Mastodawn

Glenn Fleishman Jan 24, 2023

I now have almost four years of electricity and natural gas use for my house via our utility companies. We put in a heat pump in May 2022. Previously, we had two window ACs in bedrooms that we ran almost entirely at night (and only some nights) and a bunch of fans. Last summer, with intense heat, you can barely see an increase in usage—particularly when you factor in inflation and a slow climb upwards in rates. (These are all two-month billing periods and average temps.)

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Glenn Fleishman Jan 24, 2023

This winter, with some bitter cold temps for Seattle last month, it looks like we paid about 5% less with the heat pump than the same period last year. But it's likely we used substantially more therms to heat the house. (Still compiling that data; it's hard to get apples-to-apples.) This chart shows hours used for AC, heat pump heat, and nat-gas heat. (We're still using the nat-gas furnace a bit; need to consider whether turning it off turns into a maintenance problem.)

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Peter Smerdon Jan 24, 2023

@glennf Have you factored in the replacement cost of the inefficient existing devices?
If you maintained the status quo you would have to replace the wall ACs and furnace at some point.
You now have a heat pump at the beginning of its service life.

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Glenn Fleishman

@psmerdon You are smarter than I. The natural-gas furnace has a 20-30 year lifespan and it's 15! It costs $1,000s to replace. The AC units are relatively cheap—I think we spent in the very low hundreds. Also, I do think with excessive heat in Seattle, having a comfortable but not chilled refuge (we set our cooling to 79°F in the summer), we're likely giving ourselves longer, happier lives.