With a gas stove, its highly unlikely the gas will be off when the electric power is off so you can still heat your house and maybe even heat up food to eat. If you are in an area with a lot of power outages its something to consider.

Mass pays out a rebate for installing these units and any dealer will have the details. They are best installed by pro and figure $4000 to $5000 installed cost for a 12,000 btu unit. Unless you have a very small condo you may need two or something called a multihead unit but the only way to be sure is for the dealer to do a manual J heat load calculation to make sure that you have enough heat in very cold weather. If the building has backup heat then I suggest a 12,000 btu unit but if the place is old and drafty you may need more.

Peakbagger,

Thanks for the detailed feedback.

My Vermont Castings Stardance is quite old. And it needs some work.

I'm just wondering whether I should get a newer Stardance or other similar heater. Or should I simply switch over to a heat pump? My condo is only about 600 square feet.

I'm still digesting your post. It has a lot in it. Thanks!

 

[stripedbass]

In areas where it’s gets cold I would always want a heatpump and another heat source. I like my heatpump. Most houses here in the south that’s what we heat with. Many/most/all have resistive electric strips that function as the second heat source and provide comfort during defrost cycles.

Short answer is yes they are the future if you figure they have been used for decades. They are the most efficient solution for sure and now there are models that function decently in the cold to very cold you will see lots of them. And with solar they just can’t beat.

Case in point. https://www.hearth.com/talk/threads/mini-split-heating-at-8f.190789/

EbS-P,

Thanks for your response. For me, heat pumps are a totally new thing. Do you like their cooling capability?

 

[stripedbass]

Good points here already.

1. Electrical capacity of the building's service.

2. Actual cost to run. I paid (all fees included) 29.95 cents per kilowatt hour last month for electricity. I bought cords and cords of spruce this spring at $350 each dropped in my driveway as green splits. My last electric bill was a different page than I used below; for the service period 06-02 to 07-05-2022 I had 413 kwh delivered to the house, my bill was $134, 32.44 cents per kwh last month.

So there is some work involved with the spruce. I bought green. I had to stack it, it is now seasoned, I still have to carry it to the stove and carry out the ash. But I bought 18 million BTUs (1 cord) of spruce for $350.

1 kwh = 3412 BTU. The cord of spruce represents 5275 kwh of energy. If I buy it at 29.95 cents per kwh, I would pay $1579 for one cord of spruce as electricity, or $350 for the same amount of energy as wood.

Even if a minisplit was 300% efficient at -30dF (it won't be), $350 x3 = $1,050; alternatively $1579 / 3= $526. Heating with wood is still about two thirds the price - because local to me electricity is expensive but wood is cheap.

I am looking at minisplits because I cannot cool the air in my home during summer months with either my oil fired boiler or my wood fired stove.

East of the Hudson river you got a lot of regulation to look at. Natural gas does burn clean, but it is still fossil carbon, and it is pricey right now. You are blessed with a mature enough grid that one powerplant going down can often be carried by the other plants on the grid, giving you more dependable electric service than I have. I have no idea if you could burn wood in your jurisdiction, or how much you would have to pay or how far away the wood would be shipped from.

I don't know what your local options are, but you are far enough north I doubt a minisplit can meet all of your year round heating needs. Given your NG is already installed I would look to see if there is a dramatically more efficient direct vent heater you could upgrade to - with low expectations.

The lastest generation of heat pump is impressive, but they do have limits.

Poindexter,

The electrical capacity of our condo building is a huge ongoing issue.

Anyway, one of the things I'm going to do is look to see whether there's a much more efficient direct vent heater I can get. My current one is quite old and needs some work. I'm at the very early stages right now. One great thing about a heat pump is being able to cool the air in the summer. I'm not a big fan for window air conditioners.

Thanks for your feedback.

 

[stripedbass]

There is no limit really. Just put in more, or a larger, heat pump until your winter needs are satisfied. These things make less heat when it’s cold out but at a known level so simply buy what you need.

I just installed one to heat my whole 1963 home and it’s currently cooling the whole home at 96 degrees outdoor temps. It’s sized to heat the whole place at 5 degrees per the manufacturer’s output chart.

Don’t worry about oversizing. They modulate way down and even can cycle like traditional equipment.

Highbeam,

I like your sunny outlook. Hope it rubs off on me.

 

[stoveliker]

I bought a minisplit for cooling and are using it to heat as well because I have enough solar kWhs.

Yes they are very good for cooling. More quiet than the ducted system I had in the South and more quiet than the window units folks have on LI. Both the inside and outside units! And more efficient too than both.

 

[Jerkzack]

I'll also chime in and say yes.

We installed a 4 ton Bosch ducted heat pump last Sept. It is set up similar to a furnace, air handler or blower or heat exchanger in the basement and the heat pump/compressor installed outdoors.
It has heated and cooled our 2500sq ft house quite well this past year. The only back up we currently have is the electric grid in the air handler. This is currently not sufficient if the power goes out, so I'm adding a wood insert to a current fireplace and also considering adding a wood furnace in the basement in case we lose power for more than a few hours. I have access to a decent amount of free or almost free wood, so it's peace of mind for me. Plus I'm cheap and would like to see a cheaper power bill. But wood will never be our main source of heat. At least in the near future.

In NB, Canada, we have some of the cheapest electricity going at around $0.11/kwh. Other provinces have big incentives for renewable energy, so it's only a matter of time until we start seeing more renewable energy here, which in turn will only make HP's cheaper and cheaper to operate.

Plus zero work, aside from the odd maintenance/cleaning of the compressor and a filter change every 90 days. Much less costly to maintain than an oil or gas furnace. And much less manual labor than wood heat.

 

[EbS-P]

There is no limit really. Just put in more, or a larger, heat pump until your winter needs are satisfied. These things make less heat when it’s cold out but at a known level so simply buy what you need.

I just installed one to heat my whole 1963 home and it’s currently cooling the whole home at 96 degrees outdoor temps. It’s sized to heat the whole place at 5 degrees per the manufacturer’s output chart.

Don’t worry about oversizing. They modulate way down and even can cycle like traditional equipment.

I’ve tried going by design temp charts is fine but even the 99% leaves 4 days every statically year that you are under sized. Any deviation from from the mean only increases means more days where your system is under sized. The variable speed compressor is a huge leap forward and makes correct sizing almost childishly easy but in colder climates where delta T during the winter is 3-4 times greater than in the summer you really are pushing turn down limits (not being able to go low enough) on larger systems during the summer. And the counter point is we just install multiple units. Which can be done. My AC runs constantly from 2-3 pm to 11 pm on the hot sunny days here. Which means it’s heating capacity is woefully under powered. Hence the wood stoves. But it does ok in the summer. Delta T of 20 degrees or less. That’s only a 45 degree winter temp. Direct solar game probably takes that number down to 35-40. My 99% design temp is 28dF here in the south.

 

[EbS-P]

EbS-P,

Thanks for your response. For me, heat pumps are a totally new thing. Do you like their cooling capability?

I sweat like a pig. I gotta have my AC. Just told my in laws in Maine last week that I’m not visiting again unless they install a heatpump/AC. Living room was 88 and I was packing and hauling all our stuff.

Mine is a (36k btu) 3 ton unit for 3000 sq ft in the south. It’s undersized but a third is basement so we get by and can almost always get back down to 78 by 9 pm. Many many homes have heatpump / ACs down here. It’s not new tech down here. Most units have 10 kw restive heat trips in them for back up heat or when the unit goes into defrost mode. That’s when it runs in AC mode to melt ice off the outside coil. The mini splits just turn the indoor blower down but still might blow some cold air. Others with more experience can chime in as to if this is really noticeable. I Can tell you that mine were not working for the first 4 years we lived here and one cold snap I just had to turn the heatpump off as it was blowing more cold air than hot.

600 sq ft isn’t big. Are you and end unit? I’d upsize by by some amount (3k btus is the smallest step size I think) if that’s the case. Your back up heat could just be two space heaters. Not efficient but effective and not needed very often. Or just buy big and be warm (till the power goes out)

 

[Highbeam]

Just buy big and be warm (until the power goes out). Really thats what I’m saying too. Oversize. The equipment can modulate and then cycle on and off if it’s hugely oversized.

Anything with backup resistance heat is old school technology. This is something new. Look into it. Full rated output at 17 below zero? Some can do that.

 

[EbS-P]

Just buy big and be warm (until the power goes out). Really thats what I’m saying too. Oversize. The equipment can modulate and then cycle on and off if it’s hugely oversized.

Anything with backup resistance heat is old school technology. This is something new. Look into it. Full rated output at 17 below zero? Some can do that.

Old school is still in down here. Trane has not improved their package units in about 12-15 years