Tesla is about to switch on the world’s largest lithium-ion battery. The 100-megawatt battery will be a back up for the power grid serving Southern Australia.

The battery was commissioned after a storm led to a blackout in September 2016. Around 1.7 million people lost power after officials shut down supplies across the state; had they not done so, it was likely the knock-on effect could have taken the blackout nationwide.

While the storm was the inspiration, the Tesla battery is designed more to deal with fluctuations in demand that lead to what are known as load shedding blackouts. This is where local demand exceeds the current supply on the grid and power has to be cut to avoid damaging the grid itself.

The battery will be charged and maintained from a wind farm. It should have the capacity to power around 30,000 homes for one hour.

Tesla chief Elon Musk will likely be relieved with the completion of the battery and installation. He’d made a wager on Twitter that the project would be complete within 100 days or he would waive the cost, which some estimates put as high as US$50 million. He did mitigate the risk somewhat by stipulating that the 100 days ran from when the contract was signed, by which point the construction was roughly half-completed.