Edit: since i am getting downvoted to oblivion, let me fight back here. I genuinely wished heat pumps would be more efficient and in theory they can be. I would love to not generate heat and just use the outside heat energy and compress it down into a smaller location.
But compressing and decompressing is not an energy efficient task. It takes a lot of work. Mechanical inefficiencies are a huge energy consumption. Gas is simply burning fuel. Yes, we should save gas for rainy days. But I hate to say that it is more efficient and cheap. There is no comparison.
https://en.wikipedia.org/wiki/Combined_cycle_power_plant
> (CCGT) plant[s] achieve a best-of-class [...] thermal efficiency of around 64% in base-load operation. In contrast, a single cycle steam power plant is limited to efficiencies from 35 to 42%
This is a huge problem in Europe where a house is expected to last a 100 years, in many areas much more.
The core idea is that you aren’t using 1 unit of electrical energy to create 1 new unit of heat energy. You are using 1 unit of electrical energy to capture several units of pre-existing heat energy from the environment and pump it indoors.
Burning 1 joule of gas would give you 1 joule of heat in a perfect world. That is what a non pump does.
An expensive high efficiency gas furnace might be 95% efficient (most normal furnaces are in the 80's)
1000 x 0.95 = 950 BTU/cuft
A high efficiency natural gas power plant is 60% efficient and a modern high efficiency low temp heat pump can have a COP up to around 2.7 at 17F
1000 x 0.6 x 2.7 = 1620 BTU/cuft
A 40% power pant is still more efficient than a 95% furnace with a 2.7 COP heat pump.
There is obviously more to this, there are some grid losses to account for but has to be compared to piping losses, there is also cost factors and also how much renewable is mixed into your grid supply, but generally once that heat pump is above around 2.5 COP it starts to make sense, this is a no brainer in milder climates which is why I have a heat pump and no gas furnace here in FL even though I have gas to the house for other uses.
They're a no-brainer in every climate. Newer heat pumps can handle fairly cold temperatures (-13°F) pretty easily, there may be a loss in efficiency but in the majority of the world it doesn't stay that cold. A few days of lower than normal efficiency, and at worst plugging in a few space heaters if it gets extremely cold for a day or two, does not change the overall math of heat pumps being a better solution.
Hell, that's just me talking about air source heat pumps. No reason for new construction to not use ground source and get better efficiency and not worry about ambient outdoor temperatures.
That isn't to say they cannot work I personally have a heat pump in my house and it worked fine through the -15F weather we got. But it requires careful design work initially. Also you run into simply size constraints where residential heat pumps tend to max out at 5 tons (60k BTUs) typically when furnaces can easily get up into the 100k+ BTUs. Which might require multiple heat pumps and separating existing duct work. But definitely new construction should start designing around these constraints now.
I am looking for genuine research, and not from paid mouth pieces.
Majority of the comments here seem like agents of heat pump industry. And HN rules forbid me from calling them that.
In extreme climates, gas burning is cheaper. And quite clean. There are some objections because of delivery leaks, but that is a separate concern.
Switching everyone to heat pumps would lower emissions from heating and cooling in the US by 160m tonnes a year [1], which is something like 30-40%.
It's true that upfront costs of heat pumps can be higher, but thanks to the IRA there are huge subsidies available (and further subsidies in many states) which make up most or even all of that difference. The lifetime costs of heat pumps with these subsidies should be substantially lower than high efficiency natural gas furnaces.
[1] https://www.rewiringamerica.org/circuit-breakers-heat-pumps
(Those subsidies, by the way, are one of the reasons "everybody is talking about heat pumps")
Those compressions and decompressions take up immense amounts of energy. They are less efficient than simply burning gas. On the flip side, could we not create electricity generation and heating from Natural gas?
Most of the energy is coming from the ambient air, only a small amount of electricity is used to change what temperature that energy is available at.
[1] A very simple mental model you can use to understand the difference between temperature and energy for a gas is that temperature is the number of times the gas molecules bump into each other in a second, while energy is how fast the gas molecules are moving. So if you have a very low pressure gas, even all of those molecules have a ton of energy in the form of motion, the temperature of the gas will be quite low because the gas molecules won't interact often. But compress that gas down to a small volume, and the molecules will bump into each other all the time even though they don't have much more energy.
Cost is going to vary greatly on the electricity and gas prices in your area, so it's hard to give a definitive answer there.
With regards to energy efficiency, my understanding is that heat pumps can be up to 400% (300% typical), which is naively much better than gas which is at most 90% efficient (70-80% typical). This doesn't take into account the extra innefficiency of generating the electricity in the first place, but a quick google tells me coal plants are typically 33% efficient, with combined cycle gas plants being typically being 50% efficient. Even at those levels, heat pumps still look to be coming out ahead to me. And that's not even taking into the possibility of green energy generation through renewables or nuclear.
>But compressing and decompressing is not an energy efficient task. It takes a lot of work. Mechanical inefficiencies are a huge energy consumption. Gas is simply burning fuel. Yes, we should save gas for rainy days. But I hate to say that it is more efficient and cheap. There is no comparison.
You are very mistaken, the energy required to compress refrigerant is less than the energy captured and delivered if COP > 1, which is the point of a heat pump. At COP 1 it is basically heat of compression and equal to a resistive heater at COP greater than 2 the heat pump captured more heat from the environment than used to compress the refrigerant.
I am not sure if you are arguing in good faith, if so here are some of the simplest resources I can find to explain how a heat pump can exceed a furnace in efficiency even when taking power plant and transmission losses into account, with easy to understand graphics:
https://greenbusinesswatch.co.uk/cop-vs-spf
https://energyeducation.ca/encyclopedia/Coefficient_of_perfo...
http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/heatpump.h...
This should really be taught and drilled in lower education, the difference between heat and temperature and relationship to power, how heat engines work, etc. This stuff basically makes modern society possible and we will never progress in decoupling our power sources from use of the power which is what electrification allows which allows us to transition away from throwing carbon up in the air for energy.
