Compare heating fuels by the heat you actually get

Figures checked Nov. 10, 2026

A gallon of propane, a gallon of oil and a cord of wood hold very different amounts of heat. Type in what you pay, and we work out what one million Btu of heat costs from each fuel, after your appliance's efficiency.

The sums behind this tool are tested against 13 worked examples printed in published sources, and 45 checks in all, including the limits where it gives no number.

How the sums work

Each fuel's price is divided by the heat in one unit of it, then by your appliance's efficiency. The answer is the cost of one million Btu of heat that actually reaches your rooms.

Example (a made-up price, not a real one): say you pay $3.00 a gallon for propane, and your furnace is 80% efficient.

One gallon holds 91,452 Btu.
$3.00 ÷ 91,452 × 1,000,000 = about $32.80 per million Btu of fuel.
At 80% efficiency: $3.00 ÷ (91,452 × 0.80) × 1,000,000 = $41.01 per million Btu of heat.

The tool only compares costs. It doesn't show which system suits your home or whether an appliance is installed correctly. Ask a qualified heating professional before changing your heating, and use only the fuel your appliance is made for.

The heat in each fuel

Fuel	Heat	Source
Propane	91,452 Btu per gallon about 91,450; other official tables give 91,300	Official US EIA Monthly Energy Review(opens in a new tab)
Propane, by weight	4.24 lb per gallon used for prices per lb; no government figure found	Other source U-Haul (retailer)(opens in a new tab)
Heating oil (ultra-low-sulfur)	137,381 Btu per gallon up to about 138,500 for higher-sulfur oil	Official US EIA(opens in a new tab)
Kerosene	135,000 Btu per gallon	Official US EIA Monthly Energy Review(opens in a new tab)
Natural gas	100,000 Btu per therm	Official US EIA(opens in a new tab)
Natural gas	1,036 Btu per cubic foot so about 103,600 per ccf	Official US EIA(opens in a new tab)
Electricity	3,412 Btu per kWh	Official US EIA(opens in a new tab)
Wood pellets	16,400,000 Btu per ton (2,000 lb) official range 16.0 to 16.5 million	Official USDA Forest Service(opens in a new tab)
Firewood, average cord	20,000,000 Btu per cord species vary: choose yours in the tool. "Not sure" shows a range, down to the lowest wood figure we hold	Official US EIA(opens in a new tab)

Efficiency figures

You don't need to know your appliance's efficiency. Pick the closest type, such as an older or a high-efficiency furnace, and the tool uses the low end of the official range for it, so costs lean high rather than low. If you know the exact figure from the label (for furnaces and boilers it's called AFUE), you can type it in instead.

Appliance	Efficiency	Source
Furnace or boiler, older	56–70%	Official US DOE Energy Saver(opens in a new tab)
Furnace or boiler, standard (mid-efficiency)	80–83%	Official US DOE Energy Saver(opens in a new tab)
Furnace or boiler, high-efficiency	90–98.5%	Official US DOE Energy Saver(opens in a new tab)
Electric furnace	95–100%	Official US DOE Energy Saver(opens in a new tab)
Electric room heater	100%	Official Missouri DNR Division of Energy(opens in a new tab)
Vented room heaters (examples)	propane 65%; kerosene 80%	Official NYSERDA (New York State Energy Research and Development Authority)(opens in a new tab)
Wood stove, older airtight (average)	55%	Official University of Missouri Extension G5450(opens in a new tab)
Wood stove, newer (non-catalytic to catalytic)	65–83%	Official US DOE Energy Saver(opens in a new tab)
Pellet stove	70–83%	Official US DOE Energy Saver(opens in a new tab)

Before you light it

Carbon monoxide (CO) can kill. US Consumer Product Safety Commission (Official): “Fuel-burning heating systems, including furnaces and fireplaces, can produce CO, an odorless, colorless and deadly gas.” Source(opens in a new tab)
Fit CO alarms and test them. US Consumer Product Safety Commission (Official): “CO alarms should be placed on every level of the home and outside sleeping areas.” “Test the alarms every month to make sure they are working.” Source(opens in a new tab)
Have appliances checked every year. US Centers for Disease Control and Prevention (Official): “Have your heating system, water heater and any other gas, oil, or coal burning appliances serviced by a qualified technician every year.” Source(opens in a new tab)
Chimneys and vents too. US Fire Administration (Official): “Have chimneys and vents cleaned and inspected at least once a year.” Source(opens in a new tab)
If a CO alarm sounds (US: call 911): US Centers for Disease Control and Prevention (Official): “If the detector sounds leave your home immediately and call 911.” Source(opens in a new tab)
Know the signs. US Centers for Disease Control and Prevention (Official): “The most common symptoms of CO poisoning are headache, dizziness, weakness, nausea, vomiting, chest pain, and confusion.” Source(opens in a new tab)
Carbon monoxide (CO). CPSC (Official): "Fuel-burning heating systems, including furnaces and fireplaces, can produce CO, an odorless, colorless and deadly gas." "CO alarms should be placed on every level of the home and outside sleeping areas." Source(opens in a new tab)

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Sources for this page

17 figures, each with its source

Every figure on this page, with its source. Open one to see the exact words on the source page and how it was checked.

High-efficiency furnaces and boilers (AFUE): 90–98.5% Official
From US DOE Energy Saver: Furnaces and Boilers (read via energy.gov/node/374305), which says: “90% to 98.5% AFUE.” Open the source (opens in a new tab)
Checked Nov. 9, 2026. A second check re-opened the source page and matched it on Nov. 9, 2026.
Mid-efficiency furnaces and boilers (AFUE): 80–83% Official
From US DOE Energy Saver: Furnaces and Boilers (read via energy.gov/node/374305), which says: “80% to 83% AFUE.” Open the source (opens in a new tab)
Checked Nov. 9, 2026. A second check re-opened the source page and matched it on Nov. 9, 2026.
Older, low-efficiency furnaces and boilers (AFUE): 56–70% Official
From US DOE Energy Saver: Furnaces and Boilers (read via energy.gov/node/374305), which says: “older fossil fuel furnace and boiler systems have efficiencies in the range of 56% to 70%” Open the source (opens in a new tab)
Checked Nov. 9, 2026.
All-electric furnace or boiler (AFUE): 95–100% Official
From US DOE Energy Saver: Furnaces and Boilers (read via energy.gov/node/374305), which says: “The AFUE rating for an all-electric furnace or boiler is between 95% and 100%.” Open the source (opens in a new tab)
Checked Nov. 9, 2026. A second check re-opened the source page and matched it on Nov. 9, 2026.
Electric resistance space heaters: 100% Official
From Missouri DNR Division of Energy: Space Heaters PUB2849 (04/01/2020), which says: “All electric resistance heaters are considered 100% efficient because there is no heat loss through ducts or combustion.” Open the source (opens in a new tab)
Checked Nov. 9, 2026. A second check re-opened the source page and matched it on Nov. 9, 2026.
Heat content of a kilowatthour: 3,412 Btu per kWh Official
From US EIA: Units and calculators explained, British thermal units (Btu), which says: “1 kilowatthour=3,412 Btu” Open the source (opens in a new tab)
Checked Nov. 9, 2026. A second check re-opened the source page and matched it on Nov. 9, 2026. A blind check looked it up again on Nov. 10, 2026 without seeing our figure: the two agreed.
Heat content of a cord of wood (generic, species not known): 20,000,000 Btu per cord Official
From US EIA: Units and calculators explained, British thermal units (Btu), which says: “1 cord=20,000,000 Btu” Open the source (opens in a new tab)
Checked Nov. 9, 2026. A second check re-opened the source page and matched it on Nov. 9, 2026. A blind check looked it up again on Nov. 10, 2026 without seeing our figure: the two agreed.
Heat content of heating oil (No. 2 / ultra-low-sulfur): 137,381 Btu per gallon Official
From US EIA: Energy conversion calculators (2026 estimates), which says: “1 gallon=137,381 Btu” Open the source (opens in a new tab)
Checked Nov. 10, 2026. A second check re-opened the source page and matched it on Nov. 9, 2026. A blind check looked it up again on Nov. 10, 2026 without seeing our figure: it didn't find a better source, so this figure stands.
Heat content of kerosene: 135,000 Btu per gallon Official
From US EIA Monthly Energy Review, Sept 2026, Appendix A Table A1, which says: “Kerosene 5.670” Open the source (opens in a new tab)
Checked Nov. 9, 2026. A second check re-opened the source page and matched it on Nov. 9, 2026. A blind check looked it up again on Nov. 10, 2026 without seeing our figure: the two agreed.
Heat content of natural gas: 1,036 Btu per cubic foot Official
From US EIA: Energy conversion calculators (2026 estimates), which says: “1 cubic foot=1,036 Btu” Open the source (opens in a new tab)
Checked Nov. 10, 2026. A blind check looked it up again on Nov. 10, 2026 without seeing our figure: it found that our figure or its wording needed correcting, and the corrected version is the one shown.
Heat content of a therm: 100,000 Btu per therm Official
From US EIA: Units and calculators explained, British thermal units (Btu), which says: “1 therm=100,000 Btu” Open the source (opens in a new tab)
Checked Nov. 9, 2026. A second check re-opened the source page and matched it on Nov. 9, 2026. A blind check looked it up again on Nov. 10, 2026 without seeing our figure: the two agreed.
Pellet stoves (efficiency): 70–83% Official
From US DOE Energy Saver: Wood and Pellet Heating, which says: “Pellet stoves that are certified by the EPA are likely to be in the 70% to 83% efficiency range.” Open the source (opens in a new tab)
Checked Nov. 9, 2026. A second check re-opened the source page and matched it on Nov. 9, 2026.
Heat content of wood pellets: 16,400,000 Btu per ton (2,000 lb) Official
From USDA Forest Service, Forest Products Laboratory: Fuel Value Calculator (updated July 2004), hosted by Nebraska Energy Office, which says: “Wood pellets (premium) | ton | 16,400,000 | 13,600,000 | 83%” Open the source (opens in a new tab)
Checked Nov. 10, 2026. A second check re-opened the source page and matched it on Nov. 9, 2026. A blind check looked it up again on Nov. 10, 2026 without seeing our figure: each was partly right, and the figure shown is the one settled after comparing both.
Heat content of propane: 91,452 Btu per gallon Official
From US EIA Monthly Energy Review, Sept 2026, Appendix A Table A1 (Approximate Heat Content of Petroleum and Biofuels), which says: “Propane 3.841” Open the source (opens in a new tab)
Checked Nov. 10, 2026. A blind check looked it up again on Nov. 10, 2026 without seeing our figure: it found that our figure or its wording needed correcting, and the corrected version is the one shown.
Weight of a gallon of propane: 4.24 pounds per gallon Other source
From U-Haul (retailer): 20-lb Steel Propane Tank product page (answer in the page's customer Q&A, 2021), which says: “The Propane that should be going into this tank only would weigh about 4.24lbs per gallon of propane.” Open the source (opens in a new tab)
Checked Nov. 10, 2026. A second check re-opened the source page and matched it on Nov. 9, 2026. A blind check looked it up again on Nov. 10, 2026 without seeing our figure: it didn't find a better source, so this figure stands.
Vented fuel room heaters (efficiency examples): propane 65%; kerosene 80% Official
From NYSERDA (New York State Energy Research and Development Authority): Compare Heating Fuels, which says: “| | | | | | Room Heater (Vented) | AFUE | 65.0 | 65% | $54.74 | $4.16 ; Kerosene | Gallon | $3.81 | 135,000 | $28.22 | Room Heater (Vented) | Estimate | 80.0 | 80% | $35.28 | $2.68” Open the source (opens in a new tab)
Checked Nov. 9, 2026. A second check re-opened the source page and matched it on Nov. 9, 2026.
Wood stoves (efficiency): 65–83% (HHV) Official
From US DOE Energy Saver: Wood and Pellet Heating, which says: “New advanced non-catalytic combustion stoves often have efficiencies of 65% to 75%, HHV.” Open the source (opens in a new tab)
Checked Nov. 9, 2026. A second check re-opened the source page and matched it on Nov. 9, 2026.