Propane Gallons to kWh: The Conversion and What It Means
A gallon of propane holds a fixed amount of energy. Turning that into kilowatt-hours takes one division — but the number that matters for a house is the one after efficiency, and that is where most comparisons go wrong.
The physical conversion from a gallon of propane to kilowatt-hours, plus the efficiency step that decides how much of it your house actually receives.
Converting Propane Gallons to Kilowatt-Hours
Propane is sold by the gallon and electricity by the kilowatt-hour, so any comparison between them has to pass through a common unit first. That unit is the British thermal unit, and the conversion itself is one division. The complication is not the arithmetic. It is that a gallon of propane and a kilowatt-hour of electricity do not deliver the same fraction of their energy to the room, so the raw conversion answers a different question than the one most people are actually asking.
This matters in New York specifically because a large share of the housing stock outside the natural gas service territory heats with delivered fuel. If your fuel arrives on a truck and your heating bill arrives as a delivery ticket rather than a meter reading, converting gallons to kilowatt-hours is the step before you can size anything electric — a heat pump, a solar array, or a budget.
The two numbers the conversion rests on
One gallon of liquid propane holds roughly 91,500 Btu on a higher-heating-value basis. The commonly cited federal figure is 91,452 Btu per gallon, and it is a physical property of the fuel rather than a market number, so it does not move with prices or seasons. It does drift very slightly with temperature, because liquid propane expands as it warms — which is why deliveries are temperature-compensated to a reference of 60 degrees Fahrenheit.
One kilowatt-hour equals 3,412 Btu. That is a definitional conversion between units of energy, exact to the rounding shown.
Gallons to kWh: the arithmetic
Divide the Btu content of the fuel by the Btu content of a kilowatt-hour:
91,452 Btu per gallon ÷ 3,412 Btu per kWh = 26.8 kWh per gallon
So a gallon of propane carries about 26.8 kilowatt-hours of chemical energy. Scale it as needed: a 250 gallon fill is about 6,700 kWh, and 1,000 gallons is about 26,800 kWh, or 26.8 MWh. Going the other way, divide kilowatt-hours by 26.8 to get the equivalent gallons.
Two related conversions people look for at the same time. A therm is defined as 100,000 Btu, which is 29.3 kWh, so a gallon of propane is about 0.91 therm. And a gallon of gasoline is a different fuel with a different figure — the value the EPA uses when it expresses vehicle efficiency in miles per gallon equivalent is 33.7 kWh per gallon, and on a higher-heating-value basis it lands around 35 kWh. Do not use the propane number for gasoline or the other way round.
Weight, litres and other units
The gallon figure is a volume, and propane is often measured by weight instead — cylinders are filled to a weight, not a volume, because a cylinder must keep vapour space above the liquid.
| From | To | Value | Note |
|---|---|---|---|
| 1 US gallon propane | Btu | ≈ 91,500 | Higher heating value, at 60 °F |
| 1 US gallon propane | kWh | ≈ 26.8 | Energy content, before efficiency |
| 1 US gallon propane | pounds | ≈ 4.2 | About 1.9 kg |
| 1 kg propane | kWh | ≈ 14.0 | ≈ 12.9 on a lower-heating-value basis |
| 1 litre propane | kWh | ≈ 7.1 | A US gallon is 3.785 litres |
| 1 therm | kWh | ≈ 29.3 | 100,000 Btu by definition |
| 1 kWh | Btu | 3,412 | Definitional |
| 1 US gallon gasoline | kWh | ≈ 33.7 | The figure behind MPGe; a different fuel |
Note the two propane figures per kilogram. Higher heating value counts the energy recovered when water vapour in the exhaust condenses; lower heating value does not. Appliance efficiency ratings in the United States are quoted against the higher value, so if you are mixing a European datasheet with an American efficiency rating you can build a quiet ten percent error into the comparison.
The step that changes the answer: efficiency
Twenty-six point eight kilowatt-hours per gallon is what the fuel contains, not what the house receives. Between the two sits the appliance.
On the propane side
A propane furnace or boiler is rated by AFUE — the fraction of the fuel’s energy that ends up as usable heat across a heating season, with the rest leaving up the flue and through jacket losses. Modern condensing equipment sits in the mid-nineties; older atmospherically vented equipment sits well below that. Multiply the fuel energy by the rating on the equipment to get delivered heat. At around ninety percent, a gallon delivers roughly 24 kWh of heat into the house.
On the electric side
Resistance heating converts essentially all of its electricity to heat, so a kilowatt-hour in is about a kilowatt-hour of heat out. A heat pump does something different: it moves heat rather than creating it, so it delivers more heat energy than the electrical energy it consumes. The ratio is the coefficient of performance, and it falls as outdoor temperature falls. Averaged over a heating season, a cold-climate system in New York typically operates well above one — which is the entire reason the comparison is not a straight kilowatt-hour swap.
Put together: to match the roughly 24 kWh of heat a gallon of propane delivers, resistance heat needs about 24 kWh of electricity, while a heat pump running at a seasonal coefficient of performance of 2.5 needs about 9.6 kWh. That ratio, not the raw 26.8, is the number to carry into any comparison of running cost or array sizing. It is also why sizing a heat pump alongside solar starts from delivered heat rather than from fuel volume.
Turning it into your own numbers
Fuel prices and utility rates change constantly, vary by region and supplier within New York, and are not something to take from an article. Use your own paperwork instead. The procedure is the same whatever the current figures are:
- Take the price per gallon from your most recent delivery ticket, and divide it by 26.8 to get your cost per kilowatt-hour of propane energy.
- Divide that by your appliance’s efficiency rating to get your cost per kilowatt-hour of delivered heat.
- Take your all-in electricity price from your latest bill — the total charge divided by the kilowatt-hours used, so that delivery and supply are both counted, not just the supply line.
- Divide that by the seasonal coefficient of performance you expect to get your electric cost per kilowatt-hour of delivered heat.
- Compare step 2 against step 4.
Step 3 is where most household comparisons go wrong, because the supply rate printed largest on a bill is not what a kilowatt-hour costs once delivery charges are included. Our walkthrough of reading a utility bill after solar shows where those lines sit and how they interact with credits.
Sizing from annual gallons
If you know how many gallons you burn in a year, you can estimate the annual electricity a heat pump would need for the same job: multiply gallons by 26.8, multiply by the appliance efficiency, then divide by the expected seasonal coefficient of performance. The result is an annual kilowatt-hour figure you can hold against an array’s expected production, or against a service panel’s headroom.
Two cautions. First, a fill is not a year — propane also runs cooking, hot water and sometimes a dryer, and unless you separate those you will size heating against a load that is not all heating. Second, if you are planning to weatherize, do that arithmetic on the improved house, because a tighter shell lowers the load the equipment is sized against. The ordering argument is the same one made in our guide to electrifying a New York home in the right order.
What the conversion does not tell you
It says nothing about capacity. A gallon is a quantity of energy; a heating system also has to deliver enough heat per hour on the coldest morning of the year, and that is a separate calculation. It says nothing about delivery logistics, tank ownership or minimum fill rules. And it says nothing about emissions, which depend on how the electricity was generated, not on the arithmetic. The conversion is a translation between units — a necessary first step, and only a first step.
Frequently Asked Questions
How many kWh are in a gallon of propane?
About 26.8 kWh of chemical energy. A gallon holds roughly 91,500 Btu on a higher-heating-value basis, and one kilowatt-hour is 3,412 Btu, so 91,452 divided by 3,412 gives 26.8. That is the fuel’s energy content, not the heat delivered into a room — the appliance’s efficiency reduces it.
How do I convert kWh back to gallons of propane?
Divide kilowatt-hours by 26.8. So 1,000 kWh is about 37 gallons of propane energy. If you are comparing against heat actually delivered rather than fuel purchased, divide instead by the delivered figure — around 24 kWh per gallon for equipment rated near ninety percent efficient.
How many kWh is a kilogram of propane?
About 14.0 kWh on a higher-heating-value basis, or about 12.9 on a lower-heating-value basis. Propane weighs roughly 4.2 pounds — about 1.9 kg — per US gallon at the 60 degree Fahrenheit reference temperature, which is consistent with the 26.8 kWh per gallon figure.
How many kWh is a litre of propane?
About 7.1 kWh. A US gallon is 3.785 litres, so dividing 26.8 by 3.785 gives the per-litre figure. Note that datasheets outside the United States often quote lower heating value, which runs roughly ten percent below the higher-heating-value numbers used with American appliance efficiency ratings.
Is a gallon of gasoline the same conversion as a gallon of propane?
No. Gasoline is a denser fuel. The figure the EPA uses to express vehicle efficiency in miles per gallon equivalent is 33.7 kWh per gallon, and on a higher-heating-value basis it lands nearer 35. Using the propane number for gasoline understates it by roughly a quarter.
How many MWh are in a full 1,000 gallon propane tank?
About 26.8 MWh of fuel energy, though a tank of that nominal size is normally filled to around eighty percent of its volume to leave vapour space, so a fill is smaller than the tank’s rated capacity. Multiply the gallons actually delivered, which appears on the ticket, rather than the tank’s nameplate size.
Why does efficiency change the comparison so much?
Because the two systems handle energy differently. A propane appliance converts fuel to heat and loses part of it up the flue, so delivered heat is less than the fuel’s energy content. A heat pump moves heat rather than creating it, so it delivers more heat than the electricity it consumes. Comparing raw kilowatt-hours skips both effects and produces an answer that is wrong in opposite directions on each side.
Should I use higher or lower heating value for a home comparison?
Use higher heating value in the United States, because appliance efficiency ratings here are quoted against it. Mixing a lower-heating-value energy figure with a higher-heating-value efficiency rating builds a systematic error of roughly ten percent into the result. Keep both sides of the calculation on the same basis.
NY Solar Incentives
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Run the arithmetic on your own system
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