Short-selling specialist Jim Chanos is stepping up his attack on two companies led by billionaire entrepreneur Elon Musk.
"Of all of his companies, I think the one that's most problematic is SolarCity because they're burning $300 million to $500 million a quarter putting up solar panels that may not be worth anything in 20 years," Chanos said Wednesday during a wide-ranging interview on CNBC's "Squawk Box."
Chanos, whose Kynikos Associates firm has $3.3 billion in assets under management, originally told CNBC about the SolarCity short position around midday on Fri., Aug. 21, and the stock plunged 12 percent.
Hours after Chanos announced his short and questioned the cost benefit to customers who "basically lease the panels" in hopes of paying less for energy, SolarCity CEO Lyndon Rive told CNBC the Kynikos founder doesn't have his facts straight. "We sell them energy at a lower rate than they can buy from the utility."
On Mon., Aug. 24, SolarCity Chairman Musk bought nearly 124,000 additional shares at just over $40.48 each.
Since the Chanos short was revealed, SolarCity shares had recovered 8.6 percent as of Tuesday's close. SolarCity was about 3 percent lower in early trading Wednesday.
Comparing SolarCity to electric automaker Tesla—another Musk company and Kynikos short—Chanos said: "Tesla, people will fund it. It will sell cars. I just don't think it's worth" the valuation or the price of the stock, which closed Tuesday at about $248 a share.
"Tesla is being valued, according to 'our friends' at various different brokerage houses, on 2025 earnings and cash flow that may or may not happen," Chanos said. "It is sort of silly."
To make his case, he cited a published report from earlier this year that made the rounds again this summer, in which BMW was said to be aiming to convert the bulk of its product lineup to electric over the next 10 years.
Chanos said he can't see why stocks like Tesla, which he calls "momentum" or "concept" names, should be hotter than "real companies, with real products" like BMW, which are also going to innovate and compete on technology.