Still, SolarCity and its ilk face formidable challenges. It is trying to outrun rivals in a race to transform the power industry. Utilities are furiously working to undo the incentives that have fueled the solar industry’s growth. A generous federal tax credit is set to shrink in a few years. It has attracted the attention of regulators, who have questioned the way it values the rooftop systems.

And, because of its stock price, it must continue to feed Wall Street’s appetite.

“The market expects them to grow really rapidly for a while — there’s no other way that that price makes sense,” said Shayle Kann of GTM Research.

But there have been signs of growing pains. In interviews, former employees describe a high-pressure environment that went into hyper-drive when the company went public in December 2012. Complaints to the Better Business Bureau of misleading marketing and flawed installations, along with negative reviews on social media forums like Yelp, appear to be rising.

SolarCity says its employees as well as most of its customers are happy, and that its ratings have remained high. But the bad reviews have attracted the attention of Peter Rive, one of SolarCity’s co-founders and its chief operations officer. He regularly responds to the criticisms on Yelp.

“Any negative review that we get, be it through Yelp or through our own customer satisfaction survey, I take very seriously,” Mr. Rive, 39, said, adding that nothing he had seen indicated that service was deteriorating, despite the rapid growth. He delves into complaints, he said, “just because it bugs me — every single time somebody has a negative review I want to understand” the root cause of the problem.

SolarCity is not the first venture for the Rive brothers nor for Mr. Musk, who made a fortune as a co-founder of PayPal. The Rives were working at a computer services company that Lyndon Rive had started with another brother, but he was getting antsy.

“I wanted something that would be long-lasting,” Mr. Rive, 36, said. “And something that could solve some of the environmental challenges we’re facing.”