system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:What happens to the excess electricity produced by a power plant?
gpt
They normally sell it to other power companies that need it, they can store a small amount of it (with some loss) by pumping water upwards at a hydro dam to let it fall back down later.

Mostly though they are really good at knowing how much power people will use, because people as a whole are really predictable, so they tend to be pretty close.