Energy Glossary

## Kilowatt Hour (kWh)

The kilowatt hour is used as energy unit. It is defined as

1 kilowatt hour = (the power of 1 kilowatt) x (1 hour duration)

#### Understanding the meaning of 1 kilowatt hour

A horse can deliver a (more or less) permanent power of 1 hourse power which is equivalent to 0.735 kilowatts. A horse delivers during 1.35 hours the amount of 1 kilowatt hour in terms of mechanical energy:

(1 horse power) x (1.35 hours) =

(0.75 kilowatt) x (1.35 hours) = ca. 1 kilowatt hour

(0.75 kilowatt) x (1.35 hours) = ca. 1 kilowatt hour

Please observe that the kilowatt hour means kilowatt multiplicated by hour!

#### Usage

The kilowatt hour is mainly used to measure electric energy (= power, electricity) but can be used to describe the amount of energy for each type of energy.

As comparison a seleced list of fuels with their specific energy content is listet below.

Fuel/energy carrier | Energy in kWh | Energy in Joule |
---|---|---|

1 cubic meter nat. gas | 10 | 36 000 000 |

1 litre of gas or diesel | 10 | 36 000 000 |

1 kg of hydrogen | 33 | 100 000 000 |

1 kg of dry wood | 5 | 18 000 000 |

1 kg rechargeable lithium ion battery | 0.1-0.3 | 330 000 - 1 000 000 |

1 metric ton of water in hoover dam (200m) | 0.5 | 2 000 000 |

IMPORTANT NOTICE: The given values in the table are rough values and might depend on fuel quality etc.