World’s biggest battery installation

JAMESTOWN, Australia—Tesla Inc. Chief Executive Elon Musk may have overpromised on production of the company’s latest electric car, but he is delivering on his audacious Australian battery bet.

An enormous Tesla-built battery system—storing electricity from a new wind farm and capable of supplying 30,000 homes for more than an hour—will be powered up over the coming days, the government of South Australia state said Thursday. Final tests are set to be followed by a street party that Mr. Musk, founder of both Tesla and rocket maker Space Exploration Technologies Corp., or SpaceX, was expected to attend.

Success would fulfill the risky pledge Mr. Musk made in March, to deliver a working system in “100 days from contract signature or it is free.” He was answering a Twitter challenge from Australian IT billionaire and environmentalist Mike Cannon-Brookes to help fix electricity problems in South Australia—which relies heavily on renewable energy—after crippling summer blackouts left 1.7 million people without power, some for weeks.

Mr. Cannon-Brookes then brokered talks between Mr. Musk and Australian Prime Minister Malcolm Turnbull, who has faced criticism from climate groups for winding back renewable-energy policies in favor of coal. South Australia notwithstanding, the country’s per-person greenhouse emissions are among the world’s highest.

South Australia’s government has yet to say how much the battery will cost taxpayers, although renewable-energy experts estimate it at US$50 million. Tesla says the system’s 100-megawatt capacity makes it the world’s largest, tripling the previous record array at Mira Loma in Ontario, Calif., also built by Tesla and U.S. power company Edison.