NEW YORK (Reuters) - GT Solar International Inc’s initial public offering, expected to be the largest ever by a U.S. solar company, is facing a surprisingly cloudy outlook.

Solar panels are seen on the roof of a building in a file photo. REUTERS/Kimberly White

Despite red-hot industry growth, as the price of competing energy sources soars, investors have not shown a sunny disposition toward solar energy stocks lately.

The stocks of industry leaders Suntech Power Holdings Co Ltd STP.N and Applied Materials Inc AMAT.O, among others, have been cooling from March rally levels since late May. Suntech is down about 18 percent from its high in spring, while Applied Materials is down about 9 percent.

Those declines could cast a pall over GT Solar, a Merrimack, New Hampshire-based maker of the manufacturing equipment used by solar energy companies, whose IPO is scheduled for this week.

“It’ll hurt that solar stocks have been volatile,” said Samuel Snyder, a senior research analyst with Greenwich, Connecticut-based advisory firm Renaissance Capital. “But investors will see unique aspects that make GT Solar attractive.”

One of those advantages is GT Solar’s position as one of only a few makers of the manufacturing equipment used by the solar companies, analysts say.

“It’s a less fragmented arena,” said Pavel Molchanov, an alternative energy analyst with Raymond James & Associates. “The landscape is not quite as competitive.”

GT Solar’s regulatory filings also reveal a compound annual growth rate of 128 percent in the past two years that should comfort investors, with revenue of $244 million for the year that ended in March.

That growth rate explains why GT Solar would trade at 66 times 2007 earnings if the IPO priced at the midpoint of its forecast range, a high multiple compared with those of other solar stocks, said Scott Sweet, an analyst with IPO Boutique.

GT Solar’s IPO is forecast to price in a range of $15.50 to $17.50, with a midpoint of $16.50 a share.

“Their growth is astronomical and they have a backlog, so it will support a higher price earnings ratio,” Sweet said. In its filing, the company said it has an order backlog of $1.3 billion.

Other solar companies have widely varying multiples based on 2007 earnings, from a price/earnings ratio of nearly 36 for Suntech and 15 for Applied Technologies. First Solar Inc FSLR.O, one of the few solar stocks doing well lately, is trading at a multiple of nearly 200, while SunPower Corp's SPWR.O multiple is 60 and LDK Solar Co Ltd's LDK.N is 26.

SKITTISH INVESTORS

Investors are skittish about cutbacks to subsidies in Spain, a major market, and the uncertainty during an election year around the renewal of a U.S. federal tax credit set to expire in December and that has spurred industry growth.

The tight market for silicon, a key component in the process of turning sunlight into power, might hurt solar energy’s economics, as could a sustained fall in oil prices.

While oil does not have a direct correlation to demand for solar power, since most electricity in the United States is generated from coal or natural gas, higher crude oil prices generally help boost investor interest in renewable energy.

Last year saw a spate of solar IPOs in the United States, including Chinese manufacturers LDK Solar and Yingli Green Energy Holding Co Ltd YGE.N. In 2008, there has been only one solar IPO so far, Real Goods Solar Inc's RSOL.O modest $55 million debut in May.

Should GT Solar raise $500 million as planned when it goes public, the offering will be the largest-ever U.S. solar IPO and the sixth-largest U.S. IPO of the year overall, according to data from Dealogic. The company plans to list on the Nasdaq under the ticker "SOLR" SOLR.O.

THE REAL DEAL

Even if solar subsidies were scaled back, the market has reached a maturity and viability that should reassure investors, analysts say.

“There is a disconnect between the fundamentals of the industry and how stocks are trading,” Molchanov said.

“Solar adoption rates are still barely scratching the surface,” he said, pointing to solar energy’s 0.1 percent share of the U.S. electric power market, and the 3 percent share in Germany, by far the world’s largest market.

According to data from research firm Global Markets Direct, solar energy was an $18 billion global industry in 2007, growing at a pace of about 35 percent per year in the last three years. In the United States, the $1.4 billion market is growing even more quickly, at a clip of 60 percent per year.

Ultimately, of course, how GT Solar performs at its debut may hinge on how the capricious markets are feeling that day, said Sal Morreale, who tracks IPOs for financial services firm Cantor Fitzgerald.

“In an environment like this, an IPO like GT Solar is day to day,” he said.