Heat pump vs furnace cost

Cheapest way to heat a house: cost per million Btu

The fair way to compare heating systems is the cost of one million Btu (MMBtu) of heat delivered into the house: fuel price ÷ energy per unit ÷ efficiency. Energy per unit is 100,000 Btu per therm of gas, 91,452 per gallon of propane, 138,500 per gallon of heating oil and 3,412 per kWh.^[btu] A heat pump's HSPF2 is Btu of heat per watt-hour, so HSPF2 7.5 means 7,500 Btu per kWh, a seasonal coefficient of performance (COP) of 7,500 ÷ 3,412 = 2.2.^[cfr430]

• Gas furnace: $ per therm × 10 ÷ AFUE
• Propane furnace: $ per gallon × 10.93 ÷ AFUE
• Oil furnace or boiler: $ per gallon × 7.22 ÷ AFUE
• Heat pump: $ per kWh × 1,000,000 ÷ (HSPF2 × 1,000)
• Electric baseboard: $ per kWh × 293.1

Worked example. 600 therms in a 95% furnace deliver 57.0 MMBtu. At the U.S. averages that heat costs $946.80 with gas and $1,371.04 with a HSPF2 7.5 heat pump at 18.04¢ per kWh.^{[ngprice][eia861m]}

Heat pump vs gas furnace cost by state

At each state's 12-month average prices, a minimum-efficiency heat pump is cheaper to run than a 95% gas furnace in 9 states and costlier in 42. The heat pump wins where electricity is cheap or gas is expensive, such as Hawaii, Florida, Arkansas, Louisiana; gas wins by the widest margin in Alaska, California, New York, Maine.^{[eia861m][ngprice][ngheat]}

A higher-efficiency heat pump moves the line: at HSPF2 9 the heat pump's cost per MMBtu falls by one-sixth. Prices are averages; the calculator above takes your own.

Propane and oil vs heat pump

Where there is no gas line the comparison is easier. At this week's U.S. averages, propane in a 95% furnace costs $32.53 per MMBtu and oil in an 85% system $50.24, against $24.05 for a heat pump.^{[shopp_lp][shopp_oil]} Weekly fuel prices by state are on propane prices and heating oil prices.

What the comparison leaves out

• Cold-weather performance. HSPF2 is a seasonal test rating. Cold climates need heat pumps designed to run at lower outdoor temperatures before switching to resistance heat; enter a lower HSPF2 to test a standard model in a cold state.^[femp]
• Furnace standards. New non-weatherized gas furnaces must reach 80% AFUE today and 95% from December 18, 2028; new oil furnaces 83%.^[cfr430]
• Cooling. A heat pump also replaces the air conditioner, which a furnace does not.
• Equipment and installation cost, ductwork, maintenance and the life left in your current system.
• Your real rates. Some utilities offer lower winter or heat pump rates; your tariff's marginal price per kWh is what matters.

For the yearly electricity a heat pump uses, including cooling, see heat pump cost; for the gas side, the average gas bill by state.