kWh to BTU Converter

How to convert kilowatt-hours to BTU

A kilowatt-hour is 1,000 watts sustained for one hour, which is 1,000 J/s × 3,600 s = exactly 3,600,000 joules. The British thermal unit began as the heat that warms one pound of water by one degree Fahrenheit, and the International Table BTU now fixes it at exactly 1,055.05585262 J. Dividing gives 3,600,000 ÷ 1,055.05585262 = 3,412.141633 BTU per kWh. The energy converter applies the same joule-based math to calories, kilojoules and foot-pounds.

The trap is confusing energy with power. kWh and BTU are amounts of energy, like gallons of fuel. kW and BTU per hour are rates, like gallons per hour. An air conditioner rated 12,000 BTU/h is a power, and its hourly output is 12,000 BTU of energy. For power ratings use the kW to hp converter or the watts to kW converter.

Step by step

1. Take the energy in kWh from your bill, charger or appliance label.
2. Multiply it by 3,412.1416.
3. Divide by 100,000 if you want therms.
4. Round to the nearest BTU; heating figures rarely need decimals.

See it on a scale

How much heat does a kWh of electricity make?

A kilowatt-hour makes 3,412 BTU of heat in a resistance heater and roughly two to four times that in a heat pump, depending on the heat pump's efficiency and the outdoor temperature.

Every kilowatt-hour sent through a resistance heater, such as a baseboard, a space heater or a furnace's electric strip, becomes exactly 3,412 BTU of heat. That is 100% efficient at the point of use, but no better.

A heat pump moves heat instead of making it. Its coefficient of performance (COP) is the heat delivered divided by the electricity used, both in the same units. A heat pump running at a COP of 3 delivers 3 × 3,412 = 10,236 BTU per kWh. US ratings use HSPF, measured in BTU per watt-hour, so HSPF = COP × 3.412. An HSPF of 8.5 corresponds to an average COP of about 2.49.

Comparing electric and gas heat

To compare a gas furnace with electric heat, convert both to the same unit and include efficiency. One therm burned in a 95% efficient furnace delivers 95,000 BTU of useful heat, which is the same as 27.8 kWh of resistance heat or about 9.3 kWh through a heat pump at COP 3. Multiply those by your own rates to compare costs.

Which BTU is standard, and what does MBH mean?

The International Table BTU (1,055.05585262 J) is the standard in US heating and engineering and the one this converter uses, while MBH means thousands of BTU per hour, as explained below. A thermochemical BTU of about 1,054.35 J appears in some scientific data; with it, 1 kWh would be 3,414.43 BTU, a difference of under 0.07%.

Watch the prefixes in HVAC catalogs. In US practice M means thousand, borrowed from Roman numerals, so MBH is 1,000 BTU per hour and MMBtu is one million BTU. That clashes with the metric M for mega. A boiler rated 100 MBH puts out 100,000 BTU/h, not 100 million.

Gas bills in kWh

In the UK and much of Europe, gas is billed in kWh. The supplier converts the metered volume using the gas calorific value (about 39 to 40 MJ per cubic meter) and a volume correction factor of 1.02264, then divides by 3.6 to get kWh. To compare with a US bill, multiply those kWh by 3,412 for BTU or divide by 29.3071 for therms.

Common mistakes converting kWh to BTU

• Treating BTU/h as BTU. A 5,000 BTU/h window unit does not use 5,000 BTU; it moves that much heat every hour it runs.
• Forgetting efficiency. The fuel table shows energy content, not delivered heat. A 60% efficient oil boiler turns a gallon's 138,500 BTU into about 83,100 BTU of useful heat.
• Dividing instead of multiplying. A BTU is much smaller than a kWh, so the BTU number is always about 3,400 times larger.
• Mixing kW and kWh. A 7 kW heater running for 3 hours uses 21 kWh, which is 71,655 BTU.

Heating quotes often mention temperatures in both scales; the Fahrenheit to Celsius converter handles those. For smaller units of energy, try the joules to calories converter.