Optimism is hard to find among some Wall Street analysts as two American solar companies get ready to discuss their earnings.

Some analysts are taking a dim view of SunPower Corp. (NSDQ: SPWRA/SPWRB), which is scheduled to release its quarterly and 2008 financial figures after the market closes on Thursday.

Jeff Osborne at Thomas Weisel Partners believes the solar panel maker, based in San Jose, Calif., will face tougher times ahead than what SunPower has anticipated. The company already warned investors back in November that revenues for the fourth quarter of 2008 and this year would drop, but attributed the changes to foreign currency fluctuation (see Stocks Stumble After SunPower Lowers Forecast).

The company expects to generate $388 million to $418 million in revenue for the fourth quarter, with earnings of between 24 cents and 31 cents per share and a gross margin of 24 to 25 percent. For 2009, SunPower anticipates bringing in $2 billion to $2.1 billion in revenue, with earnings of $1.68 per share.

In a research note this week, Osborne said the 2009 revenue is like to be even lower. He's reducing the revenue estimate from $1.97 billion to $1.38 billion.

The credit crunch will continue to squeeze SunPower's business, which includes not only making panels but also installing them, Osborne wrote in this week's research note. Uncertainties over the once-booming market in Spain, whose government has significantly downsized its solar incentive program for 2009, does not bode well for the company.

"Despite SunPower being a best of breed solar company which we believe will outperform in a credit recovery, we do not think they are immune from the market turmoil," Osborne wrote.

Mark Bachman at Pacific Crest Securities, meanwhile, doesn't even consider SunPower to be one of the best solar companies around. In a research note this week comparing SunPower to First Solar, another large American panel maker, Bachman said a solar power plant built with SunPower's equipment doesn't necessary perform as well as the company likes to claim. 

Bachman made a similar comparison in a previous research note and saw First Solar as a stronger competitor in the marketplace (see First Solar Reaches Grid-Parity Milestone, Says Report).

Bachman lowered his estimate of SunPower's 2009 revenue to $1.8 billion from $2.1 billion.

First Solar (NSDAQ: FSLR), long loved by investors and analysts, isn't immune to Wall Street's bearish outlook. The company, based in Tempe, Ariz., has built a reputation for being able to produce solar panels cheaper than anyone else in the industry.

Osborne at Thomas Weisel Partners has cut his estimates of First Solar's 2009 revenue and production, citing difficulties in gauging market demand this year. He expects the company to produce 837 megawatts worth of panels instead of 975 megawatts in 2009, and the annual revenue to reach $1.72 billion instead of $1.99 billion.

In discussing its third-quarter earnings last October, First Solar executives said they expected to generate $2 billion to $2.1 billion in revenue this year (see First Solar Profits Up 54%, Credit Crunch Could Impact Biz).

In a research note this week, Gordon Johnson at Hapoalim Securities said he believed First Solar's own forecast "could prove out of line with reality." Johnson expects the company's 2009 revenue to be around $1.7 billion at the low end.  

In a recent interview, Johnson said First Solar will face tougher competition this year because the price for polysilicon is dropping quickly. Polysilicon is the main ingredient used to make most of the solar panels on the market today. SunPower and Suntech Power Holdings, for example, use polysilicon in their panels.

Polysilicon used to be pricy. With more polysilicon factories coming online, however, the prices are falling quickly (see Polysilicon Prices Head For a Steep Fall). First Solar uses cadmium tellurium instead.

"First Solar has had a cost advantage because it doesn't have to buy polysilicon. But it's going to crash and crash again even harder than Suntech," Johnson said.

First Solar plans to release its earnings on Feb. 24.