What is British thermal unit?
A British thermal unit (BTU) is an energy unit defined as the heat needed to raise one pound of water by one degree Fahrenheit. It is used in HVAC systems, heating and cooling equipment ratings, and natural gas billing in the United States.
Real-world uses
The British Thermal Unit is used in the United States for heating and cooling system ratings (furnaces, air conditioners), natural gas billing, and refrigeration. A typical home air conditioner might be rated at 12,000–24,000 BTU/h. Natural gas is often sold per therm (100,000 BTU).
History
The British Thermal Unit was proposed in the 1840s as the heat needed to raise one pound of water by one degree Fahrenheit. Despite its name, its primary use today is in the United States; the UK and most Commonwealth countries have transitioned to SI units for engineering applications.
Common mistakes
Confusing BTU (energy) with BTU/h (power). An air conditioner rated at "12,000 BTU" typically means 12,000 BTU per hour of heat removal capacity, not a fixed energy amount. Also mixing up the slightly different BTU definitions (IT, thermochemical, 39°F, 60°F).
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.
When is this conversion used?
Converting between British thermal unit and kilowatt hour 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 British thermal unit = 0.00029307 kilowatt hour
1 kilowatt hour = 3,600,000 joule
How to convert British thermal unit to kilowatt hour
To convert British thermal unit to kilowatt hour, multiply the value by 0.00029307.
To convert kilowatt hour back to British thermal unit, multiply by 3,412.14163313.
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: British thermal unit to kilowatt hour
| British thermal unit | kilowatt hour |
|---|---|
| 0.1 | 0.00002931 |
| 0.5 | 0.00014654 |
| 1 | 0.00029307 |
| 2 | 0.00058614 |
| 5 | 0.00146536 |
| 10 | 0.00293071 |
| 25 | 0.00732678 |
| 50 | 0.01465355 |
| 100 | 0.02930711 |
| 250 | 0.07326777 |
| 500 | 0.14653554 |
| 1,000 | 0.29307107 |
Common values
| British thermal unit | kilowatt hour | |
|---|---|---|
| A food calorie (1 kcal) | 3.96566683 British thermal unit | 0.00116222 kilowatt hour |
| A AA battery | 8.87156825 British thermal unit | 0.0026 kilowatt hour |
| Boiling a kettle | 398.08319053 British thermal unit | 0.11666667 kilowatt hour |
| Daily human diet (2000 kcal) | 7,931.33366278 British thermal unit | 2.32444444 kilowatt hour |
| 1 gallon of gasoline | 124,884.38377248 British thermal unit | 36.6 kilowatt hour |
Available Energy units
More British thermal unit conversions
- Convert British thermal unit to joule
- Convert British thermal unit to kilojoule
- Convert British thermal unit to kilowatt hour
- Convert British thermal unit to calorie (thermochemical)
- Convert British thermal unit to kilocalorie (dietary)
- Convert British thermal unit to watt hour
- Convert British thermal unit to megajoule
- Convert British thermal unit to electronvolt
- Convert British thermal unit to therm (US)
Assumption: calorie means thermochemical calorie, and therm means US therm.