Energy & costs
Comparing gas, propane, oil, electric and heat pumps per million BTU
Therms, gallons, kWh and tons do not compare directly. Turn each into dollars per million BTU of heat delivered and the cheapest fuel is obvious.
The common unit
Every heating fuel is sold in its own unit: gas by the therm or hundred cubic feet, propane and oil by the gallon, electricity by the kWh, pellets by the ton and firewood by the cord. To compare them, convert each price into the cost of one million BTU of heat delivered to the house. That needs the fuel’s energy content, from the US Energy Information Administration (EIA), and the efficiency of the equipment that burns it:
The fuel cost per million BTU calculator does this for every fuel at once.
Energy content and default prices
| Fuel | Unit | BTU per unit | Default price | Default efficiency | Cost per million BTU delivered |
|---|---|---|---|---|---|
| Natural gas | therm | 100,000 | $1.50 | 95% | $15.79 |
| Heat pump | kWh | 3,412 | $0.17 | COP 2.8 | $17.79 |
| Cordwood | cord | 20 million | $300 | 70% | $21.43 |
| Wood pellets | ton | 16.5 million | $300 | 80% | $22.73 |
| Propane | gallon | 91,452 | $2.70 | 95% | $31.08 |
| Heating oil | gallon | 138,500 | $3.70 | 85% | $31.43 |
| Electric resistance | kWh | 3,412 | $0.17 | 100% | $49.82 |
The default prices are rounded US residential averages from EIA data for 2025. They vary a great deal by state and by month, so enter your own from a recent bill; the method matters more than the defaults. The full table, with sources, is on the fuel energy content and cost reference.
What the table says
At average prices, gas and a heat pump are close, and both are about half the cost of propane and oil. Electric resistance heat, in baseboard heaters, electric furnaces and heat pump backup strips, is the most expensive by far, about three times the cost of gas or a heat pump. That is the arithmetic behind replacing electric baseboard with a heat pump in any climate, and behind keeping a heat pump off its strips as much as possible, as the guide to heat pumps in cold climates explains.
The break-even electricity price
For a household with gas, the key question is at what electricity price a heat pump beats the furnace:
At $1.50 gas, a COP of 2.8 and a 95% furnace, the break-even is 15.1 cents per kWh. A household paying less than that for electricity heats more cheaply with the heat pump; one paying more heats more cheaply with gas. A simpler rule, close enough for most cases: the break-even in cents is about 3.6 times the gas price per therm times the COP.
Gas billed per CCF and cheap hydro power
Gas at $1.40 per CCF (103,700 BTU) in a 95% furnace, electricity at $0.12 per kWh, a heat pump at COP 3.2.
- Heat pump: $0.12 ÷ 3,412 × 1,000,000 ÷ 3.2 = $10.99 per million BTU
- Gas: $1.40 ÷ 103,700 × 1,000,000 ÷ 0.95 = $14.21 per million BTU
- Electric resistance: $35.17 per million BTU
With cheap electricity and a good heat pump, the heat pump is the cheapest heat by almost a third. A CCF holds 3.7% more energy than a therm, which matters when comparing a CCF price with a therm price.
From cost per BTU to a season’s bill
Cost per million BTU ranks the fuels; the season’s heat sets the size of the bill. The heating cost by fuel calculator multiplies one by the other for a house’s design load and climate. For a zone 5 house with a 60,000 BTU per hour design load, 84.2 million BTU a season, it gives $1,330 for gas, $1,499 for a heat pump at COP 2.8, $2,618 for propane, $2,648 for oil and $4,197 for electric resistance. The guide to degree days explains how the season’s heat is estimated.
The heat pump’s real COP
A heat pump’s COP is not fixed. It is highest in mild weather and falls in cold weather, and below the balance point backup heat at a COP of 1 takes over part of the load. A seasonal COP of 2.8 is reasonable for a modern heat pump in a mixed climate; in a cold climate the effective seasonal figure, including backup, can be nearer 2.2 to 2.5. The heat pump versus furnace cost calculator includes the backup share for that reason. In its zone 5 example, a 10% backup share brings the effective COP down to 2.37 and the furnace saves $439 a season; in a propane house in a milder climate, the heat pump saves $870 a season.
Efficiency ratings feed in directly
The efficiency in the formula is the equipment’s seasonal rating: AFUE for furnaces and boilers, and the seasonal COP, HSPF2 ÷ 3.412, for heat pumps. A higher rating lowers the cost per million BTU in direct proportion, which the guide to efficiency ratings covers. An old 80% furnace raises the gas cost to $18.75 per million BTU at $1.50 a therm, enough to tip the comparison toward a heat pump at many electricity prices.
Beyond the fuel price
Running cost is only part of the comparison. Installation costs differ, gas and propane need venting and a gas line, oil needs a tank, and a heat pump also replaces the air conditioner. A gas connection carries a fixed monthly customer charge whether gas is used or not, which matters for a household thinking of dropping gas entirely. And fuel prices move: oil and propane have the most volatile prices, electricity the least.