It's been a good year for Elon Musk.
Last week, Tesla Motors ( -- the electric-car company he heads and co-founded -- recorded its )first-ever quarterly profit, exceeding sales targets. Its Model S was deemed the best car ever reviewed by influential Consumer Reports and shares have soared nearly 60% since those two pieces of news. SpaceX, his space exploration company, became the first commercial venture to successfully attach a vehicle to the International Space Station last May, and it repeated the feat in October.
Then there's SolarCity (, the renewable energy firm chaired by Musk and founded by his cousins, brothers Lyndon and Peter Rive. The company )debuted on the Nasdaq in December at $8 a share and has since seen its stock price quadruple, closing at $35.88 on Monday.
SolarCity offers solar-power systems for homes and businesses, designing and installing custom-built arrangements. The firm reported Monday that its customer base had grown 106% versus a year ago to over 57,400, while first-quarter revenue rose 21% to $30 million, ahead of the $29 million predicted by analysts surveyed by Thomson Reuters.
But the seven-year-old company posted a loss of roughly $31 million for the quarter, or 41 cents a share. It also offered weak second-quarter guidance, sending shares down 11% in premarket trading Tuesday.
Pavel Molchanov, an analyst Raymond James, said SolarCity's stock had clearly benefited from the company's association with Musk. SolarCity shares surged 35% between when Tesla reported its earnings last week and Monday's close.
Molchanov said SolarCity's share price was "not rational" based on its fundamentals, but Raymond James still maintains a "neutral" rating on it.
"It's a story stock, and with story stocks, sometimes valuation doesn't matter," Molchanov said.
Solar-energy companies have struggled in recent years, as U.S. firms face competition from cheaper solar panels manufactured in China. Solyndra, which received a $535 million loan from the U.S. government, has been the highest-profile casualty. The company declared bankruptcy in September 2011 and laid off all its employees.