[_aavaa_]

Efficiency is not the correct word here.

A gas furnace converts 1 J of chemical potential energy (higher heating value for natural gas) into essentially 1 J of internal energy in the air (raising it’s temperature).

A heat pump can take 1 J of electricity and move (realistically) up to 5 J of internal energy from A to B.

A layman description (if not actually accurate) is that while a gas furnace (or electric resistive heating) can be 100% efficient, a heat pump can be 500% efficient.

[measurablefunc]

Can you point me to the actual literature on the mechanics of heat pumps b/c I don't think you're explaining properly what's going on. If you can get 5J out of 1J then you have a perpetual motion machine & those are physically & logically impossible (assuming physically relevant axioms).

[_aavaa_]

It's likely I am not.

Links below, tldrs here: A heat pump does what the name suggests: it pumps heat. Resistive heating and burning gas is converting energy from one form into another. A heat pumps moves energy from A to B (making A colder and B hotter in the process) in literally the same way AC units

You get 5 J of heat out for every 1 J of electricity in because we're being funny with the units. You put in 1 J of electricity and the rest is put in as heat from your source (A) and then moved into B.

A good YouTube video: https://www.youtube.com/watch?v=7J52mDjZzto

[measurablefunc]

That obviously doesn't make sense if you know basic physics. Converting gas into heat by combusting it heats up the air in the room directly. Burning that gas in a turbine & then transferring that energy through a bunch of transformers to get to the heat pump can't give you more heat than what went into combusting the gas in the first place. This obviously doesn't work in reverse to cool a room but the direction I laid out is obviously correct. You're not using funny units, you're confused about the thermodynamics of the situation. Heat pumps are more efficient air coolers than standard air conditioners but they're not giving you more energy than what you put into it.

[_aavaa_]

> you're confused about the thermodynamics of the situation.

I assure you I am not, it is actually you who still seem confused about where the energy is coming from.

> they're not giving you more energy than what you put into it.

When you burn gas in a furnace, all of the energy that raises the temperature of the house comes from the gas.

When you run a heat pump you have two sources of energy:

1. Electricity running the thing.

2. Heat from the outside that you're moving inside.

#2 is where most of the energy that actually heats up the house comes from. The electricity is used to move it from outside the house to inside.

> Burning that gas in a turbine & then transferring that energy through a bunch of transformers to get to the heat pump can't give you more heat than what went into combusting the gas in the first place.

It actually can. A combined cycle plant can be ~60% efficient (chemical energy -> electricity). Say another 70% for getting it from the plant to your heat pump, then a COP 3 (or "efficiency" of 300%) gives you 0.6x0.7x3 or 1.26. So for every J of natural gas you burn in that plant, you'll heat your house with 1.26 J (compared to at best 1 J, realistically 0.9 J, for a gas furnace).

If you instead look at a ground source heat pump, you can get a COP of ~7 [0]. You're now putting ~3 J of heat into your house of each J of natural gas.

[0]: https://en.wikipedia.org/wiki/Heat_pump#Performance

[measurablefunc]

That's clever accounting but your overall system (house + outside + plant + fuel) is still less than 100% efficient. That's basic physics/thermodynamics.

Heat pumps are basically taking advantage of solar + geothermal radiation that ends up in the ground & air but once you account for the solar + geo radiation then it becomes obvious that all a heat pump is doing is accelerating the production of entropy. You're either normalizing the delta between inside & outside or increasing it but in both cases the overall entropy of the system goes up. Whereas your accounting seems to suggest you somehow get more energy than what was available which is obviously unphysical.

[_aavaa_]

Sure.

But my accounting was always about the energy that we as humans need to supply. This discussion was originally about how talking about the energy transition in terms of primary energy is inherently misleading.

A heat pump does not magically create the difference between work input and heat output, it pulls it from second source. But that source is free. All we have to provide is the work.

Replacing a gas burner with a heat pump does not require us to replace 1 J of chemical potential energy with 1 J of electricity, instead replace it with 0.33 J of electricity (or even less).