Power efficiency

The efficiency of a power system varies by power source and this measurement is called capacity factor. Nuclear is 92%, Wind is 35% and Solar is 25%. The big difference is that the wind doesn't always blow and the sun doesn't always shine. This is called curtailment. Wind and solar need a back up system but nuclear does not. Also if a nuclear plant shuts down you are saving on fuel cost but this is not the case when wind and solar shut down.