5 ms·

End-to-end efficiency calculations are tricky and depend on a lot of variables.

• mindslight 3y ago
  Sure, but that doesn't mean you can throw your hands up and make an argument comparing nameplate efficiencies of things with different energy sources. I'm well aware the figure in my above comment could be off by a decent amount due to transmission efficiency, what specific plants are generating marginal power, etc. But it's at least framing the comparison right.
  • triceratops 3y ago
    Even in your worst case scenario, heat pumps are about as efficient end-to-end as a natural gas furnace. And renewable power is only going to become more common over time so it could get better. To a consumer, comparing nameplate efficiencies as you say makes the most sense. I can easily find out how much a joule of electricity and a joule of natural gas cost me. Then multiply those with efficiency to see which is cheaper.
    • mindslight 3y ago
      I did not put forth a worst case scenario. I put forth an example of doing proper comparison. Based on a figure I just saw from someone else describing their setup (1.75 COP at 5 deg F), and taking into account transmission losses etc, the worst case would seem to be significantly less efficient than burning natural gas directly in a condensing furnace. This isn't meant as some sort of knock against heat pumps! In fact I'm tentatively planning to add a heat pump to my own home within the next several years. Focusing on a worst case is still not an overall comparison of performance, but rather just one data point in the evaluation of a given design. Multiplying the cost of the energy source by the nameplate efficiency is indeed another sensible way of comparing across technologies. But that isn't what you did in your original comment, where you juxtaposed two different types of efficiency numbers. That was my only point in my original comment.