Back in March, the Tesla founder made a bet on Twitter with Mike Cannon-Brookes, the co-founder of Atlassian, an Australian enterprise software company, that he would be able to install the world’s largest lithium-ion battery in Australia within 100 days, or he would supply it for free. That “free” would have been anything but to Musk, who said failing to meet the deadline would have cost him “$50 million or more,” Business Insider reports.

The 129-megawatt-hour battery was being built by Musk for South Australia, which generates a substantial percentage of its energy from wind power. Musk vowed to install the battery within 100 days of signing as agreement with the state government, which he did in September.

The goal with the battery pack is to make South Australia more self-sufficient and able to provide backup power and affordable energy to South Australians during the summer months.

The battery is part of a $550 million plan by South Australia to help guarantee its power supply after a string of blackouts over the last 18 months. The state has not indicated how much it is paying Musk for the battery. A 250MW gas-fired generator is also expected to come online in the area next summer to help ease energy concerns.

Musk also recently supplied battery power to help aid Puerto Rico’s electrical grid following the devastating hurricane earlier this year.

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