Which run on those evil fossil fuels, the same as the ones which fuel power plants.
How about just using the power plants to begin with? I have a sneaking suspicion that regular use of an efficient power plant even year round, would use less energy than a generator would to make up for green energy short falls.
Nuclear power generating plants should be up and running before any gas/coal generating plants are closed.
Wind and solar 'ain't' going to do it.