What is kilowatt hour?
A kilowatt hour is a unit of energy equal to 1,000 watt hours. It is the standard billing unit used by electricity providers worldwide to measure household and commercial energy consumption.
Real-world uses
The kilowatt-hour is the standard unit for electricity billing worldwide. A typical household uses 250–1,000 kWh per month. EV charging, home appliance energy consumption, and solar panel production are all expressed in kWh. Utility bills list total kWh consumed and price per kWh.
History
The kilowatt-hour became the standard billing unit for electricity in the early 20th century as public electricity grids were established. Its use is mandated for utility metering in most countries. It equals exactly 3,600,000 joules (3.6 MJ).
Common mistakes
Writing "kW/h" instead of "kWh"—the slash implies division (kW per hour), which is a rate of power change, not an energy unit. Also confusing kWh with kW: a 2 kW heater running for 4 hours uses 8 kWh of energy, not 8 kW.
What is therm (US)?
A US therm is a unit of energy equal to 100,000 BTU. It is used by gas utility companies in the United States as the standard billing unit for natural gas consumption.
Real-world uses
The therm is used in the United States and United Kingdom for natural gas billing. One therm equals 100,000 BTU (approximately 29.3 kWh). Residential gas bills in the US often list consumption in therms. It is also used in industrial gas metering and procurement contracts.
History
The therm was introduced as a practical unit for natural gas billing in the early 20th century, when gas supply companies needed a convenient large-scale energy unit for residential and commercial customers. It consolidated prior inconsistent measurement practices in the gas industry.
Common mistakes
Confusing the therm with the BTU—1 therm = 100,000 BTU. Also, the US therm and the UK therm differ slightly (the UK therm is based on 105.5 MJ, while the US therm is exactly 100,000 BTU ≈ 105.48 MJ). Not to be confused with the thermie (a metric unit of heat).
When is this conversion used?
Converting between kilowatt hour and therm (US) is common when working across metric and imperial systems, such as international trade, travel between countries with different measurement standards, or following instructions from a different region. Electricity bills use kilowatt-hours while physics calculations use joules. Converting between them is essential for energy audits, comparing appliance efficiency, and understanding power consumption.
Worked examples
1 kilowatt hour = 0.03412128 therm (US)
1 therm (US) = 105,506,000 joule
How to convert kilowatt hour to therm (US)
To convert kilowatt hour to therm (US), multiply the value by 0.03412128.
To convert therm (US) back to kilowatt hour, multiply by 29.30722222.
Measurement standards
The joule is the SI derived unit of energy, defined as one kilogram-metre-squared per second-squared (kg·m²/s²). The kilowatt-hour, equal to exactly 3.6 megajoules, is accepted for use with the SI by the BIPM for practical electricity metering.
Did you know?
A single bolt of lightning releases roughly 1 to 5 gigajoules of energy, yet only a small fraction reaches the ground as electrical current. Most of the energy dissipates as light, heat, and the thunder shockwave.
Quick reference: kilowatt hour to therm (US)
| kilowatt hour | therm (US) |
|---|---|
| 0.1 | 0.00341213 |
| 0.5 | 0.01706064 |
| 1 | 0.03412128 |
| 2 | 0.06824256 |
| 5 | 0.17060641 |
| 10 | 0.34121282 |
| 25 | 0.85303206 |
| 50 | 1.70606411 |
| 100 | 3.41212822 |
| 250 | 8.53032055 |
| 500 | 17.0606411 |
| 1,000 | 34.1212822 |
Common values
| kilowatt hour | therm (US) | |
|---|---|---|
| A food calorie (1 kcal) | 0.00116222 kilowatt hour | 0.00003966 therm (US) |
| A AA battery | 0.0026 kilowatt hour | 0.00008872 therm (US) |
| Boiling a kettle | 0.11666667 kilowatt hour | 0.00398082 therm (US) |
| Daily human diet (2000 kcal) | 2.32444444 kilowatt hour | 0.07931302 therm (US) |
| 1 gallon of gasoline | 36.6 kilowatt hour | 1.24883893 therm (US) |
Available Energy units
More kilowatt hour conversions
- Convert kilowatt hour to joule
- Convert kilowatt hour to kilojoule
- Convert kilowatt hour to calorie (thermochemical)
- Convert kilowatt hour to kilocalorie (dietary)
- Convert kilowatt hour to watt hour
- Convert kilowatt hour to megajoule
- Convert kilowatt hour to electronvolt
- Convert kilowatt hour to British thermal unit
- Convert kilowatt hour to therm (US)
Assumption: calorie means thermochemical calorie, and therm means US therm.