Elon Musk is consolidating: Tesla and SolarCity joined forces Monday just a few days after shareholders approved the all-stock acquisition. The deal values SolarCity at $2 billion, and now that it’s finished, Musk can keep working to prove that the companies belong with each other.

Tesla’s planned acquisition of SolarCity was announced in June. Musk said at the time that he had “zero doubt about this” and that “arguably we should have done it sooner.” His plan was for SolarCity to make solar products that would store any excess energy in batteries manufactured by Tesla. It seemed like a win-win proposition. On Monday, it was made official.

Musk’s reiterated his belief in August when Tesla and SolarCity teased a solar roof and Musk described the companies as peanut butter and jelly. Yet the companies’ shareholders weren’t convinced, which put the deal’s future in question.

Still, the companies kept working together, and revealed new solar roof tiles — which just so happened to be called the Tesla Glass Tile — in October. Then, in November, Musk revealed that the solar roof would cost less than a normal roof.

Shareholders finally voted to approve the deal on November 17 — even though Musk, who owns 20 percent of Tesla’s stock, opted not to vote because he wanted other investors to feel heard. Now that the deal has closed, it wouldn’t be a surprise to see the companies work on products like the solar roof that complement their missions.

That’s all part of Tesla’s shift in focus toward promoting clean energy instead of only working on electric vehicles. But prospective Tesla owners need not fret — buying SolarCity could help Tesla by making its vehicles easier to charge.

Musk has said all along that this was a win-win. With the support of the companies’ shareholders and the deal’s closure, he now has the chance to prove that a futuristic roof isn’t the only way Tesla will use its new foothold in the solar energy market. Peanut butter and jelly are great together, and nobody spends $2 billion in stock to make one sandwich.

Photos via Getty Images / Bill Pugliano