Thanks- as a researcher I do try to present all sides of the story and let the reader make the decision for him/her self. Heat pumps can be a great technology, if it's the right fit.
I love the fact you captured fuel cost in your article. I ran the numbers for my 96% gas furnace vs a 400% heat pump. Based on my gas cost vs my electric rate it's still cheaper to run the gas furnace. We all know that 400% only happens in the lab.
If you really want to embrace heat pumps, a duel fuel system is always an option. They run on heat pump during mild weather, then switch to gas furnace when the weather cools. The advantage is you can size the heat pump for cooling load.
“I agree that hybrid solutions are generally a good option based on sound physics.”…..It’s fascinating that I’ve seen virtually this exact sentence applied to automobiles as well from the likes of Doomberg and others. Why do we have to live with dogmatic edicts instead?
The heat pump issue is akin to the EV conundrum, the claimed result and cost are subjected to ideally conditions at every LEVEL. The infrastructure, grid, regulations, subsidies, adoption, supply, demand, labor, and WEATHER all must coordinate at a rate and level never before seen or could occur.
I’m always a little “new technology averse” since new companies may go out of business, leaving you with no place to buy parts and having to buy a completely new one. That happened to me with tankless water heater. Assuming your local folks know how to install them; just talking about “cold weather” pumps here. There’s a great deal more to new technologies than generalized proclamations that they are better.
I have a ground source heat pump (geothermal) forced air system. Big expensive and adequate for 10 months a year, fantastic for air conditioning, but when the winter cold (-15 to -25) sets in its a struggle to stay comfortable. It creates 100 degree air (versus 120 for natural gas) at the vents so it FEELS like cold air blowing. So to stay comfortable during the cold snaps you drag out electric heaters. And NO there is nothing wrong with the system, it has properly designed, engineered and installed properly. It’s just the way it is, otherwise known as physics. As far the economics go the extra cost of such a system will very likely never be offset by savings on energy costs.
Wow, thanks for your story -- sorry to hear that even such an expensive heat pump can't provide adequate heat when it's most needed. And I agree, any added efficiency is likely offset by the need to use electric space heaters, which are generally energy hogs.
People who have never passed a basic physics class, and maybe a little bit of engineering, need to stay completely out of any and all discussions involving energy production and use.
Regarding homes in the milder climate of CA: some don’t have ducting, instead relying on a single space heater type furnace that usually sits in the wall close to the center of the home for warmth in winter and fans or window-mounted air conditioning units in summer.
Honestly at my old home in San Diego, we seldom turned on our gas furnace and didn’t have air conditioning. I grew up in a cold climate though and was never phased by the cooler temperatures in Southern Coastal California winters though. The number of times the thermometer broke 30C that close to the coast in summer could be counted on two hands. Fans worked incredibly well along with open windows to make things feel a bit cooler. Inland by even a few miles though and the extremes on both ends of the thermometer increase.
CA’s heat pump mandates are also insane. Take a look at San Diego’s Climate Action Plan.
I think heat pumps for CA apply more in the SoCal mountains/desert and in northern parts of the state where it can get quite cold in the winters. Coastal communities are very lucky and barely need either heat or AC!
I'm a bit dubious about your price delta between inverter driven and non-inverter-driven heat pumps. Or at least how much of that represents a real durable difference due to technology cost rather than a short term premium for a product that is relatively new to the US market.
Firstly because most of the total cost is due to system costs and installation costs rather than the unit equipment cost and the former categories should be the same for either. Especially for older properties, the real cost difference (including capital and fuel costs) is going to be driven by these system costs rather than the cost difference between the boiler / heat pump. Typically whether you've got a ducted system or hydronic / radiator system the existing system will have been sized for high flow temperatures and this either kills your system efficiency (if you run a heat pump at high output temperatures) or requires expensive and disruptive ducting / radiator upgrades (if you want to run at high system efficiency).
Second because the power electronics and motor price difference are pretty small so you'd expect a convergence over time in the price delta to reflect that.
Third because the US is the only remaining major market where non-inverter ACs are not a small majority of new sales and therefore we're pretty far down the learning rate curve for inverter driven technology. I'm not sure why this is, although I suspect that the preference for central ducted systems vs mini-splits has a lot to do with it since the benefits are not quite as great in the former as they are in the latter. It's also the case that in other motor applications of various sizes, inverter driven pumps have been gaining market share very consistently and are now often the default option.
Finally on the electricity-dependent heating point, I'm not sure how different this is in practice from how people have their existing natural gas / oil systems configured. In theory the main energy input isn't electrical so you needn't freeze during an electricity outage, in practice these systems have electrically driven fans, pumps, etc. and don't actually work when there's no electricity. Individual users in areas with unreliable electricity may well decide that they want generator / battery backup to power the control systems and electrical components of their gas or oil heating system but most people aren't currently doing that and switching to a heating system which gets all of its energy from electricity wouldn't increase their risk exposure.
Thanks for your input! On the issue of mini-splits, I think these are becoming more common in smaller and older homes without existing ducting, but as you pointed out, there's limited data about their actual efficiency. I'm following this issue closely and hope to write further articles that capture more recent and relevant information and consider various dimensions like climate zones, building vintage, etc.
Thanks for this post. You made a good point about the cost of the most efficient and sophisticated ASHPs out there. We purchased a cold-climate ASHP and it wasn’t cheap even after the utility rebates and tax credits. It’s also true that it’s not as environmentally friendly as advertised if the electricity used to power it comes primarily from coal powered plants. I do have a few observations to share with you about the cold-climate ASHP we installed in our Twin Cities home.
1) The variable speed unit we have is very quiet and keeps the temperature of our house in a more consistent range than any forced-air gas furnace we have owned ever did.
2) The ASHP works in tandem with our forced air gas furnace. We set the lock-out at +15F so only the furnace runs below that temperature. That’s more economical for us since as you explained the efficiency of the ASHP drops off the colder it gets outside.
3) Costs for electricity here is about 14 cents/kWh, but we are on a load management program so we are charged only 7-8 cents/kWh for electricity used to run the ASHP. That’s quite a savings.
4) Our energy costs during the winter for our system are higher than if we just used a 95% efficient forced-air gas furnace, but not outrageously so. I would put it at $1.00 to $3.00 more per day depending on the weather. Sure, it will add up, but saving money was not our goal when we had our system installed.
5) Finally, will an ASHP always be more expensive to run than a gas furnace? What if gas prices rise dramatically over time. The expense of running the furnace is nearly all due to the cost of natural gas (and a pittance for electricity to run the blower.) The cost of electricity may not rise as quickly if the electricity is produced by a mix of coal, gas, wind, solar, hydro, etc. I don’t know, that’s above my pay grade to figure out.
So, we are happy with our ASHP, but they are not for everyone. You should look carefully at your individual situation (climate, type of house, cost of electricity and gas, etc) before purchasing one.
If natural gas prices rise, electric prices will follow. More than 50% of our power is fueld by natural gas and is unlikely to change for the foreseeable future.
I agree. My question though is whether the cost to heat a home will rise faster if heated solely with natural gas versus a home heated with a heat pump. If natural gas prices increase, the effect on cost may be greater with the furnace because it relies solely on natural gas whereas natural gas is only part of the energy mix that supplies electricity to the heat pump. I only posed that question because I believe K.T. remarked that a downside of heat pumps is that as electricity prices increase, the cost of operating a heat pump may dramatically increase. I’m wondering whether the cost to operate a natural gas furnace might exceed that of a heat pump down the road. To be honest, this question is really getting into the weeds and is probably trivial when discussing the pros and cons of heat pumps.
Gotcha, the reality is without a strong move to nuclear that slow rise in electricity prices unlikely. Commercial wind and solar are actually pretty expensive energy sources even with the claimed free fuel. The fact they can only run 25% to 35% of the time, and that run time is up to nature makes them an undependable source. They usually have to have gas generation in reserve to cover them and that is expensive .
The most informative piece that I’ve read on heat pumps! (I’ve read a bunch)
You were successful in maintaining your objectivity on a topic in which most authors are obviously “pitching” a pro or con opinion.
Thanks- as a researcher I do try to present all sides of the story and let the reader make the decision for him/her self. Heat pumps can be a great technology, if it's the right fit.
I love the fact you captured fuel cost in your article. I ran the numbers for my 96% gas furnace vs a 400% heat pump. Based on my gas cost vs my electric rate it's still cheaper to run the gas furnace. We all know that 400% only happens in the lab.
If you really want to embrace heat pumps, a duel fuel system is always an option. They run on heat pump during mild weather, then switch to gas furnace when the weather cools. The advantage is you can size the heat pump for cooling load.
Thanks for your comment -- that is an eye-opening observation! I agree that hybrid solutions are generally a good option based on sound physics.
“I agree that hybrid solutions are generally a good option based on sound physics.”…..It’s fascinating that I’ve seen virtually this exact sentence applied to automobiles as well from the likes of Doomberg and others. Why do we have to live with dogmatic edicts instead?
Because most policymakers have never been required to take a science class, let alone an engineering course.
The heat pump issue is akin to the EV conundrum, the claimed result and cost are subjected to ideally conditions at every LEVEL. The infrastructure, grid, regulations, subsidies, adoption, supply, demand, labor, and WEATHER all must coordinate at a rate and level never before seen or could occur.
Very good point. This is why it is important to take any model-based impact analysis with a whole lot of salt.
I’m always a little “new technology averse” since new companies may go out of business, leaving you with no place to buy parts and having to buy a completely new one. That happened to me with tankless water heater. Assuming your local folks know how to install them; just talking about “cold weather” pumps here. There’s a great deal more to new technologies than generalized proclamations that they are better.
That's a great point about new tech companies going out of business. Thanks for your comment!
I have a ground source heat pump (geothermal) forced air system. Big expensive and adequate for 10 months a year, fantastic for air conditioning, but when the winter cold (-15 to -25) sets in its a struggle to stay comfortable. It creates 100 degree air (versus 120 for natural gas) at the vents so it FEELS like cold air blowing. So to stay comfortable during the cold snaps you drag out electric heaters. And NO there is nothing wrong with the system, it has properly designed, engineered and installed properly. It’s just the way it is, otherwise known as physics. As far the economics go the extra cost of such a system will very likely never be offset by savings on energy costs.
Wow, thanks for your story -- sorry to hear that even such an expensive heat pump can't provide adequate heat when it's most needed. And I agree, any added efficiency is likely offset by the need to use electric space heaters, which are generally energy hogs.
People who have never passed a basic physics class, and maybe a little bit of engineering, need to stay completely out of any and all discussions involving energy production and use.
COMPLETELY.
HAHAHA! Couldn't agree more. Just trying to separate the wheat from the chaff.
Great piece!
👍 👌 teaching article, and a must read with fun puns and humor.
Q: do I have any tax dollars left for heat pump subsidies ? 🤔
Regarding homes in the milder climate of CA: some don’t have ducting, instead relying on a single space heater type furnace that usually sits in the wall close to the center of the home for warmth in winter and fans or window-mounted air conditioning units in summer.
Honestly at my old home in San Diego, we seldom turned on our gas furnace and didn’t have air conditioning. I grew up in a cold climate though and was never phased by the cooler temperatures in Southern Coastal California winters though. The number of times the thermometer broke 30C that close to the coast in summer could be counted on two hands. Fans worked incredibly well along with open windows to make things feel a bit cooler. Inland by even a few miles though and the extremes on both ends of the thermometer increase.
CA’s heat pump mandates are also insane. Take a look at San Diego’s Climate Action Plan.
https://www.greenleapforward.wtf/p/americas-finest-magical-thinking?utm_source=publication-search
SD's plan is completely bonkers!
I think heat pumps for CA apply more in the SoCal mountains/desert and in northern parts of the state where it can get quite cold in the winters. Coastal communities are very lucky and barely need either heat or AC!
I'm a bit dubious about your price delta between inverter driven and non-inverter-driven heat pumps. Or at least how much of that represents a real durable difference due to technology cost rather than a short term premium for a product that is relatively new to the US market.
Firstly because most of the total cost is due to system costs and installation costs rather than the unit equipment cost and the former categories should be the same for either. Especially for older properties, the real cost difference (including capital and fuel costs) is going to be driven by these system costs rather than the cost difference between the boiler / heat pump. Typically whether you've got a ducted system or hydronic / radiator system the existing system will have been sized for high flow temperatures and this either kills your system efficiency (if you run a heat pump at high output temperatures) or requires expensive and disruptive ducting / radiator upgrades (if you want to run at high system efficiency).
Second because the power electronics and motor price difference are pretty small so you'd expect a convergence over time in the price delta to reflect that.
Third because the US is the only remaining major market where non-inverter ACs are not a small majority of new sales and therefore we're pretty far down the learning rate curve for inverter driven technology. I'm not sure why this is, although I suspect that the preference for central ducted systems vs mini-splits has a lot to do with it since the benefits are not quite as great in the former as they are in the latter. It's also the case that in other motor applications of various sizes, inverter driven pumps have been gaining market share very consistently and are now often the default option.
Finally on the electricity-dependent heating point, I'm not sure how different this is in practice from how people have their existing natural gas / oil systems configured. In theory the main energy input isn't electrical so you needn't freeze during an electricity outage, in practice these systems have electrically driven fans, pumps, etc. and don't actually work when there's no electricity. Individual users in areas with unreliable electricity may well decide that they want generator / battery backup to power the control systems and electrical components of their gas or oil heating system but most people aren't currently doing that and switching to a heating system which gets all of its energy from electricity wouldn't increase their risk exposure.
Thanks for your input! On the issue of mini-splits, I think these are becoming more common in smaller and older homes without existing ducting, but as you pointed out, there's limited data about their actual efficiency. I'm following this issue closely and hope to write further articles that capture more recent and relevant information and consider various dimensions like climate zones, building vintage, etc.
COP is the heat pump parameter.
An AC moves heat from inside to out.
A heat pump moves heat from outside to in.
https://learnmetrics.com/coefficient-of-performance/#:~:text=Here%E2%80%99s%20how%20you%20can%20calculate
Nothing is 300% efficient.
Moving energy from cold to hot requires work no matter the direction.
energy from plug + energy from cold = energy to hot
One direction it's AC, other direction it's heat.
The colder the cold the more kW to deliver the needed hot.
That's why below 40 F it becomes all plug.
Burning NG at point of use i.e. water, air, food, loses about 15% of its energy.
Converting NG to electricity loses about 65% before it even leaves the plant site.
Really^3 dumb!
Thanks for this post. You made a good point about the cost of the most efficient and sophisticated ASHPs out there. We purchased a cold-climate ASHP and it wasn’t cheap even after the utility rebates and tax credits. It’s also true that it’s not as environmentally friendly as advertised if the electricity used to power it comes primarily from coal powered plants. I do have a few observations to share with you about the cold-climate ASHP we installed in our Twin Cities home.
1) The variable speed unit we have is very quiet and keeps the temperature of our house in a more consistent range than any forced-air gas furnace we have owned ever did.
2) The ASHP works in tandem with our forced air gas furnace. We set the lock-out at +15F so only the furnace runs below that temperature. That’s more economical for us since as you explained the efficiency of the ASHP drops off the colder it gets outside.
3) Costs for electricity here is about 14 cents/kWh, but we are on a load management program so we are charged only 7-8 cents/kWh for electricity used to run the ASHP. That’s quite a savings.
4) Our energy costs during the winter for our system are higher than if we just used a 95% efficient forced-air gas furnace, but not outrageously so. I would put it at $1.00 to $3.00 more per day depending on the weather. Sure, it will add up, but saving money was not our goal when we had our system installed.
5) Finally, will an ASHP always be more expensive to run than a gas furnace? What if gas prices rise dramatically over time. The expense of running the furnace is nearly all due to the cost of natural gas (and a pittance for electricity to run the blower.) The cost of electricity may not rise as quickly if the electricity is produced by a mix of coal, gas, wind, solar, hydro, etc. I don’t know, that’s above my pay grade to figure out.
So, we are happy with our ASHP, but they are not for everyone. You should look carefully at your individual situation (climate, type of house, cost of electricity and gas, etc) before purchasing one.
If natural gas prices rise, electric prices will follow. More than 50% of our power is fueld by natural gas and is unlikely to change for the foreseeable future.
I agree. My question though is whether the cost to heat a home will rise faster if heated solely with natural gas versus a home heated with a heat pump. If natural gas prices increase, the effect on cost may be greater with the furnace because it relies solely on natural gas whereas natural gas is only part of the energy mix that supplies electricity to the heat pump. I only posed that question because I believe K.T. remarked that a downside of heat pumps is that as electricity prices increase, the cost of operating a heat pump may dramatically increase. I’m wondering whether the cost to operate a natural gas furnace might exceed that of a heat pump down the road. To be honest, this question is really getting into the weeds and is probably trivial when discussing the pros and cons of heat pumps.
Gotcha, the reality is without a strong move to nuclear that slow rise in electricity prices unlikely. Commercial wind and solar are actually pretty expensive energy sources even with the claimed free fuel. The fact they can only run 25% to 35% of the time, and that run time is up to nature makes them an undependable source. They usually have to have gas generation in reserve to cover them and that is expensive .