Watt hours - the consumption and production of energy is often measured in watt hours. If a 40-watt light bulb is lit for an hour, 40 watt hours of electric power is used.

The power consumption of a household is normally measured in kilowatt hours (kWh, a thousand watt hours).

The energy consumption in Norway is measured in gigawatt hours (GWh, a billion watt hours) or terawatt hours (TWh, a thousand billion watt hours).

Joule is another unit of measurement for energy. 1 kWh equates to 3.6 million joule (=3.6 MJ)

Prefixes:
k = kilo = 10³
M = mega = 10⁶
G = giga = 10⁹
T = tera = 10¹²
P = peta = 10¹⁵