The household
A single-family bungalow in Seattle, WA, roughly 1,400 square feet, currently heated by electric baseboard units room by room — a common setup in postwar Pacific Northwest housing that never needed central air. Cooling has historically been an afterthought here; the home is modeled with a light window-AC-equivalent cooling load. Seattle City Light's residential rate is about 14.95¢/kWh, among the cheaper rates in this case-study set thanks to the region's hydroelectric supply.
The systems
The comparison is a two-zone ductless mini-split (roughly 2.0 tons of combined capacity, installed around $6,750) against replacing the baseboard heaters and adding equivalent cooling capacity in kind (installed around $4,700). Seattle's moderate 4,697 heating degree days and mild winters keep the mini-split's estimated seasonal COP around 2.21 even without cold-climate-rated equipment — standard ductless gear is enough here.
The 10-year math
The heating-energy line does almost all the work in this comparison — cooling barely factors in, since Seattle's 189 cooling degree days are the lowest of any city in this set.
| Cost category | Ductless Mini-Split | Electric Baseboard |
|---|---|---|
| Equipment + install | $6,750 | $4,700 |
| Heating energy (10 yr) | $11,513 | $21,553 |
| Cooling energy (10 yr) | $535 | $569 |
| Maintenance (10 yr) | $1,750 | $1,500 |
| 10-year total | $20,548 | $28,322 |
Electric baseboard heat and a ductless mini-split both run on the same Seattle City Light bill. The only difference is that one of them delivers roughly two units of heat per unit of electricity, and the other delivers exactly one.
The verdict
The heat pump saves an estimated $7,774 over 10 years, driven almost entirely by heating energy — $11,513 versus $21,553 over a decade. Because both systems run on electricity, this comparison isolates the efficiency difference cleanly: it's baseboard's COP of 1.0 against the mini-split's COP of roughly 2.2, with Seattle's cheap hydro-heavy electricity rate benefiting both sides equally.
What could change this
Washington state and many Puget Sound utilities run heat pump rebate programs specifically targeting baseboard-heat conversions — a meaningful incentive here (see the Incentives page) would shorten the payback further. A colder-than-typical Pacific Northwest winter, or a home with a higher-than-typical baseline heating load, would only widen the heat pump's advantage. There's little in this specific matchup that favors sticking with baseboard heat.
Run it with your own numbers
These figures use representative home sizing and each state's EIA-reported energy prices as of August 2026 — see the methodology page for the full model. To see how your actual square footage, equipment, and utility rate change the outcome, run the Heat Pump vs. Traditional HVAC calculator with your own ZIP code.