Elon Musk’s SpaceX committed to spending over $2.8 billion in recent months to buy gas turbines to power data centers for its artificial intelligence unit, the company revealed in a regulatory filing on Wednesday.

The relatively large investment shows that Musk is continuing to double down on gas turbines, even after SpaceX’s use of them prompted public complaints, a lawsuit, and regulatory inquiries into whether the company may be polluting the air with carbon emissions and dodging environmental requirements.

A shortage of electricity is the leading constraint on an otherwise roaring data center boom happening across the US. Portable gas turbines—generators that can run without drawing power from the grid—have been viewed as quick and temporary solutions until more robust sources of energy come online.

In addition to launching rockets and selling satellite internet, SpaceX also owns Musk’s xAI unit, which develops Grok. To support the chatbot and other AI efforts, xAI operates a pair of data centers known as Colossus 1 in Memphis, Tennessee, and Colossus 2 in Southaven, Mississippi. SpaceX is leasing access to some of the servers at the Colossus data centers for $15 billion annually to Anthropic, the AI startup that develops the Claude chatbot. Musk said on Wednesday that SpaceX plans to sign additional deals.

The new details about SpaceX’s energy spending are part of a wave of disclosures in the company’s prospectus for its initial public offering, a lengthy document that is designed to help potential investors understand the company’s financial health and long-term risks. SpaceX is aiming to debut on the Nasdaq stock exchange in the coming weeks.

In March, SpaceX agreed to buy $805 million worth of turbines from an unnamed company through 2029, according to the IPO filing. Then, in late April, Musk’s company struck a deal for $2 billion worth of mobile gas turbines and related items from an unnamed vendor. That deal is still pending.

Last week, WIRED reported that 19 new portable turbines had been added to Colossus 2 over the past two months, for a total of 46 units. Portable turbines can be operated without a clean air permit for a year, a rule that SpaceX has used in its favor. Some of the turbines were added after the NAACP and other advocacy groups sued xAI, alleging that the company had been operating 27 gas turbines without appropriate permits, posing a risk to public health and the climate.

As of March, SpaceX had enough servers between the two data centers to use about 1 gigawatt of power, which is about as much electricity as is used by a large US city. But the company expects to keep growing, which will increase its power needs. SpaceX has more than $14 billion in construction in progress, including the value of data center equipment that’s not yet operational, according to Wednesday’s filing.