kWh to BTU Calculator

How to use the kWh to BTU calculator

Enter an amount of energy in kilowatt-hours and you get the same energy expressed in BTU. That is the whole job: one number in, one number out, with nothing personal in between. There is no rate here and no dollars, because this is a straight physical conversion — a kilowatt-hour and a BTU are two ways of measuring the exact same quantity of energy, the way a metre and a foot are two ways of measuring the same distance. The default of 1 kWh is there so you can see the conversion factor straight away before swapping in your own figure. Because the factor is a definition rather than a measurement, the answer carries no uncertainty at all; the only rounding anywhere in the result is the rounding the display does.

The point of the tool is to be a bridge between two worlds that rarely speak the same language. On one side is the electric world — your meter, your bill, and appliances rated in kilowatt-hours — where energy is counted in kWh. On the other is the heating and cooling world — furnaces, air conditioners, water heaters, and gas appliances — where the same energy is quoted in BTU, in therms of 100,000 BTU, or in millions of BTU. When a spec sheet hands you one unit and your bill speaks the other, this converter lets you compare them on a single scale instead of guessing. It is also the first step in almost every honest fuel comparison, because you cannot weigh gas against electricity until both sit on one ruler.

A BTU, or British Thermal Unit, is roughly the energy it takes to raise one pound of water by one degree Fahrenheit. It is a small unit — there are 3,412.14 of them in a single kilowatt-hour — which is why heating and cooling specs run into the thousands and tens of thousands. Keep one distinction clear, because it is the mistake that costs people the most: this tool converts an amount of energy, not a rate. HVAC equipment is normally rated in BTU per hour, meaning energy moved every hour it runs, and that is a different quantity from a plain BTU figure. Multiply a BTU per hour rating by the hours it actually runs before you treat it as an amount.

Read the output as a plain restatement, never as an estimate. Convert a kilowatt-hour your meter recorded into BTU and you have the identical energy on the heating side of the fence; there is no efficiency, no loss, and no price folded in, because none of those belong in a unit conversion. For a quick sanity check on the gas side, remember that a therm is exactly 100,000 BTU, so one kilowatt-hour is about 0.0341 therms and a month of 900 kWh is about 30.7 therms of raw energy. If you want to size cooling in BTU per hour for a room instead, the btu-calculator works from the dimensions of the room; if you want water heating in particular, the water-heating-cost-calculator carries the same physics into a practical figure.

The formula

A kilowatt-hour and a BTU both measure energy, so converting between them is a single fixed multiplication — there is no rate to enter and nothing to estimate, just the constant that links the two units. What makes this conversion unusual among the ones people meet in daily life is that the constant is derived from definitions on both sides rather than from any measurement, so it carries no tolerance and no uncertainty.

A kilowatt-hour is one kilowatt sustained for one hour, which is 3,600,000 joules exactly. The BTU used in energy statistics is the international-table BTU, fixed at 1,055.05585262 joules. Divide the first by the second and you get 3,412.14, the number this tool multiplies by. The Energy Information Administration publishes the same relationship rounded to 3,412 BTU per kWh, so a difference in the fourth significant figure between an official table and this tool is rounding, not disagreement.

BTU = kWh × 3412.14
kWh = BTU ÷ 3412.14   (the reverse)
1 kWh = 3,600,000 J ÷ 1,055.05585262 J per BTU = 3,412.14 BTU
therms = BTU ÷ 100,000 = kWh × 0.0341214

Worked example with the default of 1 kWh: 1 × 3,412.14 = 3,412.14 BTU. The conversion is perfectly linear, so it scales without any correction — 5 kWh × 3,412.14 = 17,060.7 BTU, 0.5 kWh × 3,412.14 = 1,706.07 BTU, and a 900 kWh month, which is an ordinary household total, comes to 900 × 3,412.14 = 3,070,926 BTU. Divide that last figure by 100,000 and the same month of electricity is 30.71 therms of raw energy, which is the number you would compare against a gas bill.

That therm bridge is the practical reason this conversion matters. A therm is defined as exactly 100,000 BTU, and a ccf of natural gas — 100 cubic feet — carries about 103,600 BTU at the US average heat content of 1,036 BTU per cubic foot that EIA estimated for 2026, which works out to about 1.036 therms per ccf. So one ccf of gas holds roughly 30.36 kWh of raw energy. Heat content genuinely varies with the gas your supplier delivers, which is why your bill prints its own therm factor and why treating a ccf as exactly one therm is only a rough approximation.

One caveat outranks every other on this page: a BTU is an amount of energy, and BTU per hour is a rate. An air conditioner labelled 10,000 BTU is telling you how much heat it can move in an hour, not how much energy it will use, and a furnace labelled 60,000 BTU is quoting an hourly input rate. Converting either of those ratings straight into kWh gives you the energy for one hour of running and nothing more. To size cooling from the dimensions of a room, use the btu-calculator; to turn a rating into a running cost, work out the actual electrical draw first and take that into the electricity-cost-calculator.

Frequently asked questions