Tesla Inc. (TSLA) has delivered on its promise to build the world’s biggest lithium-ion battery within 100 days.

The company’s Powerpack battery system was switched on to feed Australia’s shaky power grid on Friday, just in time for the summer. CEO Elon Musk, who won the bid to build the 129-megawatt hour battery in July, pledged to have it ready in 100 days or give it away for free. (See also: Elon Musk Says Tesla Can Fix Puerto Rico's Electric Grid.)

The state government-owned battery was described as three times as powerful as any other battery currently installed and capable of powering up 30,000 homes for one hour. It has been hooked up to a wind farm in South Australia. 

South Australia is now leading the world in dispatchable renewable energy, delivered to homes and businesses 24/7. The world’s biggest lithium ion battery. History in the making. @Tesla #cleanenergy #renewables pic.twitter.com/QCDfr1gob4

— Jay Weatherill (@JayWeatherill) 1 December 2017

South Australia generates more than 40 percent of its electricity from wind, leaving it vulnerable to weather patterns. The region has suffered a number of blackouts over the past 18 months. The battery is part of a $385 million energy plan announced last year. Lobby groups said these blackouts cost businesses A$367 million ($278 million), according to the Financial Times.

“The completion of the world’s largest lithium-ion battery in record time shows that a sustainable, effective energy solution is possible,” said Tesla in a statement on Friday.

Tesla’s quick turnaround in building the world’s biggest lithium-ion battery marks an important step for the technology. Proponents believe that batteries can transform the world’s energy systems and help to speed up the adoption of lower-cost solar and wind power solutions.

Australia, like many countries, mainly depends on fossil fuels to power its national grid. South Australia’s state government has sought to address this by promising to provide half of electricity from renewable energy by 2025. However, its efforts have come under fire from critics, who argue that alternative solutions, such as wind power, are unreliable.

Tesla’s massive lithium-ion battery won’t be enough to prevent the region from facing further blackouts, although it does bring more stability to the grid and opens up new possibilities for cleaner tech to be used to power up homes and businesses. Tesla, which hailed its battery as “just the beginning,” according to Reuters, will hope to be at the forefront of providing these solutions. (See also: Tesla Is Counting on Massive Leaps in Technology.)