The Cost Desk

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The outdoor temperature where running costs cross over

Your electricity price, gas price and the unit's efficiency ratings in; the temperature at which a heat pump and a gas furnace cost the same per unit of heat out.

Data last checked . Every source is listed below.

Cents per kilowatt-hour on your bill. The US residential average was 18.16 cents in August 2026 (EIA).

Dollars per therm on your bill. The US residential average of $16.16 per thousand cubic feet in March 2026 is about $1.56 a therm (EIA).

From the unit's spec sheet. Heat delivered per unit of electricity, at 47 °F outside.

Cold-climate models listed by NEEP must reach a COP above 1.75 at 5 °F.

Where running costs cross over

Above about 34 °F the heat pump costs less to run; below it the gas furnace does.

Gas furnace
$16.42 per million Btu95% efficient
Heat pump at 47 °F
$14.04 per million Btu
Heat pump at 17 °F
$21.34 per million Btu
Heat pump at 5 °F
$29.63 per million Btu
Cost of the same heat, by outdoor temperature
$0$20$40$60-10°0°10°20°30°40°50°Outdoor temperature (°F)Crossover
Heat pumpGas furnace

For information only: not advice, a design or a code ruling. We take care, but our sources can lag and so can we, so a figure may be out of date. Package sizes and prices come from the maker and the store, and codes from the local building authority.

What moves the number

The few things that change the answer the most, in plain terms.

The price ratio
The cost of a unit of heat depends on electricity cents per kWh against gas dollars per therm. Where electricity is low-priced or gas is high-priced, the crossover moves colder.
Efficiency falls with the cold
A heat pump delivers less heat per unit of electricity as it gets colder. That is why the pump line in the chart rises toward the left.
Season and demand
Gas and electricity prices both move with the season, fuel markets and demand. The EIA's residential gas price was $16.16 per thousand cubic feet in March 2026 and $27.05 in August 2026, partly because fixed monthly charges are spread over little summer use.
What this leaves out
Equipment and installation cost, capacity at low temperatures, defrost cycles, backup heat, a heat pump's cooling and local rates by time of day are not counted.

The working

Step by step, with the numbers from the starting example, so you can check it on paper.

  1. One therm is 100,000 Btu, so gas at $1.56 a therm costs $15.60 per million Btu of fuel; at 95% efficiency that is $16.42 per million Btu of heat.
  2. One kilowatt-hour is 3,412 Btu, so electricity at 18.2¢ is $53.34 per million Btu of electricity; divided by the pump's efficiency (COP) that is the cost of heat.
  3. COP is 3.8 at 47 °F, 2.5 at 17 °F and 1.8 at 5 °F, joined by straight lines. At 47 °F heat costs $14.04, at 17 °F $21.34, at 5 °F $29.63 per million Btu.
  4. The pump's cost passes the furnace's at about 34 °F.

Try a different case

Each opens the calculator with the numbers filled in.

What we assumed

Where a number is an example, we say so.

  • Checked sourceA therm is 100,000 Btu and a kilowatt-hour is 3,412 Btu. A thousand cubic feet of gas is about 10.36 therms (EIA: 1,036 Btu per cubic foot delivered, 2025).
  • Checked sourceThe default prices are US residential averages from the EIA: 18.16 cents a kWh (August 2026, preliminary) and $16.16 per thousand cubic feet for gas (March 2026, a heating-season month). Your rates and any seasonal or time-of-day rates are what count.
  • Our estimateThe default heat pump ratings (COP 3.8 at 47 °F, 2.5 at 17 °F, 1.8 at 5 °F) are illustrative values for a cold-climate model, not any one product. Manufacturers report COP at those three temperatures. NEEP's cold-climate list requires a COP above 1.75 at 5 °F.
  • Our estimateBelow 5 °F the heat pump's COP continues down the 5 to 17 °F line and never falls below 1. Many units lose capacity or switch to backup heat there.

Sources

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