The giant Tesla battery began sending out stored wind power to South Australia's electricity grid a day ahead of schedule due to increasingly hot weather.

The battery was meant to be switched on today, with Premier Jay Weatherill due to visit the site to mark it's official opening on the first day of summer.

But the battery was called on a day early, being put to use on Thursday to meet demand as temperatures across the state hit the mid 30s.

The 100MW/129MWh battery is capable of giving about 30,000 homes electricity for just over an hour.

Tesla claims that the lithium-ion battery has the "largest" storage and is the "most powerful" device of its kind in the world.