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 electronvolt?
An electronvolt is a unit of energy equal to the work done on an electron by a potential difference of one volt, approximately 1.602 × 10⁻¹⁹ joules. It is used in atomic physics, particle physics, and quantum mechanics.
Real-world uses
The electronvolt is the standard energy unit in particle physics, atomic physics, and semiconductor science. X-ray photon energies are measured in keV; visible light photons in eV (about 1.8–3.1 eV); nuclear reactions in MeV; and particle accelerator energies in GeV or TeV.
History
The electronvolt came into use in the early 20th century with the development of quantum mechanics and experimental atomic physics. As physicists began measuring energies of electrons and photons, the eV provided a convenient unit far smaller than the joule but appropriate for subatomic-scale phenomena.
Common mistakes
Confusing the electronvolt with a unit of voltage—it is a unit of energy equal to the kinetic energy gained by one electron accelerated through a potential difference of one volt (1 eV = 1.602 × 10⁻¹⁹ J). Also mixing up the scale prefixes (keV, MeV, GeV, TeV) when discussing different physical phenomena.
When is this conversion used?
Converting British thermal unit to electronvolt is useful in the energy domain when comparing values across different measurement standards or applying formulas that require a specific unit.
Worked examples
1 British thermal unit = 6.585141e+21 electronvolt
1 electronvolt = 1.602177e-19 joule
How to convert British thermal unit to electronvolt
To convert British thermal unit to electronvolt, multiply the value by 6.585141e+21.
To convert electronvolt back to British thermal unit, multiply by 1.518570e-22.
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 electronvolt
| British thermal unit | electronvolt |
|---|---|
| 0.1 | 6.585141e+20 |
| 0.5 | 3.292570e+21 |
| 1 | 6.585141e+21 |
| 2 | 1.317028e+22 |
| 5 | 3.292570e+22 |
| 10 | 6.585141e+22 |
| 25 | 1.646285e+23 |
| 50 | 3.292570e+23 |
| 100 | 6.585141e+23 |
| 250 | 1.646285e+24 |
| 500 | 3.292570e+24 |
| 1,000 | 6.585141e+24 |
Common values
| British thermal unit | electronvolt | |
|---|---|---|
| A food calorie (1 kcal) | 3.96566683 British thermal unit | 2.611447e+22 electronvolt |
| A AA battery | 8.87156825 British thermal unit | 5.842052e+22 electronvolt |
| Boiling a kettle | 398.08319053 British thermal unit | 2.621434e+24 electronvolt |
| Daily human diet (2000 kcal) | 7,931.33366278 British thermal unit | 5.222895e+25 electronvolt |
| 1 gallon of gasoline | 124,884.38377248 British thermal unit | 8.223812e+26 electronvolt |
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.