Surplus electricity

At every moment in time, electricity generation has to be carefully balanced against electricity consumption. Renewables can sometimes generate too much electricity that has nowhere to go. File:electricity-supply-demand-curves.png

Sources

Solar

If rooftop solar panels were commonplace, there would be surplus electricity during the day.

Wind

In some cases, there is surplus electricity during peak winds.

Hydro

Even though hydropower capacity stays the same 24/7, electricity demand still varies with the time of day. Outside of peak hours, there may be surplus electricity.

Geothermal

Only a few parts of the world can generate electricity from geothermal energy. Some of those places may be "in the middle of nowhere" with not a lot of people around.

Nuclear

Some power plants can't be ramped up or ramped down to match the changing demand - they have to operate at the same level 24/7. So like hydropower, there may be surplus electricity outside of peak hours.

Uses

Surplus electricity could be used to generate hydrogen gas, which could be used as a fuel.