Musk was speaking on SolarCity's conference call on Tuesday when he started talking about the concept of a solar roof, as opposed to a roof with solar modules. With 5 million roofs being added or replaced per year in the US, Musk is eying a large opportunity for SolarCity to jump into the roof-replacement market, as opposed to simply providing panels to go on existing roofs.
"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 added on the call. "So, there is a huge market segment that is currently inaccessible to SolarCity, because people know they're going to have to replace their roof. You don't want to put solar panels on top of a roof you're going to replace."
Musk obviously has interest in SolarCity's growth. Tesla first offered to buy SolarCity in late June, then reached an all-stock buyout agreement last week. Analysts have been skeptical, however, as Tesla has yet to make an annual profit, while SolarCity, which went public in 2012, is burning cash as well. Specifically, SolarCity's 2015 revenue plunged 36 percent to $255 million, while the company took a $375.2 million loss.
Ultimately, Tesla, and Musk in particular, envisions a scenario where Tesla drivers can power their cars off the grid by recharging at homes with SolarCity's panels. Or, as Musk hopes, roofs.