How these heating costs are worked out
Every number on this site traces back to a published government figure or a physical constant. This page shows the arithmetic, names every source, and states plainly where a figure is a substitute rather than a local reading.
The core formula
Fuels are sold in units that deliver wildly different amounts of heat, and equipment wastes different fractions of it. The only fair comparison is the cost of heat that actually reaches the house, so every fuel is reduced to one figure — dollars per million BTU delivered:
cost per million BTU delivered
= price per unit ÷ (BTU per unit ÷ 1,000,000) ÷ (efficiency ÷ 100)
A worked example
Heating oil in Maine is $5.371 a gallon in the most recent EIA reading. A gallon of No. 2 heating oil holds 138,500 BTU, and a mid-efficiency boiler at 84% AFUE puts 84% of that into the house:
$5.371 ÷ (138,500 ÷ 1,000,000) ÷ 0.84 = $46.17 per million BTU delivered.
The same Maine household on a cold-climate heat pump at COP 2.2, with electricity at 28.63¢ per kWh, pays $38.14 for the same million BTU. Both figures assume the identical amount of heat reaching the same rooms.
Why usage, and not square footage
A square-footage estimate has to guess your insulation, your climate, your windows and your thermostat habits, and each guess compounds. Your own consumption already contains all of them. This site asks what you burned, multiplies by the heat content of that fuel, multiplies by your equipment's efficiency, and treats the result as the heat your house needs. Every alternative is then priced to deliver that same quantity. No climate model is involved, because none is needed.
Efficiency figures
Combustion equipment is quoted as AFUE, the seasonal average including standby and cycling losses. Heat pumps are quoted as seasonal COP rather than nameplate rating, because nameplate is measured at mild temperatures that flatter a machine which will spend the winter working hard. The cold-climate preset of COP 2.2 is a conservative real-world winter average.
Data sources
| Fuel | Source | Latest | Cadence |
|---|---|---|---|
| residential heating oil | EIA — $/gallon | 2026-03-30 | Weekly, October through March only |
| residential propane | EIA — $/gallon | 2026-03-30 | Weekly, October through March only |
| average residential price | EIA — cents/kWh | 2026-05 | Monthly, roughly two months in arrears |
| residential price | EIA — $/Mcf | 2026-05 | Monthly, roughly two months in arrears |
Prices are refreshed automatically from the EIA open-data API. Heating oil and propane are surveyed weekly from October through March only; outside that window the last reading of the season stands and is shown with its date rather than presented as current.
Heat content constants
| Fuel | BTU per unit | Source |
|---|---|---|
| Heating oil (No. 2) | 138,500 / gallon | EIA — 138,500 Btu/gal average heat content, No. 2 distillate |
| Propane | 91,500 / gallon | EIA — 91,500 Btu/gal |
| Natural gas | 1,037,000 / Mcf | EIA — 1,037 Btu/cubic foot average heat content, 2023 |
| Electricity | 3,412 / kWh | 3,412 Btu/kWh — physical constant |
| Wood pellets | 16,500,000 / ton | US DOE / EIA — ~16.5 million Btu per ton, premium grade |
| Cordwood | 20,000,000 / cord | US DOE — ~20 million Btu per cord, seasoned mixed hardwood. Varies widely by species: oak ~24M, pine ~15M. |
| Kerosene | 135,000 / gallon | EIA — 135,000 Btu/gal |
When a state price is not available
EIA does not survey every fuel in every state. Where a local reading does not exist, a substitute is used and always labelled as one — never presented as a state figure. The rules, in order:
- Heating oil — the state reading, or the PADD regional average for that state's region, or the national average. Shown as regional est. or national avg.
- Propane and natural gas — the state reading, or the national average, labelled.
- Electricity — every state and the District of Columbia have a direct reading.
- Wood pellets, cordwood and kerosene — no federal price series exists. These are left out of the comparison entirely until you enter a price. They are never estimated.
Current coverage: heating oil 21 states with a direct reading, propane 38, natural gas 46, electricity 51.
Natural gas units
EIA prices natural gas per thousand cubic feet (Mcf), but US household bills are denominated in therms or CCF. The calculator asks for therms, because that is what is printed on the bill, and converts using the same heat content figure it uses to price the gas — so the conversion cannot disagree with the price. One Mcf is exactly ten CCF; one CCF is roughly one therm.
Residential $/Mcf is inflated in summer months because fixed monthly customer charges are spread over very low volume. For heating comparisons the winter figure is the honest one. Flagged in the UI.
What is deliberately excluded
These comparisons are fuel cost only. They exclude equipment purchase, installation, removal of the old system, maintenance contracts, chimney work, electrical upgrades, delivery minimums, tank rental and the labour of running a wood stove. For most households considering a switch, installation cost decides the question, not the per-BTU figure. Treat the ranking as the running-cost half of a decision, not the whole of it.
Prices are area averages. Your delivered quote will differ, sometimes considerably — rural delivery, contract lock-ins and co-op membership all move it. Every price on this site can be overridden with your own figure, and yours takes precedence.