Yes, I've considered getting a heat pump; for one reason and another, I can't.
It doesn't feel right to talk about the "efficiency" of a heat pump system; talk of "1W in gets you 3W out" isn't right, because you didn't magic those 3W out of thin air. It's more like "4W in gets you 4W out". It seems wrong to say that a heat pump system is "400% efficient".
I thought efficiency was a measure of how much of the work[0] going into a machine is transformed into the intended output work. I suppose you could say that this heat delivery machine is inefficient if a lot of the input work is expended on producing torque, or raising heavy stuff. But even that eventually turns into heat; just in the wrong place.
[0] I hope I'm using "work" and "machine" in the technical sense, so that "work" means displacement against a force, and a "machine" is any device for converting work from one form to another. Effiency is well-defined for that kind of machine: it's just the ratio of work in to work out, the output being what you want; so "efficiency" intrinsically depends on what your intentions are for your machine. .
> It doesn't feel right to talk about the "efficiency" of a heat pump system; talk of "1W in gets you 3W out" isn't right, because you didn't magic those 3W out of thin air. It's more like "4W in gets you 4W out". It seems wrong to say that a heat pump system is "400% efficient".
Those 3W didn't come out of thin air, it came from outside air.
1W of energy going into the heat pump causes 4W of heat energy to get moved from outside your house to the inside of your house.
That's the key thing to take note of. Traditional resistive heating works by turning electrical energy into heat energy directly. Heat pumps move heat energy the same way an A/C unit does, it just moves it the other way.
Essentially, a heat pump is just an A/C unit with the evaporator and the condenser flipped.
All heaters are 100% efficient in a closed system. However, your house is not a closed system. It’s a spatial region of an open system. In this context it makes sense to talk about efficiency as being lower or greater than 100%.
The efficiency is higher than input because the electricity is only used to transfer heat from one spot to another.
This is when the gas gets compressed, to get to the condensing stage at the high pressure. (+after burn for optimal efficiency)
It doesn't feel right to talk about the "efficiency" of a heat pump system; talk of "1W in gets you 3W out" isn't right, because you didn't magic those 3W out of thin air. It's more like "4W in gets you 4W out". It seems wrong to say that a heat pump system is "400% efficient".
I thought efficiency was a measure of how much of the work[0] going into a machine is transformed into the intended output work. I suppose you could say that this heat delivery machine is inefficient if a lot of the input work is expended on producing torque, or raising heavy stuff. But even that eventually turns into heat; just in the wrong place.
[0] I hope I'm using "work" and "machine" in the technical sense, so that "work" means displacement against a force, and a "machine" is any device for converting work from one form to another. Effiency is well-defined for that kind of machine: it's just the ratio of work in to work out, the output being what you want; so "efficiency" intrinsically depends on what your intentions are for your machine. .