The next step in Elon Musk’s plan to usher in an era of clean energy starts with replacing your roof with a bunch of solar panels connected to a Tesla battery.

Musk revealed during Solar City’s investor call on Tuesday that Solar City has designed a roof made entirely of solar panels so it can provide solar energy to more people. And, in the process, Musk can also prove it made sense for Tesla to buy Solar City earlier this year.

Solar City estimates that 5 million Americans replace their roofs each year. That’s 5 million people who might consider a “solar roof” that promises to cut their bills and reduce their dependency on non-renewable energy. “If your roof is nearing end-of-life, you definitely don’t want to put solar panels on it, because you’re going to have to replace the roof,” Musk explained on the call with investors. “So, there is a huge market segment that is currently inaccessible to Solar City.”

That could be achieved by using Tesla’s Powerwall to store energy generated by the new solar roof. This could allow homeowners to rely mostly on solar energy instead of having panels installed, trying to make the switch, and discovering that they still have to use the grid whenever it gets dark. Solar City’s technologies will generate the electricity; Tesla’s will find ways to make it more convenient to use.

“Really like solar and battery go together like peanut butter and jelly,” Musk explained on the call. “You obviously need the battery, particularly as you get to scale and you want to have solar be a bigger and bigger percentage of the grid. If you don’t have the batteries there to balance the grid and buffer the power, you really can’t go beyond a certain percentage of solar in a particular neighborhood.”

Musk isn’t the only person who thinks that combination will be the future of solar energy. In January, the U.S. Department of Energy awarded $18 million to six projects that planned to use a combination of solar panels and battery packs to help renewable energy replace fossil fuels.

Solar energy could also help make Tesla’s vehicles more popular. Musk revealed in April that Solar City customers generate enough power to run every Tesla on the road. More solar energy means more Teslas that can run without drawing from the electric grid.

But the biggest shift could be conceptual. Solar power is currently an afterthought — once a house is built and someone’s already connected to the grid, convincing those people to switch to renewable energy gets much harder. Building solar energy right into the roof, however, makes it an integral aspect of the house. To belabor the obvious: Basically, every home has a roof of some kind.

Why not make it a roof that can save people money and help the planet?

Photos via Getty Images / Ralph Orlowski