system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 How an oversupply of solar energy could lead to a blackout

I live in South Australia where 35% of households have solar panels. Some of these panels were temporarily switched off recently in order to avoid a "state wide blackout". How does an excess in energy to the grid cause a blackout?
gpt
Traditional power plants (except hydro) can't switch on/off instantly, it can take hours or days and costs $$. And obviously solar can't generate during the night, so those power plants have to be on and generating at night. But they can't stay on and generating _as well as_ all these solar panels unless there is demand to match the generating capacity (too much energy -> things start tripping to prevent overloads etc., harder to balance) so since the solar panels can be turned off pretty easily, they get shut off first. 

This is why Tesla and their giant batteries is such a big deal: if you can take the excess capacity from wind and solar and store it for use overnight or when its cloudy you _can_ turn off the generating plants and save a whole buncha money.