# Convertisseur d’énergie

> Convertissez kWh en BTU, calories en joules, kcal en kJ et therms en kWh selon les définitions exactes du joule, de la calorie, du BTU et de l’électronvolt.

Version interactive : https://www.calcopenly.com/fr/conversion/energy-converter
Sujet : Convertisseurs d’unités

Every energy unit is a fixed number of joules. A kilowatt-hour is exactly 3.6 MJ (1,000 W for 3,600 s), the thermochemical calorie is 4.184 J, and the International Table British thermal unit is 1,055.05585262 J (NIST SP 811), so each factor is a definition rather than a measurement.

The default converts 1 kWh to 3,412.14 BTU, the link between electricity bills and heating or air-conditioning ratings. Food energy is the other everyday use: a food Calorie is a kilocalorie, so a 2,000 kcal day is 8,368 kJ.

Some units share a name but not a size. The International Table calorie (4.1868 J) is 0.07% larger than the thermochemical one used here, and the US therm (105,480,400 J) is defined with the 59 °F BTU, so it comes to 99,976 International Table BTU rather than 100,000.

## Données

- **Valeur**: Un nombre dans l’unité de départ, ou accompagné de sa propre unité
- **De** (options : joule (J), kilojoule (kJ), megajoule (MJ), watt-hour (Wh), kilowatt-hour (kWh), megawatt-hour (MWh), calorie (cal), kilocalorie (kcal), British thermal unit (BTU), therm (US) (thm), electronvolt (eV), erg, foot-pound (ft·lbf), tonne of oil equivalent (toe))
- **Vers** (options : joule (J), kilojoule (kJ), megajoule (MJ), watt-hour (Wh), kilowatt-hour (kWh), megawatt-hour (MWh), calorie (cal), kilocalorie (kcal), British thermal unit (BTU), therm (US) (thm), electronvolt (eV), erg, foot-pound (ft·lbf), tonne of oil equivalent (toe))

## Résultats

- Valeur convertie — résultat principal
- Conversion
- Facteur de conversion
- Exactitude

## Formule

$$
\begin{gathered} x_{\text{to}} = x_{\text{from}} \times \dfrac{f_{\text{from}}}{f_{\text{to}}} \\ f = \text{one unit expressed in } \text{J} \end{gathered}
$$

## Exemples détaillés

### 1 kWh in BTU

- Valeur: 1 kWh
- De: kilowatt-hour (kWh)
- Vers: British thermal unit (BTU)
- **Valeur convertie: 3,412.14163313 BTU**
- Source de vérification : 3,600,000 J ÷ 1055.05585262 J (International Table BTU, NIST SP 811 App. B) (Python 3.8 fractions from the legal definitions)

### 1 kcal in kJ

- Valeur: 1 kcal
- De: kilocalorie (kcal)
- Vers: kilojoule (kJ)
- **Valeur convertie: 4.184 kJ**
- **Exactitude: Exact**
- Source de vérification : Thermochemical calorie = 4.184 J exactly (NIST SP 811 App. B)

### 1 eV in joules

- Valeur: 1 eV
- De: electronvolt (eV)
- Vers: joule (J)
- **Valeur convertie: 1.602176634 × 10⁻¹⁹ J**
- Source de vérification : e = 1.602176634 × 10⁻¹⁹ C exactly (SI 2019), so 1 eV = 1.602176634 × 10⁻¹⁹ J

### 1 US therm in BTU

- Valeur: 1 thm
- De: therm (US) (thm)
- Vers: British thermal unit (BTU)
- **Valeur convertie: 99,976.1289775 BTU**
- Source de vérification : 105,480,400 J (NIST SP 811 App. B) ÷ 1055.05585262 J (Python 3.8 fractions from the legal definitions)

## Questions

### How many BTU are in a kWh?

3,412.14 BTU. A kWh is 3,600,000 J and the International Table BTU is 1,055.05585262 J, so 3,600,000 ÷ 1,055.05585262 = 3,412.1416. In the other direction 1 BTU is 0.000293071 kWh, so 100,000 BTU of heat is 29.31 kWh.

### How many joules are in a calorie?

4.184 J for the thermochemical calorie used here, or 4.1868 J for the International Table calorie; NIST SP 811 lists both. Nutrition labels count kilocalories, often printed as “Calories”, so one food Calorie is 4,184 J or 4.184 kJ. EU food labels give energy in both kJ and kcal.

### What is a unit of electricity?

One kilowatt-hour, 3.6 MJ: the energy a 1,000 W appliance uses in one hour. Electricity bills in the UK and India count “units” in kWh, so a 2 kW heater running for 3 hours uses 6 units, and a 10 W LED bulb takes 100 hours to use one.

### What is the difference between kW and kWh?

A kilowatt measures power, the rate at which energy is used; a kilowatt-hour measures the energy itself, power multiplied by time. A 3 kW kettle running for 4 minutes uses 3 × 4/60 = 0.2 kWh. Convert kW with the power converter and kWh with this one.

### How many kWh are in a therm?

29.3 kWh. The US therm is 105,480,400 J (NIST SP 811), which is 29.3001 kWh; the EU and UK therm, 100,000 International Table BTU or 105,505,585.262 J, is 29.3071 kWh. The two differ by 0.024%, so either rounds to 29.3 kWh.

### Quelle est la précision de « Convertisseur d’énergie » ?

La précision dépend de vos données et des hypothèses de la méthode. Le calcul décimal utilise 50 chiffres significatifs, mais les estimations, méthodes numériques et données sources peuvent être moins précises ; l’arrondi affiché ne supprime pas ces limites. Exemples résolus vérifiés à partir de sources indépendantes : 4. Par exemple, « 1 kWh in BTU » est vérifié à l’aide de 3,600,000 J ÷ 1055.05585262 J (International Table BTU, NIST SP 811 App. B) (Python 3.8 fractions from the legal definitions).

### D’où vient cette méthode ?

NIST SP 811 (2008), Guide for the Use of the SI, Appendix B — conversion factors; NIST Handbook 44, Appendix C — General tables of units of measurement.

## Sources

- [NIST SP 811 (2008), Guide for the Use of the SI, Appendix B — conversion factors](https://www.nist.gov/pml/special-publication-811)
- [NIST Handbook 44, Appendix C — General tables of units of measurement](https://www.nist.gov/pml/owm/nist-handbook-44-current-edition)