Cost per million BTU delivered = price per unit / (BTU per unit x efficiency) x 1,000,000. With EIA heat contents and typical efficiencies, the cheapest fuel depends almost entirely on your local prices; enter yours in the calculator.
Why fuels need one yardstick
Cordwood is sold by the cord, pellets by the ton or bag, natural gas by the therm or thousand cubic feet, propane by the gallon and electricity by the kilowatt-hour. The only fair comparison is the cost of the heat each delivers into the room, which needs two numbers per fuel: its heat content and the efficiency of the appliance burning it.
EIA publishes heat contents: a cord of wood 20,000,000 BTU, a gallon of propane 91,452 BTU, a cubic foot of natural gas 1,036 BTU and a kilowatt-hour 3,412 BTU. The USDA Forest Products Laboratory's fuel value table pairs fuels with typical efficiencies and gives premium pellets 16.4 million BTU per ton. That table notes it was developed with boilers in mind, so use your own heater's efficiency where the maker states it.
A worked comparison
| Fuel | Heat content | Efficiency used | Example price | Cost per million BTU |
|---|---|---|---|---|
| Seasoned cordwood | 20,000,000 BTU per cord | 77% | $300 per cord | $19.48 |
| Wood pellets | 16,400,000 BTU per ton | 83% | $350 per ton | $25.71 |
| Natural gas | 1,036,000 BTU per thousand cubic feet | 80% | $14 per thousand cubic feet | $16.84 |
| Propane | 91,452 BTU per gallon | 79% | $3.00 per gallon | $41.52 |
| Electricity | 3,412 BTU per kWh | 100% | $0.18 per kWh | $53.22 |
Electricity and natural gas prices are EIA US residential averages (18.16 cents per kWh in August 2026; $13.96 per thousand cubic feet in January 2026). The cordwood, pellet and propane prices are round examples, not market data; local prices vary widely, and that variation decides the ranking. Our fuel cost calculator runs the same formula on your prices and your heater's efficiency.
The formula, step by step
Take pellets at $350 a ton: 16,400,000 BTU per ton times 83% efficiency is 13,612,000 BTU delivered. $350 divided by 13.612 million BTU is about $25.71 per million BTU. Electricity at 18.16 cents per kWh: one million BTU is 293 kWh at 3,412 BTU each, and 293 x $0.1816 is about $53.22. Electric resistance heat delivers all of its energy into the room, so no efficiency loss applies.
A vent-free gas appliance keeps nearly all its heat in the room, so its effective efficiency is higher than the 80% used for natural gas above; a vented log set loses most of its heat up the chimney, so its effective efficiency is far lower. Adjust the efficiency to the appliance, not just the fuel.
What the number leaves out
- Appliance and installation cost: a pellet stove, chimney liner or gas line can outweigh years of fuel savings.
- Your time: cutting, splitting, stacking and loading cordwood is labour the price doesn't show.
- Electricity used by pellet stove augers and fans, and by blowers on any stove.
- Seasonal price swings: propane and pellets often cost more in mid-winter.
Using it to choose a heater
If two fuels come out close at your prices, choose on convenience and outage resilience. Wood keeps you warm in a power cut; pellets offer thermostat control; gas is hands-off; electric needs no venting at all. Our guides to wood vs pellet stoves and electric fireplace heat cover those trade-offs.