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I very nearly bought a heat pump for my house to replace (or augment) my natural gas furnace, but was dissuaded by the salesperson. He who pointed out that, wh

I very nearly bought a heat pump for my house to replace (or augment) my natural gas furnace, but was dissuaded by the salesperson. He who pointed out that, while heat pumps are miracles of efficiency, the electricity in my area is primarily generated by burning fossil fuels such as coal and natural gas. Due to transmission losses, it is cheaper, efficient, and greener to combust natural gas for warmth directly than to burn it at a power plant, feed the power into the grid, and use grid power to run a heat pump. Of course, running a heat pump allows you to take advantage of greener power sources when they become available, but his claim was that in a lot of places they don't really benefit the environment right now. Anyone have any numbers to back this up or refute it?

dzhiurgis 4y ago
I would just use heat pump for convenience alone. Not having monoxide and NOx risks around the house is another one.
cjrp 4y ago
> Due to transmission losses, it is cheaper, efficient, and greener to combust natural gas for warmth directly than to burn it at a power plant, feed the power into the grid, and use grid power to run a heat pump. That would certainly be true for a classic electric (element) heater, but I thought the point of heat pumps was that they’re not generating heat just… pumping it.
- benj111 4y ago
  I'm not convinced either a heat pump has a cop of ~4. A thermal power plant is ~50% efficient and transmission isn't losing 50% of the energy. This also ignores any greening of the grid, present and future. And the fact that a furnace/boiler isn't 100% efficient.
  - groestl 4y ago
    > A thermal power plant is ~50% efficient For electricity alone, I'd want to add. With heat coupling and district heating, thermal power plants can reach ~90% efficiency.
ben7799 4y ago
He's probably ignoring the externalities like the gas leaks on the way to your house or the power plant being able to have a huge scrubber that reduces emissions compared to what you can have at your house. The most important reason is there was probably a financial incentive from the manufacturer of the gas/oil furnace that made it more profitable for him to sell you that. Here we have such a massive state rebate on heat pumps, you have to literally have a lot of money and politics that equate to having your head up your backside to get a new gas/oil furnace. It's larger than an EV rebate and a much higher % of the total cost so you'd have to have a really good reason to stick with fossil fuels.
- jtchang 4y ago
  What state?
- the_third_wave 4y ago
  > He's probably ignoring the externalities like the gas leaks on the way to your house Where I live (Sweden) and come from (the Netherlands) gas leaks tend to get fixed since they are both costly as well as dangerous. Let's assume that this is not a real issue unless you have some data which points out the opposite. > the power plant being able to have a huge scrubber that reduces emissions We're not talking about heating a house using coal - which is where those scrubbers come in - but with gas. Gas fired power plants do not need scrubbers since they do not produce fly ash or sulphurous oxides, nor do gas-fired heaters. Total systems efficiency for a single-cycle gas-fired power plant lies between 32% to 38% for simple cycle gas turbines, most of those in the USA are closer to the first number. Combined cycle gas/steam turbines can run at up to 60% total efficiency which is about as high as it is possible to get using a thermal power generator [1]. The efficiency of gas-fired heaters lies somewhere between 70% and 95% or more, the upper range is common here in Europe. A good indicator for the efficiency is the fact that these appliances often use plastic flue pipes which is made possible by the fact that flue gas temperatures lie below 70°C. The effective COP for air/air heat pumps is highly dependent on the temperature difference between the hot and cold side, the colder it is outside the lower the efficiency. I don't know where the original poster lives so it is hard to calculate the expected efficiency. If it is anywhere where the temperature goes down below zero (Celcius) it is more than likely that the salesman was right since the effective COP ends up below 2 - and goes down to 1 or lower around -15°C to -30°C (depending on the model heat pump used, the amount of moisture in the air (moist air condenses and freezes on the evaporator which requires a thaw cycle which markedly lowers the efficiency). [1] https://www.brighthubengineering.com/power-plants/72369-compare-the-efficiency-of-different-power-plants/ https://www.brighthubengineering.com/power-plants/72369-comp...
fghorow 4y ago
Not to mention the Carnot efficiency losses causing ~50-70% of the heat energy at the generator to go out its cooling system. Yes, It's not clear at all that heat pumps are always a win -- depending on the energy source mix of your local grid. But with a COP of 3-4 (i.e. 3-4 times more heat is moved by the pump than is supplied as electrical energy) if there's a decent renewable contribution to electrical generation on your local grid, it might well be a win in terms of CO2 emissions. YMMV.
- PaulDavisThe1st 4y ago
  > Yes, It's not clear at all that heat pumps are always a win -- depending on the energy source mix of your local grid As others have noted, a new gas furnace might break even right now with an electric air-source heat pump, but how is it going to work out as electrification and decarbonization proceeds? Break even now, come out ahead in the future - choose heat pumps.
MrFoof 4y ago
The salesman could very well be correct. The reality is the numbers are incredibly contextual relative to specifically where you live. A great example of this exercise was Harry Metcalfe actually doing the digging and the math to attempt to objectively measure his impact, and whether an EV or PHEV made sense as a daily given where he specifically lives in the UK is primarily powered by coal: https://youtu.be/k15n6QAe8cE https://youtu.be/k15n6QAe8cE For him, right now, PHEV was lower impact, but he makes it clear that that will very likely change over time, and that if he lived elsewhere, he likely would’ve went EV. - - - - - This is a classic example of, “it depends.” If you live in an era with lots of sustainable energy, it’s likely a no brainer, but the math changes if you lived in an area powered by a lot of natural gas, or around Appalachia which is still predominantly coal. To answer the question, you have to get the information and do the math to understand what decision you want to make, given your requirements and goals. - - - - - For the record, Harry’s Garage (and Harry’s Farm) is a gem of YouTube’s car community. He doesn’t need it to make money, so he just does what he wants and goes down a lot of very nerdy rabbit holes (including sustainable energy, gov’t farm and energy policies), and actually USES his cars for REAL trips — like taking his Testarossa through the Sahara, etc. Harry was basically an “eccentric super car owner” in the 80s/90s (and ghost wrote articles in UK car mags for a while as an “anonymous/eccentric super car owner”) that ultimately founded EVO Magazine, helped influence a lot of the cinematic direction for the Top Gear reboot in the early 2000s, and was the inspiration for “Clarkson’s Farm.” He’s a nerd’s nerd, and an absolute treasure.
- grey-area 4y ago
  He’s also wrong, or at least wrong for anyone considering the question now. The UK is phasing out coal completely in the next few years and aggressively pursuing renewables. https://en.m.wikipedia.org/wiki/List_of_active_coal-fired_power_stations_in_the_United_Kingdom https://en.m.wikipedia.org/wiki/List_of_active_coal-fired_po...
  - jonatron 4y ago
    Yep, the youtube video at 21:25 contains a screenshot of UK electricity generation mix over a 4 week period in 2020, which was 0.3% coal.
electric_mayhem 4y ago
Salespeople are often ignorant af. I have both a heat pump and a gas furnace. I program my thermostat with: - Electric cost per kWh - Gas cost per therm - Heat pump afue - Furnace efficiency It does the math and runs whichever is cheaper. This past winter, the heat pump was cheaper down to 5 degrees Fahrenheit.
- mrguyorama 4y ago
  >Salespeople are often ignorant af. Or so much worse; they learned something for one specific situation/time and now apply it to everything because they don't realize that's not how it works. Sounds like this one might at least be aware of the complexities and nuance of the situation though.
- koolba 4y ago
  > I program my thermostat with: ... What thermostat let's you input all these data points?
  - electric_mayhem 4y ago
    Trane xl1050. Requires getting into technician config mode, which I’m pretty sure could result in rendering it inoperable if I screwed with the wrong settings. But it’s doable; I go through the process whenever my utility company changes their rates.
ars 4y ago
He's kinda wrong unless you live in the northern part of the country. A heat pump is a multiplyer - it takes that incoming energy and can get a multiple of heat (the exact multiple is the rating of the pump and varies). That's where the part of the country comes in - in the north the multiplyer is lower, in the south it's higher. With a nice high multiplyer it's a great deal. I wish though, that they had natural gas based heat pump - now THOSE would be really efficient!
- jeffbee 4y ago
  You can buy propane-fired refrigerators so I do not see why you couldn't make such a thing. You can also buy heat pumps where propane is the working fluid, which is vaguely ironic.
- nkurz 4y ago
  Natural gas powered heat pumps actually exist, and are commercially available, although rare in North America. Most use an ammonia absorption cycle. Efficiency is lower than one might be hoping, quite a bit less than 2x. Here's a Canadian study evaluating one: https://sustainabletechnologies.ca/home/heating-and-cooling/evaluation-of-a-gas-absorption-heat-pump-archetype-house-vaughan/ https://sustainabletechnologies.ca/home/heating-and-cooling/....
marssaxman 4y ago
That can't be right. Heat pumps are commonly 2.5x-4x more efficient than direct heating. "The U.S. Energy Information Administration (EIA) estimates that annual electricity transmission and distribution (T&D) losses averaged about 5% of the electricity transmitted and distributed in the United States in 2017 through 2021." https://www.eia.gov/tools/faqs/faq.php?id=105&t=3 https://www.eia.gov/tools/faqs/faq.php?id=105&t=3
- sokoloff 4y ago
  The combustion efficiency of the fossil fuel electric generation must also be considered. If that’s 40% efficient, a heat pump with a CoP of 2.5 is very close to a 95% AFUE gas-burning unit.
  - pornel 4y ago
    Combined cycle gas power plants are about 60% efficient. Coal power plants are around 40%, but even the dirtiest parts of Florida aren't all coal (https://app.electricitymaps.com/map https://app.electricitymaps.com/map) But of course this is short-sighted, because the grid is greener in most places, and will get even greener over the lifetime of the heat pump, while the gas furnace won't get any better.
- nkurz 4y ago
  I downvoted you for your overconfidence. Your conclusion might be right, but it's not as straightforward as you suggest. You're right that the transmission losses aren't large, but you seem to be missing the much bigger losses involved in generating electricity from coal. Currently, the average coal fired plant produces electricity at 33% efficiency: https://www.energy.gov/fecm/transformative-power-systems https://www.energy.gov/fecm/transformative-power-systems. That's average, so there are probably plants out there producing at 30%. If we assume another 5% loss for transmission, this takes us down to 25% efficiency as delivered to the consumer. If a heat pump is 3x the efficiency of resistance electric heat, but you are burning 4x the coal to generate the electricity, are you still certain that a 95% natural gas furnace is never the better choice for efficiency? I'm not. I think the heat pump is probably more efficient in many cases, but I wouldn't eliminate the possibility that there are cases where the natural gas wins.
jeffbee 4y ago
Doesn't sound like this person is educated in thermodynamics. Which is why the law needs to step in and just outlaw or tax mineral gas appliances. Letting some petro-poisoned goof talk citizens out of buying electric heat pumps is suboptimal.
kibwen 4y ago
Keep in mind that gas infrastructure is leaky, which means that between two to seven percent of the gas that is pumped to your home is lost to the atmosphere before it arrives (depending on the age and maintenance status of the gas pipes in your area). Methane is a very potent greenhouse gas, and this leakage can easily tip the scales back in favor of heat pumps, even with electric transmission losses.
- colechristensen 4y ago
  But does it leak in a dose-dependent way? Is there a marginal increase in leakage if you pick a gas furnace over an electric heat pump?
maccard 4y ago
> Anyone have any numbers to back this up or refute it? Don't know where you are, but here in the UK right now the split is 34% wind, 29% gas, remaining <other> [0]. If you migrated from a modern condensing boiler with 90% efficiency to a heat pump with 300% efficiency (1 unit of electricity outputs 3 units of heat), then with the gas condensing boiler you're getting 0.9 units of heat per unit of gas, and with a heat pump you're getting 0.87 units of heat per unit of gas, _plus_ 1 unit of heat from wind. Over the last year, the _majority_ of the time the split in generation sources looks like this. It's occasionly heavier on gas, but for 11 months of the year, it's a no brainer, and I don't think that outdoes the 1-2 weeks per year that you're using an almost equivalent amount of gas. [0] https://grid.iamkate.com/ https://grid.iamkate.com/
rainsford 4y ago
Whether or not that's true for your particular situation is going to be very location dependent, but I think the salesperson is fairly wrong in the general case in the US. Fossil fuel generation accounts for about 60% of US electricity and natural gas electricity generation is around 50% efficient. Another 5-10% is lost due to transmission, so say around 40% of the energy potential of a natural gas power plant makes its way to your house as electricity. Combine those and it means that every 1Wh of electrical energy generated takes the equivalent of 1.5Wh worth of natural gas. That doesn't sound particularly good, since new natural gas furnaces can be around 90% efficient, meaning that same 1.5Wh of natural gas could produce 1.35Wh worth of heating. Except heat pumps have an efficiency of around 2.5-3, meaning for every 1Wh of electrical energy they consume, they produce 2.5-3Wh worth of heat. That means producing 3Wh worth of heat with a heat pump consumes 1.5Wh worth of natural gas in the standard US electrical energy mix. Getting that same 3Wh worth of heat directly from a natural gas furnace would take over twice the amount of natural gas. Even if your electricity generation is 100% natural gas, the heat pump would be very competitive with natural gas. Now if you live in an area that gets really cold (meaning heat pump efficiency on average is lower) and all your electricity is generated by an old coal power plant (which is less efficient and dirtier), natural gas heating may actually be a greener option for now. But on average that's not the case and many places in the US have much better green fundamentals for heat pumps thanks to mild temperatures and/or lots of non-fossil fuel energy generation.
- the_third_wave 4y ago
  > natural gas electricity generation is around 50% efficient The real number is far lower for the majority of power plants using simple/single-cycle turbines which end up somewhere between 32% and 38% [1]. Combined-cycle can go up to 60%, CHP (heat and power) can be up to 80% efficient. [1] https://www.brighthubengineering.com/power-plants/72369-compare-the-efficiency-of-different-power-plants/ https://www.brighthubengineering.com/power-plants/72369-comp...
- pandaman 4y ago
  >so say around 40% of the energy potential of a natural gas power plant makes its way to your house as electricity. Combine those and it means that every 1Wh of electrical energy generated takes the equivalent of 1.5Wh worth of natural gas. If the efficiency is 40% it means 1Wh of gas energy produces 0.4Wh of electricity, does not it? How is it possible then to get 1Wh of electricity using just 1.5Wh worth of gas? 1Wh = 2.5*(0.4Wh).
dev_tty01 4y ago
Heat pump with gas auxiliary heat for cold nights. That's what we run and it is the best of both worlds.
kerpotgh 4y ago
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dzhiurgis 4y ago

I would just use heat pump for convenience alone. Not having monoxide and NOx risks around the house is another one.

cjrp 4y ago

> Due to transmission losses, it is cheaper, efficient, and greener to combust natural gas for warmth directly than to burn it at a power plant, feed the power into the grid, and use grid power to run a heat pump. That would certainly be true for a classic electric (element) heater, but I thought the point of heat pumps was that they’re not generating heat just… pumping it.

benj111 4y ago
I'm not convinced either a heat pump has a cop of ~4. A thermal power plant is ~50% efficient and transmission isn't losing 50% of the energy. This also ignores any greening of the grid, present and future. And the fact that a furnace/boiler isn't 100% efficient.
- groestl 4y ago
  > A thermal power plant is ~50% efficient For electricity alone, I'd want to add. With heat coupling and district heating, thermal power plants can reach ~90% efficiency.

ben7799 4y ago

He's probably ignoring the externalities like the gas leaks on the way to your house or the power plant being able to have a huge scrubber that reduces emissions compared to what you can have at your house. The most important reason is there was probably a financial incentive from the manufacturer of the gas/oil furnace that made it more profitable for him to sell you that. Here we have such a massive state rebate on heat pumps, you have to literally have a lot of money and politics that equate to having your head up your backside to get a new gas/oil furnace. It's larger than an EV rebate and a much higher % of the total cost so you'd have to have a really good reason to stick with fossil fuels.

jtchang 4y ago
What state?
the_third_wave 4y ago
> He's probably ignoring the externalities like the gas leaks on the way to your house Where I live (Sweden) and come from (the Netherlands) gas leaks tend to get fixed since they are both costly as well as dangerous. Let's assume that this is not a real issue unless you have some data which points out the opposite. > the power plant being able to have a huge scrubber that reduces emissions We're not talking about heating a house using coal - which is where those scrubbers come in - but with gas. Gas fired power plants do not need scrubbers since they do not produce fly ash or sulphurous oxides, nor do gas-fired heaters. Total systems efficiency for a single-cycle gas-fired power plant lies between 32% to 38% for simple cycle gas turbines, most of those in the USA are closer to the first number. Combined cycle gas/steam turbines can run at up to 60% total efficiency which is about as high as it is possible to get using a thermal power generator [1]. The efficiency of gas-fired heaters lies somewhere between 70% and 95% or more, the upper range is common here in Europe. A good indicator for the efficiency is the fact that these appliances often use plastic flue pipes which is made possible by the fact that flue gas temperatures lie below 70°C. The effective COP for air/air heat pumps is highly dependent on the temperature difference between the hot and cold side, the colder it is outside the lower the efficiency. I don't know where the original poster lives so it is hard to calculate the expected efficiency. If it is anywhere where the temperature goes down below zero (Celcius) it is more than likely that the salesman was right since the effective COP ends up below 2 - and goes down to 1 or lower around -15°C to -30°C (depending on the model heat pump used, the amount of moisture in the air (moist air condenses and freezes on the evaporator which requires a thaw cycle which markedly lowers the efficiency). [1] https://www.brighthubengineering.com/power-plants/72369-compare-the-efficiency-of-different-power-plants/ https://www.brighthubengineering.com/power-plants/72369-comp...

fghorow 4y ago

Not to mention the Carnot efficiency losses causing ~50-70% of the heat energy at the generator to go out its cooling system. Yes, It's not clear at all that heat pumps are always a win -- depending on the energy source mix of your local grid. But with a COP of 3-4 (i.e. 3-4 times more heat is moved by the pump than is supplied as electrical energy) if there's a decent renewable contribution to electrical generation on your local grid, it might well be a win in terms of CO2 emissions. YMMV.

PaulDavisThe1st 4y ago
> Yes, It's not clear at all that heat pumps are always a win -- depending on the energy source mix of your local grid As others have noted, a new gas furnace might break even right now with an electric air-source heat pump, but how is it going to work out as electrification and decarbonization proceeds? Break even now, come out ahead in the future - choose heat pumps.

MrFoof 4y ago

The salesman could very well be correct. The reality is the numbers are incredibly contextual relative to specifically where you live. A great example of this exercise was Harry Metcalfe actually doing the digging and the math to attempt to objectively measure his impact, and whether an EV or PHEV made sense as a daily given where he specifically lives in the UK is primarily powered by coal: https://youtu.be/k15n6QAe8cE https://youtu.be/k15n6QAe8cE For him, right now, PHEV was lower impact, but he makes it clear that that will very likely change over time, and that if he lived elsewhere, he likely would’ve went EV. - - - - - This is a classic example of, “it depends.” If you live in an era with lots of sustainable energy, it’s likely a no brainer, but the math changes if you lived in an area powered by a lot of natural gas, or around Appalachia which is still predominantly coal. To answer the question, you have to get the information and do the math to understand what decision you want to make, given your requirements and goals. - - - - - For the record, Harry’s Garage (and Harry’s Farm) is a gem of YouTube’s car community. He doesn’t need it to make money, so he just does what he wants and goes down a lot of very nerdy rabbit holes (including sustainable energy, gov’t farm and energy policies), and actually USES his cars for REAL trips — like taking his Testarossa through the Sahara, etc. Harry was basically an “eccentric super car owner” in the 80s/90s (and ghost wrote articles in UK car mags for a while as an “anonymous/eccentric super car owner”) that ultimately founded EVO Magazine, helped influence a lot of the cinematic direction for the Top Gear reboot in the early 2000s, and was the inspiration for “Clarkson’s Farm.” He’s a nerd’s nerd, and an absolute treasure.

grey-area 4y ago
He’s also wrong, or at least wrong for anyone considering the question now. The UK is phasing out coal completely in the next few years and aggressively pursuing renewables. https://en.m.wikipedia.org/wiki/List_of_active_coal-fired_power_stations_in_the_United_Kingdom https://en.m.wikipedia.org/wiki/List_of_active_coal-fired_po...
- jonatron 4y ago
  Yep, the youtube video at 21:25 contains a screenshot of UK electricity generation mix over a 4 week period in 2020, which was 0.3% coal.

electric_mayhem 4y ago

Salespeople are often ignorant af. I have both a heat pump and a gas furnace. I program my thermostat with: - Electric cost per kWh - Gas cost per therm - Heat pump afue - Furnace efficiency It does the math and runs whichever is cheaper. This past winter, the heat pump was cheaper down to 5 degrees Fahrenheit.

mrguyorama 4y ago
>Salespeople are often ignorant af. Or so much worse; they learned something for one specific situation/time and now apply it to everything because they don't realize that's not how it works. Sounds like this one might at least be aware of the complexities and nuance of the situation though.
koolba 4y ago
> I program my thermostat with: ... What thermostat let's you input all these data points?
- electric_mayhem 4y ago
  Trane xl1050. Requires getting into technician config mode, which I’m pretty sure could result in rendering it inoperable if I screwed with the wrong settings. But it’s doable; I go through the process whenever my utility company changes their rates.

ars 4y ago

He's kinda wrong unless you live in the northern part of the country. A heat pump is a multiplyer - it takes that incoming energy and can get a multiple of heat (the exact multiple is the rating of the pump and varies). That's where the part of the country comes in - in the north the multiplyer is lower, in the south it's higher. With a nice high multiplyer it's a great deal. I wish though, that they had natural gas based heat pump - now THOSE would be really efficient!

jeffbee 4y ago
You can buy propane-fired refrigerators so I do not see why you couldn't make such a thing. You can also buy heat pumps where propane is the working fluid, which is vaguely ironic.
nkurz 4y ago
Natural gas powered heat pumps actually exist, and are commercially available, although rare in North America. Most use an ammonia absorption cycle. Efficiency is lower than one might be hoping, quite a bit less than 2x. Here's a Canadian study evaluating one: https://sustainabletechnologies.ca/home/heating-and-cooling/evaluation-of-a-gas-absorption-heat-pump-archetype-house-vaughan/ https://sustainabletechnologies.ca/home/heating-and-cooling/....

marssaxman 4y ago

That can't be right. Heat pumps are commonly 2.5x-4x more efficient than direct heating. "The U.S. Energy Information Administration (EIA) estimates that annual electricity transmission and distribution (T&D) losses averaged about 5% of the electricity transmitted and distributed in the United States in 2017 through 2021." https://www.eia.gov/tools/faqs/faq.php?id=105&t=3 https://www.eia.gov/tools/faqs/faq.php?id=105&t=3

sokoloff 4y ago
The combustion efficiency of the fossil fuel electric generation must also be considered. If that’s 40% efficient, a heat pump with a CoP of 2.5 is very close to a 95% AFUE gas-burning unit.
- pornel 4y ago
  Combined cycle gas power plants are about 60% efficient. Coal power plants are around 40%, but even the dirtiest parts of Florida aren't all coal (https://app.electricitymaps.com/map https://app.electricitymaps.com/map) But of course this is short-sighted, because the grid is greener in most places, and will get even greener over the lifetime of the heat pump, while the gas furnace won't get any better.
nkurz 4y ago
I downvoted you for your overconfidence. Your conclusion might be right, but it's not as straightforward as you suggest. You're right that the transmission losses aren't large, but you seem to be missing the much bigger losses involved in generating electricity from coal. Currently, the average coal fired plant produces electricity at 33% efficiency: https://www.energy.gov/fecm/transformative-power-systems https://www.energy.gov/fecm/transformative-power-systems. That's average, so there are probably plants out there producing at 30%. If we assume another 5% loss for transmission, this takes us down to 25% efficiency as delivered to the consumer. If a heat pump is 3x the efficiency of resistance electric heat, but you are burning 4x the coal to generate the electricity, are you still certain that a 95% natural gas furnace is never the better choice for efficiency? I'm not. I think the heat pump is probably more efficient in many cases, but I wouldn't eliminate the possibility that there are cases where the natural gas wins.

jeffbee 4y ago

Doesn't sound like this person is educated in thermodynamics. Which is why the law needs to step in and just outlaw or tax mineral gas appliances. Letting some petro-poisoned goof talk citizens out of buying electric heat pumps is suboptimal.

kibwen 4y ago

Keep in mind that gas infrastructure is leaky, which means that between two to seven percent of the gas that is pumped to your home is lost to the atmosphere before it arrives (depending on the age and maintenance status of the gas pipes in your area). Methane is a very potent greenhouse gas, and this leakage can easily tip the scales back in favor of heat pumps, even with electric transmission losses.

colechristensen 4y ago
But does it leak in a dose-dependent way? Is there a marginal increase in leakage if you pick a gas furnace over an electric heat pump?

maccard 4y ago

> Anyone have any numbers to back this up or refute it? Don't know where you are, but here in the UK right now the split is 34% wind, 29% gas, remaining <other> [0]. If you migrated from a modern condensing boiler with 90% efficiency to a heat pump with 300% efficiency (1 unit of electricity outputs 3 units of heat), then with the gas condensing boiler you're getting 0.9 units of heat per unit of gas, and with a heat pump you're getting 0.87 units of heat per unit of gas, _plus_ 1 unit of heat from wind. Over the last year, the _majority_ of the time the split in generation sources looks like this. It's occasionly heavier on gas, but for 11 months of the year, it's a no brainer, and I don't think that outdoes the 1-2 weeks per year that you're using an almost equivalent amount of gas. [0] https://grid.iamkate.com/ https://grid.iamkate.com/

rainsford 4y ago

Whether or not that's true for your particular situation is going to be very location dependent, but I think the salesperson is fairly wrong in the general case in the US. Fossil fuel generation accounts for about 60% of US electricity and natural gas electricity generation is around 50% efficient. Another 5-10% is lost due to transmission, so say around 40% of the energy potential of a natural gas power plant makes its way to your house as electricity. Combine those and it means that every 1Wh of electrical energy generated takes the equivalent of 1.5Wh worth of natural gas. That doesn't sound particularly good, since new natural gas furnaces can be around 90% efficient, meaning that same 1.5Wh of natural gas could produce 1.35Wh worth of heating. Except heat pumps have an efficiency of around 2.5-3, meaning for every 1Wh of electrical energy they consume, they produce 2.5-3Wh worth of heat. That means producing 3Wh worth of heat with a heat pump consumes 1.5Wh worth of natural gas in the standard US electrical energy mix. Getting that same 3Wh worth of heat directly from a natural gas furnace would take over twice the amount of natural gas. Even if your electricity generation is 100% natural gas, the heat pump would be very competitive with natural gas. Now if you live in an area that gets really cold (meaning heat pump efficiency on average is lower) and all your electricity is generated by an old coal power plant (which is less efficient and dirtier), natural gas heating may actually be a greener option for now. But on average that's not the case and many places in the US have much better green fundamentals for heat pumps thanks to mild temperatures and/or lots of non-fossil fuel energy generation.

the_third_wave 4y ago
> natural gas electricity generation is around 50% efficient The real number is far lower for the majority of power plants using simple/single-cycle turbines which end up somewhere between 32% and 38% [1]. Combined-cycle can go up to 60%, CHP (heat and power) can be up to 80% efficient. [1] https://www.brighthubengineering.com/power-plants/72369-compare-the-efficiency-of-different-power-plants/ https://www.brighthubengineering.com/power-plants/72369-comp...
pandaman 4y ago
>so say around 40% of the energy potential of a natural gas power plant makes its way to your house as electricity. Combine those and it means that every 1Wh of electrical energy generated takes the equivalent of 1.5Wh worth of natural gas. If the efficiency is 40% it means 1Wh of gas energy produces 0.4Wh of electricity, does not it? How is it possible then to get 1Wh of electricity using just 1.5Wh worth of gas? 1Wh = 2.5*(0.4Wh).

dev_tty01 4y ago

Heat pump with gas auxiliary heat for cold nights. That's what we run and it is the best of both worlds.

kerpotgh 4y ago

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