system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What happens to excess electricity?

When power plants make electricity I assume the always make above what is needed. What the hell happens to the excess that they make? Or if maybe we have a slow day and nobody is using their electricity.

I'm thinking about just every type of powerplant (hydro, nuclear, fossil fuel and steam)
gpt
Nuclear reactor operator here. 

When there is a little more power on the grid than is required, the grid frequency increases, and all devices on the grid use slightly more power to balance this. 

As you have more and more excess power, grid frequency increases and the grid begins to go too fast. Power generators have a "droop" function which starts to reduce the power output of their generators to try and prevent a grid failure. If it gets bad enough then power plants start tripping offline and failing. 

So For small periods of time with small amounts excess power, all the equipment on the grid is forced to accept a little more to balance it, usually this means more heat is dissipated in electronics.