Does anybody know…?

I’m starting to wonder something about electrical power usage and generation in general. Let’s pretend everybody was able to cut their power usage by 10%. This would translate into savings for individual users and businesses; but would the total energy usage by the power company to generate the electricity change all that much? Do all the turbines still have to be turning when at 70% capacity as much as they are at 80% capacity; or do some shut off or turn on depending on load? If they do all have to be turning, are they using more or less the same amount of oil or coal to keep running?
The question is, does 10% less energy usage on the consumer end translate into 10% less total generation on the supplier end?