3 ms·

This is a fair statement, but it represents an incomplete truth. Quick term run down, then some quick math. COP: Coefficient of Performance. This is a ratio of

This is a fair statement, but it represents an incomplete truth. Quick term run down, then some quick math. COP: Coefficient of Performance. This is a ratio of how much you can augment the temperature for every unit of energy you put in. Your best, most efficient top of the line gas furnace has a COP of 0.98. This means that, for every 1 joule of energy, you're getting 0.98 joules of heat energy. Let's say that, for easy math's sake, you pay $1 per joule for natural gas, so your operational cost for the furnace is $1.02 per joule. Yes, numbers are crazy town, but simple math for simple explanation. A modern bog-standard heat pump has a COP of 4. The operational COP of the heat pump varies depending on the difference in temperature from inside to outside, but the vast majority of the state of California is going to operate at temperatures that can support the COP. Per your statement, electricity is 6x the cost of gas, so we'll say that every joule of energy going into the heat pump costs $6. This puts your operational cost at $1.50 per joule. It's certainly not a "better deal", but the cost delta can't simply be measured by the cost of the energy going into the heating system.

sokoloff 3y ago
> most efficient top of the line gas furnace has a COP of 0.98 That's a steady-state, best-case figure that is almost never achieved in practice. Very long run times and very low temperature operation is required to achieve those figures, and most homes are not setup to create those conditions. I'd not be surprised to learn that most 95+% efficient furnaces run at 90% realized.
- voisin 3y ago
  This is super interesting. Do you have a source for this? I don’t doubt it, but I had never thought of it and it doesn’t surprise me that it is a misleading figure to begin with.
  - sokoloff 3y ago
    The difference (loss) between SSE and AFUE is intended to cover this effect, provided the equipment is sized correctly (almost never done and almost always at least 50% oversized, leading to short-cycling and greater spread between SSE and actual fuel use [meaning AFUE is overstated]). That might give some terms to Google and find additional data. Peak COP’s equivalent is closest to SSE; SCOP is closest to AFUE.

sokoloff 3y ago

> most efficient top of the line gas furnace has a COP of 0.98 That's a steady-state, best-case figure that is almost never achieved in practice. Very long run times and very low temperature operation is required to achieve those figures, and most homes are not setup to create those conditions. I'd not be surprised to learn that most 95+% efficient furnaces run at 90% realized.

voisin 3y ago
This is super interesting. Do you have a source for this? I don’t doubt it, but I had never thought of it and it doesn’t surprise me that it is a misleading figure to begin with.
- sokoloff 3y ago
  The difference (loss) between SSE and AFUE is intended to cover this effect, provided the equipment is sized correctly (almost never done and almost always at least 50% oversized, leading to short-cycling and greater spread between SSE and actual fuel use [meaning AFUE is overstated]). That might give some terms to Google and find additional data. Peak COP’s equivalent is closest to SSE; SCOP is closest to AFUE.