Even as oil trades near record levels, shares of renewable-energy companies are far from a sure bet.

Stocks of companies that generate electricity from solar or wind power -- or make the equipment to do so -- soared during the last three years. But the global credit crunch, higher prices for raw materials like polysilicon used in solar panels, and cuts in government subsidies to consumers, such as in Germany last month, have made investors much warier. High oil prices, analysts say, can't compensate for all that.

"Some months ago, it was still true that a rising tide lifts all the boats," said Thomas Germann, an analyst at Zuercher Kantonalbank. "But investors are now scrutinizing what's going on at the company level, because cost efficiency has become more important."

A proxy for the changing sentiment is Conergy, a German solar and wind company that was long a sector darling. But it posted a large net loss last year as it struggled with soaring costs. Investors question whether it can return to profitability as promised next year. The stock has plunged 71% since problems were disclosed Oct. 26.

Such news has sobered the anything-goes mood reminiscent of the Internet boom. That's reflected in the lackluster showing of two recent large initial public offerings.

Last year's IPO for €4.1 billion ($6.35 billion) by profitable wind-energy producer Iberdrola Renovables SA, a unit of Spanish Iberdrola SA, is down 15% from its €5.3 offering price. Some analysts say the problem is that the stock was too pricey to begin with, and even now trades around 40 times expected earnings. Some say the company is too similar to traditional utilities that trade on much lower multiples.

Investors skeptical about the ability to contain costs gave a cold shoulder to Energias de Portugal's wind-energy division, EDP Renovaveis, which raised €1.6 billion earlier this month. Shares closed Tuesday at €7.88, down from the €8 IPO price. EDP Renovaveis earned €4 million on revenue of €339 million.

"The easy money has been made," said Jean Ryan, who oversees three funds with about €2 billion in assets at KBC Asset Management International Ltd., a unit of Belgium-based KBC Group NV.

The next test for the sector could be initial public offerings for SMA Solar Technology AG, a solar-energy control-system producer, and Sinosol AG, a German-Chinese developer of turnkey solar parks, which want to list in Frankfurt. SMA Solar posted sales of €330 million in 2007 and a net profit of about €40 million. The smaller Sinosol earned €2.2 million in pretax profit for the six months through March 31 on sales of €35.6 million.

"SMA Solar is profitable and big enough to make it," said Pius Gasser, managing director of Swiss financing company Phoenix Capital Ltd. and one who intends to seek shares in the company. "At a later stage, smaller companies such as Sinosol could be interesting, as well as they could become takeover targets."

Some say the recent selloff has opened up opportunities. Fund managers say valuations for the sector generally now seem reasonable, as shares trade between 20 and 30 times expected 2008 earnings, rather than around 80, as was the case last year. Vestas, the world's largest and most profitable wind producer with €4.8 billion in sales in 2007, has a price-earnings ratio of 32.7. The stock has gained 25% this year.

Another support could be takeover hopes. Robert Bosch GmbH earlier this month said it would spend €1.08 billion to buy Ersol Solar Energy AG, which makes solar cells. The price represents a 63% premium to the closing stock price just before the bid was announced.

Landing business helps, too. Gamesa has jumped 11% in the three days since it announced a €6.3 billion deal to provide wind turbines, construction and services to Iberdrola Renovables. It is the largest wind-turbines deal ever.

Ms. Ryan, the KBC investment specialist, prefers fast-growing companies that can capitalize on long-term trends of curbing carbon-dioxide emissions, improving waste management or limiting energy consumption. One of her picks is profitable German solar-cell producer Q-Cells AG, which has sales of about €900 million. The stock has plunged 25% so far this year.

But she also owns stocks of established firms such as Swiss engineering titan ABB Ltd., which profits from demand for products that enhance energy efficiency.

Thiemo Lang, fund manager at Sustainable Asset Management in Zurich, with €335 million under management, likes companies that supply other companies with components for their products. He says they have more pricing power.

Among the stocks he holds are Yingli Green Energy, which makes photovoltaic products and is listed in the U.S., SunPower Corp., the largest North American solar company by sales and traded on the Nasdaq Stock Market, and Q-Cells. Yingli has plunged 49% this year, and SunPower has dropped 36%.

"After the market weakness earlier this year, renewables are in demand again," he said. "But we won't see the price spikes of the past."