Heat pump vs oil: the break-even electricity price
A heat pump and an oil boiler cost the same to run when electricity reaches a certain price per kWh for a given oil price. Below that price the heat pump is cheaper to run, above it oil is. The level depends on two numbers you can look up: the oil price per gallon and the heat pump's COP (heat delivered per unit of electricity used). The tables below work it out.
The math
oil: price ÷ (138,500 Btu × boiler efficiency) = $ per Btu delivered
heat pump: price per kWh ÷ (3,412 Btu × COP) = $ per Btu delivered
break-even $ per kWh = oil price × 3,412 × COP ÷ (138,500 × boiler efficiency)
Example with the cost calculator's default values: oil at $5.97 a gallon in an 87% boiler, a heat pump with a COP of 3.15. Break-even is $5.97 × 3,412 × 3.15 ÷ (138,500 × 0.87) = $0.53 per kWh. Read the other way, electricity at $0.26 per kWh matches oil at $2.91 a gallon. The $5.97 oil price is the Maine statewide average as of October 5, 2026 (Maine Department of Energy Resources) and the $0.26 electricity price is Efficiency Maine's default from September 25, 2026. Prices change, so use your own in the table or the calculator.
The heat contents are the U.S. Energy Information Administration's Btu conversion factors (heating oil 138,500 Btu per gallon, electricity 3,412 Btu per kWh). The 87% boiler is Efficiency Maine's default for oil.
Break-even by oil price and COP
Dollars per kWh, for an 87% efficient oil boiler. If you pay less than the number, the heat pump costs less per unit of heat.
| Oil per gallon | COP 2.0 | COP 2.5 | COP 3.0 | COP 3.5 | Calculator |
|---|---|---|---|---|---|
| $4.00 | $0.227 | $0.283 | $0.340 | $0.396 | COP 3.0 row at $4.00 oil |
| $4.50 | $0.255 | $0.319 | $0.382 | $0.446 | COP 3.0 row at $4.50 oil |
| $5.00 | $0.283 | $0.354 | $0.425 | $0.496 | COP 3.0 row at $5.00 oil |
| $5.50 | $0.311 | $0.389 | $0.467 | $0.545 | COP 3.0 row at $5.50 oil |
| $6.00 | $0.340 | $0.425 | $0.510 | $0.595 | COP 3.0 row at $6.00 oil |
| $6.50 | $0.368 | $0.460 | $0.552 | $0.644 | COP 3.0 row at $6.50 oil |
The calculator link fills in that oil price and the break-even electricity price at COP 3.0. The two fuels then show the same cost per million Btu. Change any price there to see the gap move.
An older boiler moves it
The same table at $4.00 a gallon, with different boiler efficiencies. A lower efficiency means more oil per unit of heat, so oil costs more to run and the break-even electricity price falls.
| Boiler efficiency | COP 2.0 | COP 2.5 | COP 3.0 | COP 3.5 |
|---|---|---|---|---|
| 75% | $0.263 | $0.328 | $0.394 | $0.460 |
| 80% | $0.246 | $0.308 | $0.370 | $0.431 |
| 87% | $0.227 | $0.283 | $0.340 | $0.396 |
| 95% | $0.207 | $0.259 | $0.311 | $0.363 |
What changes the answer
- COP in cold weather. The COP on a spec sheet is for one outdoor temperature, and it drops as the air gets colder. NEEP's cold climate specification asks for a COP above 1.75 at 5°F at maximum capacity (NEEP specification), well under the 3.15 seasonal figure used above. Read the left-hand columns of the table as a cold stretch and the right-hand ones as mild weather. For a whole winter, use a seasonal COP.
- Which seasonal COP. PickHVAC calls 2.0 to 3.0 common in cold regions. In a Green Building Advisor thread, a Maine homeowner puts a typical average at 2.5 to 3.0 and January and February closer to 2.0. That is one person's estimate.
- Backup heat. If electric resistance heat switches on below some outdoor temperature, those hours run at a COP of 1.0. Check how your system is set up.
- Prices through the season. Oil is bought by the delivery and the price moves week to week. Electricity is usually a set rate per kWh, and some utilities offer a lower rate for heat pumps.
- What is left out. Equipment, installation, rebates, upkeep and a second system kept as backup. This page compares running cost per unit of heat.
Use your own numbers
Open the heating fuel cost calculator, enter your oil price, your electricity price and a COP you trust, and add the gallons of oil you burn in a season to see the same heat priced in each fuel. To find the gallons, the run-out page turns dated tank readings into a daily rate.
Related
- Heating fuel cost comparison: oil, propane, gas, electric, heat pump, pellets and wood per million Btu.
- Oil and propane tank calculator: dip or gauge reading to gallons.