The two states do not give the same answer. Washington’s 2025 EIA residential averages (13.17¢/kWh and $17.62/Mcf, 1,096 Btu/cf) produce about 16.26/MMBtu for an 8.1 HSPF2 heat pump and 16.92 for a 95% furnace — a slight heat-pump edge at these ratings. Idaho’s electricity is even cheaper (11.83¢/kWh), but its 2025 gas average is only $7.69/Mcf, so the furnace unit cost drops to about 7.79 against 14.60 for the heat pump.
| State | Residential electricity, 2025 (¢/kWh) | Residential gas ($/Mcf) | Implied $/therm | 95% AFUE furnace ($/MMBtu) | 8.1 HSPF2 heat pump ($/MMBtu) |
|---|---|---|---|---|---|
| Washington | 13.17 | 17.62 (2025) | 1.61 | 16.92 | 16.26 |
| Idaho | 11.83 | 7.69 (2025) | 0.74 | 7.79 | 14.60 |
| United States | 17.23 | 15.34 (2025) | 1.48 | 15.59 | 21.27 |
Electricity from EIA Electric Power Annual Table 2.10, 2025 residential, final, retrieved 2026-11-11. Gas and heat content from EIA annual series, release 2026-10-30. Therms per Mcf = heat content (Btu/cf) / 100. Furnace cost = (gas $ per therm × 10) / 0.95. Heat-pump cost = (1,000 / 8.1) × electricity $/kWh. HSPF2 8.1 is ENERGY STAR’s cold-climate minimum for ducted / packaged units, used here as a labeled rating, not a prediction of your climate. State averages are not your tariff.
This is why a national “heat pumps always save money” line fails. Cheap electricity is not enough if gas is cheaper still. These are annual averages, not winter-only tariffs, and HSPF2 remains a Region IV rating. Override the defaults with your bill in the calculator. Dual fuel can still make sense in the coldest weeks even where the seasonal unit cost is close.
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