Average load factors
Historically the average load factor availability of pressurised water reactors world-wide over the past 40 years has been 75%, meaning that on average a typical PWR reactor will generate 75% of its maximum electrical capacity each year. Electricity companies today operate pressurised water reactors much more efficiently, achieving an 83% average load factor world-wide in 2009.
Modern Generation III+ nuclear reactor designs are expected to reach operational load factors of greater than 90%. Maintenance and refuelling outages are very carefully planned in advance so that down-time is minimised and the reactor can resume electricity generation as fast as possible. This is important to earn money for the utility from electricity sales and pay-off interest from the reactor build cost. Older nuclear reactor designs are far less efficient. Britain's Generation I Magnox nuclear power stations have achieved an average load factor of 57% over their lifetime. The Magnox fleet has operated at just over half of its maximum capacity.