Is a heat pump worth it in Mill Creek?
In Mill Creek, the math is close enough that it comes down to how long you plan to stay. $3,500 is what Mill Creek would pay extra to go electric rather than replace the furnace and AC with the same again, once the $2,000 federal credit is applied. Mill Creek's residents would see roughly $318 a year back in running costs, putting the payback around 11 years. Whether that's worth it in Mill Creek depends on how many years you expect to own the place.
Why Mill Creek's climate drives this number
4489 heating degree days pile up here every year, so Mill Creek has a real but manageable winter; the cooling side runs to 200 cooling degree days, where summers rarely ask much of an air conditioner. 18°F is the figure equipment gets sized against here — the 99th-percentile cold snap, not an average day — with a record low of 12.9°F on file. Worked through the model, that's a seasonal COP of 3.13 on the cold-climate unit fit for this climate. A cold-climate unit is the right call in Mill Creek — below 25°F design temperature, a standard heat pump leans hard on electric-resistance backup, which erases most of the savings. Climate figures trace to the nearest NOAA station, SNOHOMISH CO (PAINE FD) AP, 4.4 miles from Mill Creek.
What it actually costs to run, year to year
Modelled on a typical 2000-square-foot house, the heat pump draws about 3,632 kWh a year to keep it warm, plus cooling, for a combined electric bill near $543 a year. The gas furnace it replaces burns roughly 47 Mcf a year at 17.62 per Mcf here, for a running cost near $861 a year (electricity here runs 14.27¢/kWh). Looked at as a full purchase rather than an incremental one, payback here is roughly 42.4 years, leaving the 15-year total $1,273 ahead.
If your home heats with electric baseboard instead of gas
Not every home in Mill Creek has gas service. Swap the comparison to resistance heat instead of gas, and Mill Creek's answer improves. About $1,116 a year comes back this way, enough that the 7.2-year payback clears the $8,000 premium comfortably within the equipment's life.
Mill Creek against the rest of the country
Among 3206 cities, Mill Creek's winter puts it at rank 1209 for severity, while its size puts it at rank 1849 for population — 1 in both cases being the extreme. That's the middle third for winter severity among the cities covered here.
Deciding what's next in Mill Creek, WA
About 20,993 people live in Mill Creek, 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.
More on how this number was built
Every constant behind this page — the 3.13 seasonal COP, the degree-day corrections, the equipment costs — is documented in the methodology guide. Mill Creek's 18°F design temperature is below the 25°F line, which is why a cold-climate unit is the right call here — see what that changes in the cold-climate unit guide.