South Australian Premier Jay Weatherill listens as Tesla chief executive Elon Musk announces at a ceremony in Adelaide that Tesla will install the world’s largest grid-scale battery in Australia. (Ben MacMahon)

Elon Musk just made an expensive wager: He will build the world’s largest lithium battery in just 100 days or he’ll pay for the whole project.

Musk’s electric car company Tesla announced Friday that it won the bid to build the battery in the Australian state of South Australia in an agreement that includes Neoen, a French renewable energy provider, and the South Australian government.

The idea started in March when Musk said Tesla could deliver an operational battery-powered system to the state and that he would begin the 100-day countdown once the official agreement was signed.

In September, South Australia suffered significant infrastructure damage after a storm caused a statewide blackout and left 1.7 million citizens without electricity. Further blackouts occurred earlier this year in the heat of the Australian summer.

Tesla’s 100MW/129MWh battery will partner with Neoen’s Hornsdale wind farm, which is north of South Australia, putting Australia at the center of global energy storage technology according to BusinessInsider.

Musk, who was in South Australia for the announcement, said that the 100-day rule will be included in the official contract because “that’s what we publicly said we were going to do.”

He added that the total cost of the project will be released at the country’s discretion.

Musk tweeted Friday that the project is breaking new ground for renewable energy and that the battery will be three times as powerful as its nearest competitor.

In a statement on its website, Tesla said the project should be completed by December and will be able to power more than 30,000 homes.

At the announcement, Musk said that, depending upon the energy level that marks the end of its life, the battery could last up to 15 years. The electronics for the system can last 20 to 30 years, he said.

Tesla says the battery will be running constantly and will provide stability services for renewable energy and be available for emergency backup power if an energy shortfall is predicted.

Tesla is also set to release its Model 3 car on Friday, the company’s first affordable, pure-electric car.