kWh, BTU, therms and Calories
Energy shows up in different units depending on who sends the bill: electricity in kilowatt-hours, natural gas in therms (100,000 BTU), furnaces and water heaters in BTU, food in Calories (kcal) and physics in joules.
1 kWh = 3.6 MJ (exact) = 3,412.14163 BTU
1 BTU = 1,055.05585262 J (International Table BTU)
1 therm = 100,000 BTU = 29.30711 kWh
1 kcal = 4,186.8 J → 1 kWh = 859.8452 kcal
kWh conversion table
| kWh | BTU | therm | MJ | kcal |
|---|---|---|---|---|
| 1 kWh | 3,412.1 | 0.034121 | 3.6 | 859.85 |
| 10 kWh | 34,121 | 0.34121 | 36 | 8,598.5 |
| 100 kWh | 341,214 | 3.4121 | 360 | 85,985 |
| 500 kWh | 1,706,071 | 17.061 | 1,800 | 429,923 |
| 1,000 kWh | 3,412,142 | 34.121 | 3,600 | 859,845 |
| 10,000 kWh | 34,121,416 | 341.21 | 36,000 | 8,598,452 |
Worked example: compare a gas bill with an electric one
A gas bill of 50 therms is 50 × 29.3071 = 1,465.4 kWh of heat. A heat pump with a COP of 3 would deliver the same heat with about 488 kWh of electricity.
Food labels use the thermochemical calorie (4.184 J); this converter uses the International Table calorie (4.1868 J). The difference is under 0.1%.
Frequently asked questions
How many BTU are in 1 kWh?
1 kWh = 3,412.14 BTU. Going the other way, 1 BTU = 0.000293 kWh.
How many kWh are in a therm?
1 therm = 100,000 BTU = 29.31 kWh.
Is a food Calorie the same as a kcal?
Yes. A food Calorie (capital C) is 1 kilocalorie, about 4.19 kJ. 1 kWh equals about 860 food Calories.