Last week, the Hornsdale Power Reserve, constructed by Tesla in South Australia, kicked in just 0.14 seconds after a major plant, the Loy Yang station in the neighboring state of Victoria, suffered a sudden drop in output, the International Business Times reports. A week before that, Loy Yang — which operates on coal — was again backed up by Hornsdale within four seconds, a “record” time, state officials said, according to local media reports.

The Hornsdale system uses the same energy-storage technology utilized in Tesla’s electric cars. Its implementation comes on the heels of a March vow from CEO Elon Musk, in which he said Tesla could build and begin operating the system within 100 days from the signature of a contract — or else it would be free. The deal was eventually signed in July with the state of South Australia along with the help of French-based energy company Neoen. On Dec. 1, the Hornsdale reserve was officially turned on.

South Australia has been grappling with rising electricity prices ever since a 2016 storm knocked out the state’s entire power grid, causing 1.7 million residents to temporarily lose their electricity. Storms and heatwaves have resulted in additional blackouts, plunging the region into the midst of an energy crisis.

While its wind turbines can only supply power for short periods, the Hornsdale wind farm is capable of supplying energy to up to 30,000 homes and can act as a last-ditch defense against sweeping power failure.

A spokesperson from Tesla did not immediately respond to a request for comment.