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).
What is watt hour?
A watt hour is a unit of energy equal to the power of one watt sustained for one hour. It is used to measure small amounts of electrical energy consumption, particularly in battery capacities and portable electronics.
Real-world uses
Watt-hours measure the energy stored in or consumed from batteries, small electronics, and portable power stations. A smartphone battery holds roughly 10–15 Wh; a laptop battery 40–100 Wh. Solar panel output for small installations is often quoted in Wh per day.
History
The watt-hour emerged as a practical energy unit in the late 19th century with the commercialisation of electric power distribution. It offered a convenient scale between the joule (too small) and kilowatt-hour (too large) for everyday portable energy applications.
Common mistakes
Confusing watt-hours (energy) with watts (power). A device rated at 5 W running for 3 hours consumes 15 Wh. Also, treating Wh and mAh as interchangeable without knowing voltage: Wh = mAh × V ÷ 1000.
When is this conversion used?
Converting between therm (US) and watt 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.
Worked examples
1 therm (US) = 29,307.22222222 watt hour
1 watt hour = 3,600 joule
How to convert therm (US) to watt hour
To convert therm (US) to watt hour, multiply the value by 29,307.22222222.
To convert watt hour back to therm (US), multiply by 0.00003412.
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: therm (US) to watt hour
| therm (US) | watt hour |
|---|---|
| 0.1 | 2,930.72222222 |
| 0.5 | 14,653.61111111 |
| 1 | 29,307.22222222 |
| 2 | 58,614.44444444 |
| 5 | 146,536.11111111 |
| 10 | 293,072.22222222 |
| 25 | 732,680.55555556 |
| 50 | 1,465,361.11111111 |
| 100 | 2,930,722.22222222 |
| 250 | 7,326,805.55555556 |
| 500 | 14,653,611.11111111 |
| 1,000 | 29,307,222.22222222 |
Common values
| therm (US) | watt hour | |
|---|---|---|
| A food calorie (1 kcal) | 0.00003966 therm (US) | 1.16222222 watt hour |
| A AA battery | 0.00008872 therm (US) | 2.6 watt hour |
| Boiling a kettle | 0.00398082 therm (US) | 116.66666667 watt hour |
| Daily human diet (2000 kcal) | 0.07931302 therm (US) | 2,324.44444444 watt hour |
| 1 gallon of gasoline | 1.24883893 therm (US) | 36,600 watt hour |
Available Energy units
More therm (US) conversions
- Convert therm (US) to joule
- Convert therm (US) to kilojoule
- Convert therm (US) to kilowatt hour
- Convert therm (US) to calorie (thermochemical)
- Convert therm (US) to kilocalorie (dietary)
- Convert therm (US) to watt hour
- Convert therm (US) to megajoule
- Convert therm (US) to electronvolt
- Convert therm (US) to British thermal unit
Assumption: calorie means thermochemical calorie, and therm means US therm.