AFUE fuel cost calculator

Dollars per delivered MMBtu

AFUE and HSPF2 measure different things in different units, so comparing them directly is meaningless. Convert both to the same figure — what it costs to put one million BTU into the house — and the comparison becomes arithmetic.

gas       $/MMBtu delivered = (price $/Mcf ÷ 1.037) ÷ AFUE
resistance $/MMBtu delivered = ¢/kWh ÷ 100 × 293.1
heat pump  $/MMBtu delivered = ¢/kWh ÷ 100 × 1,000,000 ÷ (HSPF2 × 1,000)

293.1 is simply a million BTU expressed in kilowatt-hours (1,000,000 ÷ 3,412). Electric resistance is 100% efficient at the appliance and still usually the most expensive way to heat, because a kilowatt-hour costs several times what the same energy costs as gas.

Which gas price to use

Residential gas prices swing hard by season, because the meter's fixed monthly charge is spread over a lot of gas in January and almost none in July. The U.S. average for the 2025 heating season was $13.84 per Mcf; the June 2026 figure was $24.09, which is not a heating price at all. Use a winter number, or better, take twelve months off your own bills and divide.

What the numbers usually say

At U.S. average prices, a 96% gas furnace delivers heat for roughly $14 per MMBtu, a heat pump at 8.5 HSPF2 for roughly $22, and resistance strips for roughly $54. Gas wins on running cost in most of the country and loses badly in the places where gas is expensive and power is cheap — the Pacific Northwest, much of the Southeast, anywhere with hydro power.

Change the two price fields to your own and the ranking can flip. That is the point of the tool: the answer is local, and anyone who tells you one fuel always wins has not looked at your bill. The gas against electric comparison adds the install-cost side.

Sources: EIA series N3010US3M, U.S. price of natural gas delivered to residential consumers (released 2026-08-31) (read 2026-09-04) · EIA Electric Power Monthly, Table 5.6.A (released 2026-08-26) (read 2026-09-04) · 10 CFR 430.32(e)(1)(ii)(A) (read 2026-09-04)