Billionaire Elon Musk has been using a Tesla subsidiary to build a giant battery that will be connected to Texas' creaking power grid.

It comes days after a mid-February storm temporarily knocked out around half the state's generating plants, triggering outages that killed dozens and pushed power prices up to 10 times the normal rate.

The previously unrevealed energy storage project by Gambit Energy Storage LLC will have a capacity of 100 megawatts, according to a report by Bloomberg - enough to power around 20,000 homes on a hot summer day.

Utility-scale batteries are needed to store the electricity produced by wind and solar, but they can also become lucrative opportunities. By storing excess electricity when prices and demand are low, battery owners can sell it back to the grid when prices are high.

Property records on file with Brazoria County show Gambit shares the same address as a Tesla facility near the company’s auto plant in Fremont, California.

The battery-storage system being built by Tesla’s Gambit subsidiary is registered with the Electric Reliability Council of Texas (Ercot).

Warren Lasher, senior director of system planning at Ercot, said the project has a proposed commercial operation date of June 1.

The move marks Tesla’s first major foray into the epicentre of the US energy economy.

While Tesla is best known for producing battery-powered electric vehicles, the company has spent years expanding the Tesla Energy arm of the business.

Musk and his executive team continue to highlight energy as a key part of their growth. “I think long-term Tesla Energy will be roughly the same size as Tesla Automotive,” Musk said during an earnings call in July 2020. “The energy business is collectively bigger than the automotive business.”

At the time of its launch in 2017, Tesla's battery project in South Australia was the largest in the world at 100 megawatts.

Set up adjacent to a wind farm, it could store surplus electricity generated on windy nights for daytime demand.

“Tesla’s energy storage business on a percentage basis is growing faster than their car business, and it’s only going to accelerate,” said Daniel Finn-Foley, head of energy storage at Wood MacKenzie Power and Renewables.

“They are absolutely respected as a player, and they are competing aggressively on price.”

Tesla's latest energy project is based in Angleton, Texas, a town of roughly 3,000 people, around 40 miles south of Houston.

However the project remains shrouded in secrecy. A photographer who attempted to observe from the front gate was told by a worker that it was a “secretive project" and white sheets obscured what appeared to be Tesla’s modular Megapacks.