How we calculate heating costs
Everything on this site comes down to one formula and a handful of published numbers. This page shows all of them so you can check the work or redo it with your own figures.
The formula
Cost per million BTU delivered = price per unit of fuel ÷ (BTU per unit ÷ 1,000,000) ÷ equipment efficiency.
Example: heating oil at $3.70 a gallon, 138,500 BTU per gallon, in a boiler running at 83%: 3.70 ÷ 0.1385 ÷ 0.83 = $32.19 per million BTU delivered.
For heat pumps, "efficiency" is the seasonal coefficient of performance, the units of heat moved per unit of electricity consumed, averaged over a heating season. A value of 2.5 appears as 250%.
Fuel prices
All fuel prices are residential averages from the U.S. Energy Information Administration. Heating oil and propane come from EIA's weekly State Heating Oil and Propane Program survey, which runs October through March and covers the states where those fuels are common; outside the heating season the last reported price is carried forward. Electricity is the monthly average residential price by state from EIA's retail sales data. Natural gas is the monthly residential price by state from EIA's natural gas price summary. Monthly series lag by about two months. Pellet, cordwood and kerosene prices are national defaults that you can edit; EIA doesn't survey them by state.
State averages are averages. Dealer-to-dealer spread in one town can exceed the difference between states, which is why every price on this site is editable.
Heat content
| Fuel | BTU | Unit |
|---|---|---|
| Heating Oil | 138,500 | per gallon |
| Propane | 91,452 | per gallon |
| Natural Gas | 1,036,000 | per Mcf |
| Electricity | 3,412 | per kWh |
| Kerosene | 135,000 | per gallon |
| Pellets | 16,400,000 | per ton |
| Cordwood | 20,000,000 | per cord |
Values are EIA standard conversion factors. Cordwood varies widely by species and moisture, from about 15 to 24 million BTU per cord of seasoned hardwood; 20 is a mid-range figure for mixed northern hardwood.
Equipment efficiency defaults
| Fuel | System assumed | Default |
|---|---|---|
| Heating oil | oil boiler or furnace | 83% |
| Propane | propane furnace or boiler | 90% |
| Natural gas | gas furnace or boiler | 92% |
| Heat pump | cold-climate air-source | 250% |
| Geothermal heat pump | ground-source | 350% |
| Electric resistance | baseboard or space heaters | 100% |
| Wood pellets | pellet stove | 80% |
| Cordwood | EPA wood stove | 70% |
| Kerosene | vented space heater | 85% |
These are typical values for equipment in service, not the best available. A new condensing oil boiler can reach 87%, a condensing gas or propane boiler 95%, and a new cold-climate heat pump a seasonal coefficient above 3.0 in a well-designed system. An older oil boiler can be below 75%. Use your equipment's rated AFUE, or HSPF2 for heat pumps (seasonal COP is roughly HSPF2 ÷ 3.4), and adjust the table.
Duct and pipe losses are not included. A forced-air system with ducts in an unconditioned attic or crawlspace can lose 15 to 25% of its heat before it reaches a room, which affects any ducted system equally and is best treated as a separate problem.
The annual estimate
Annual heat required = heated square feet × annual heating degree days (base 65°F) × an envelope factor in BTU per square foot per degree day: 8 for a drafty older house, 6 for a typical house, 4.5 for a well-insulated one, and 3 for a tight new build. Heating degree days are long-run, population-weighted state values rounded to the nearest hundred; your town may differ by a thousand or more, so for a precise figure use your own fuel history instead.
What's left out
Installed cost, equipment life, rebates and tax credits, maintenance, tank rental, delivery minimums, electricity for pumps and blowers, and the comfort differences between systems. These matter, sometimes more than the fuel, and they are specific enough to your house that a state-level site shouldn't pretend to know them.
Updates
Prices refresh automatically from EIA, weekly during heating season. Last update: 2026-10-24.