The unit of power is a watt (W), which is defined as the consumption of one joule of energy per second.
1 Kilowatt (KW) = 1,000 W
1 Megawatt = 1,000 KW = 1 million W
1 Gigawatt = 1,000 MW = 1 million KW = 1 billion W
1 Terawatt = 1,000 GW = 1 million MW = 1 billion KW = 1 trillion W
A watt is a measure of capacity for a power station—how much energy it can produce in one hour. In the case of nuclear power stations, this is the electrical energy produced (excess heat energy is not measured, as it is not used).
Output of power stations is measured in watt-hours. This is equal to its output over the whole year. A power station with a capacity of 1MW would produce 8,760MWh of energy over a year, if it produced energy non-stop.
The average household in the Great Britain used 3,954KWh in 2014, down from 4,602KWh in 2005—in Wales it was a little lower, around 3,735KWh in 2014. The total UK electricity consumption was 295,320GWh in 2014 and total Welsh consumption was 16,451GWh.
166 Department for Energy and Climate Change, , accessed 22 June 2016
21 July 2016