Fuels are sold in different units, so a gallon of propane and a therm of gas are hard to compare. This calculator converts every fuel to the same thing: the cost of one million BTU of heat actually delivered into your home.
Cost of heat, cheapest first
Yearly cost for your heat use
| Fuel | $ per MMBtu delivered | Per year |
|---|
Energy content of heating fuels
| Fuel | Sold by | Heat per unit | Typical efficiency |
|---|---|---|---|
| Natural gas | therm | 100,000 BTU | 80–97% (AFUE) |
| Propane | gallon | 91,500 BTU | 80–95% |
| Heating oil | gallon | 138,500 BTU | 80–87% |
| Electric resistance | kWh | 3,412 BTU | 100% |
| Heat pump | kWh | 3,412 BTU | 200–350% (COP 2–3.5) |
| Wood pellets | ton | 16.4 million BTU | about 80% |
| Firewood (hardwood) | cord | about 20 million BTU | 60–75% (EPA stove) |
Cost per million BTU delivered = price per unit ÷ (million BTU per unit × efficiency)
Example: propane vs heat pump
At $2.80 a gallon, propane in a 92% furnace costs $2.80 ÷ (0.0915 × 0.92) = about $33 per million BTU. Electricity at 17 cents in a heat pump with a seasonal COP of 2.6 costs $0.17 ÷ (0.003412 × 2.6) = about $19 per million BTU. For a home that uses 60 million BTU a winter, that is roughly $2,000 against $1,150.
How much heat does my house use?
The best source is last winter’s bills. Multiply the therms of gas you used by 0.1, gallons of propane by 0.0915, or gallons of oil by 0.1385, then multiply by your furnace efficiency. The result is million BTU delivered. If you don’t have bills, the heat pump savings calculator estimates it from your square footage and climate.
Where to find your prices
- Electricity and gas: divide the total on your bill (including delivery charges) by the kWh or therms used.
- Propane and oil: use the price per gallon on your last delivery ticket.