SpaceX is known for putting rockets into orbit. Lately, it is also known for buying a lot of Tesla batteries.
The buying is ramping up fast. In the first three months of the year, xAI spent just $34 million on Tesla's Megapacks, the giant battery packs Tesla makes for storing power.
Then came the second quarter. The earnings report, released Tuesday, put Megapack purchases at $295 million and brought the 2026 total to $329 million.
The tie goes back to one person. Musk is SpaceX's chief executive and largest shareholder, and he also heads Tesla.
The batteries are most likely going to xAI's data centers. SpaceX absorbed xAI earlier this year, after xAI bought the social platform X in 2025.
xAI was already a big customer before the merger. It had bought $430 million in Megapacks for its data centers on its own.
That history matters. The earlier orders show the demand did not appear out of nowhere after the merger.
AI data centers do not sip power at a steady rate. Their needs swing with the work being done at any given moment.
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Training a model, when the AI learns from massive piles of data, is a huge power draw. So is inference, the moment when the AI gives you an answer.
Those swings can set off expensive utility charges or overload the generators on site. Megapacks flatten the spikes, which cuts costs and keeps the center running.
The packs can push power back in a second or less. That is fast enough to protect the GPUs, the computer chips doing all the heavy AI math, during demand surges.
xAI has leaned mainly on natural gas for its data-center power. Many of those natural gas turbines at a Mississippi site near the Colossus project are unpermitted.
Even so, the Megapacks matter. They catch sudden demand spikes before the site can pull gas power online.
For a facility that never wants to shut down, that speed counts. It buys time when gas turbines cannot react quickly.
The Tesla-SpaceX shopping list does not stop at batteries.
So money is flowing between Musk's companies in several directions at once. For Tesla shareholders, that is real revenue.
The deals also raise a fair question. When the buyer and the seller answer to the same person, are the sales numbers showing genuine demand or just internal reshuffling?
There is even a Wall Street name for this setup: a related-party transaction. It just means the two sides of the deal are connected by more than normal business.
For investors, the useful takeaway is that energy storage has become central to the AI buildout. Data centers need power that can surge in an instant, and Megapacks are built for exactly that.
That does not mean every order between Musk's companies is a sign of true customer demand. It means the batteries are filling a real need, and the companies supplying them are in a strong spot while the AI boom goes on.
The story of AI is not just about chips. It is also about the batteries that keep them running, and the companies in that corner of the market are seeing the demand show up in their numbers.
For investors, that makes the energy side of the AI boom as worth watching as the software side.
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