Heat Pump Payback in SeaTac, WA
SeaTac, WA: the heat pump payback math
SeaTac technically pencils out, but only past the point the equipment would need replacing anyway. $5,500 is what SeaTac would pay extra to go electric rather than replace the furnace and AC with the same again. That premium is recovered through $336 of lower running costs every year, landing the payback clock at roughly 16.4 years. SeaTac's own numbers say this pencils out only in theory, not in practice.
Checking a different city
This runs the same numbers for 3206 US cities, not just SeaTac. Look one up here.
The climate behind SeaTac's payback figure
SeaTac has a real but manageable winter, 4626 heating degree days a year against a 65°F base, and summers rarely ask much of an air conditioner, at 260 cooling degree days. 19°F is the figure equipment gets sized against here, the 99th-percentile cold snap, not an average day, with a low of 15.1°F in the 2024 station record. Worked through the model, that's a seasonal COP of 3.16 on the cold-climate unit fit for this climate. A cold-climate unit is the right call in SeaTac, below 25°F design temperature, a standard heat pump leans hard on electric-resistance backup, which erases most of the savings. Source: NOAA station Seattle-Tacoma International, 0.7 miles from SeaTac, the closest one on record.
SeaTac's running-cost comparison, in dollars
A 2000-square-foot house here would pull roughly 3,707 heating kilowatt-hours annually on top of cooling, totalling about $561 a year on electricity. SeaTac's gas rate of $17.62 per Mcf, applied to the 48 Mcf a year the furnace burns, puts the current furnace-and-AC running cost near $897 a year, against 14.27¢ per kWh for electricity. Priced as a standalone purchase, with a working furnace ripped out early, payback would take longer than the 15-year equipment life. Measured against the like-for-like replacement instead, a household here ends 15 years $454 behind.
How sensitive SeaTac's result is to prices
This result holds unless electricity climbs above 23.6¢/kWh (it is 14.27¢ now) or gas drops below $10.64 per Mcf (now $17.62); past either point, gas becomes the cheaper fuel in SeaTac. When quotes arrive, compare the heat pump price with a like-for-like furnace and AC replacement: at $336 a year saved, a difference under $2,352 pays back within 7 years here, and under $3,360 within 10.
If your home heats with electric baseboard instead of gas
Plenty of homes in SeaTac heat with electricity alone, no gas line involved. Swap the comparison to resistance heat instead of gas, and SeaTac's answer improves. Switching saves about $1,159 a year here, a heat pump moving heat rather than generating it needs far less electricity than resistance coils, so the extra $10,000 spent up front comes back in about 8.6 years.
SeaTac against the rest of the country
SeaTac lands at position 1064 out of 3206 cities on heating severity (coldest is 1), and 1210 out of 3206 by population size (biggest is 1). That's the coldest third of the dataset, where climate does most of the work behind this figure.
Next step if you live in SeaTac
About 34,024 people live in SeaTac, Washington, and every number on this page is what a contractor would actually work from when quoting a system here, the point isn't to replace that quote, it's to tell you whether to bother asking for one. Here, there's no cost penalty to waiting until your current furnace or AC actually needs replacing.
Ask a local HVAC contractor for a quote before committing either way.
Reading further on this page's numbers
The methodology guide walks through exactly how SeaTac's 3.16 seasonal COP and the rest of this page's numbers get built. At a 19°F design temperature, SeaTac sits in cold-climate territory; the guide to that class of unit explains why.