Calculations The simplest formula to estimate the amount of energy generated by any electricity generating station is:

(Power x Time) x capacity factor = Energy (electricity) generated The units of energy normally used are megawatt hours (MWh) and kilowatt hours (kWh) but sometimes Joules (J), Kilojoules (kJ) or Mega joules (MJ).

 Power = the rated capacity of the generating station.

 Time = the number of hours in a year

 Capacity factor = an adjustment to take account of the fact that no power station operates at full output all year round.

A wind turbine’s output varies with the wind speed and an average modern wind turbine has a capacity factor of around 30%. This figure should not be confused with the amount of time a wind turbine is generating electricity which is much higher. Worked example for a 2MW (2000kW) wind turbine over a year

 Power = 2000kW

 Time = 24 x 365 = 8760 hours

 Capacity factor = 0.3 (30%)

Energy = (2000 x 8760) x 0.3 = 5,256,000 kWh This amount of electricity is equivalent to that consumed by how many average households? An average household uses 4,700kWh of electricity per year, so… A single 2MW turbine generates an amount of electricity equivalent to that used by approximately…. 5,256,000 / 4,700 = 1118 households