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The Hornsdale Power Reserve: The Tesla “Big Battery” and Elon Musk's Wager

Updated: Oct 26, 2023

In early 2017 the South Australian government had been facing a major power supply crisis with South Australian residents having suffered multiple blackouts. In March of 2017, the head of Tesla’s battery division, Lyndon Rive, offered to solve South Australia’s power crisis, stating that an installation of batteries for reserve power could be completed within 100 days. Elon Musk then made a promise to the South Australian government that the system would be “installed and working 100 days from contract signature or it is free.”

The Hornsdale Power Reserve, also known as the "Tesla Big Battery," at sunset next to Elon Musk viewing the battery isntallation from above. The Text "Elon's "Big Battery"" is foregrounded.

The contract for the project was signed on September 29th and construction was completed 45 days ahead of schedule. Removing weekends, the battery installation was in fact completed exactly 99 days after Mr. Musk made the initial wager.

Mr. Musk made good on his promise and in December of 2017 the Hornsdale Power Reserve, dubbed the “Tesla Big Battery” and the world’s largest lithium-ion battery at the time, was turned on.

The installation is co-located alongside the Hornsdale WInd Farm and both systems are owned by Neoen. The “Mega-battery” has 129 megawatt-hours of energy storage and 100 megawatts of generation capacity. This translates to being capable of powering 30,000 homes for eight hours or 60,000 homes for four hours.

The battery system is designed to store energy from renewable sources, such as wind and solar power. It can then release this energy back into the grid when needed, helping to stabilise the grid and reduce the need for fossil fuels. Costings for the project were not initially made public but were released in September of 2018. The total cost of the project was $90 million, in line with expectations.

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