While Tesla Energy has continued to sell the traditional solar panels SolarCity used to install — which are made by third-party manufacturers such as Trina Solar — it has brought two new products to market since the acquisition.
The first was its Powerwall storage battery, designed to store energy generated by a customer's solar system so even if the power goes down in their neighbourhood they'll have access to power.
It's not entirely clear whether development on the Powerwall began before or after the acquisition. Tesla gave a preview of the storage battery at an event in May 2015, but in testimony on Tuesday Musk said development of the Powerwall was "beginning" when the acquisition happened in 2016.
"We were beginning development of the Tesla Powerwall battery. And in order to have a compelling product, you really needed to have a tightly integrated solar and battery solution. And we could not create a well-integrated product if SolarCity was a separate company," Musk told the court.
The second is the Solar Roof, which instead of bolting panels on top of a customer's roof replaces the entire roof with photovoltaic shingles.
Musk debuted the Solar Roof in October 2016 during a glitzy event on a house from the show "Desperate Housewives."
"It needs to be beautiful, affordable and seamlessly integrated," Musk said at the unveiling event, adding: "You'll want to call your neighbors over and say, 'check out this sweet roof.'"
Depositions from Tesla executives later revealed the tiles Musk had shown off at the event hadn't been operational.
Tesla did not start actually installing Solar Roof until 2019. In a deposition, Musk said this was because Tesla had to divert resources away from Tesla Energy to focus on the Model 3 production ramp.