When it comes to producing electricity for homes and businesses, for example, the most readily deployable alternative to fossil fuel is wind.

For small investors who think climbing oil prices are bound to spark greater interest in other sources of power eventually, some of the most interesting plays could be among traditional companies that are exploring alternative energies - General Electric Co., FPL Group Inc. and BP PLC.

The problem with most companies focused purely on non-petroleum power is they tend to be relatively young, have weak balance sheets and frequently focus on technologies that aren't yet commercially viable. Some of the most attractive investments are overseas, and not readily available to U.S. investors.

"Unfortunately and tragically there are simply not a lot of alternative energy sources being developed," said Stephen Leeb, president of Leeb Capital Management and co-author of The Oil Factor, which suggests crude prices will likely strike $100 a barrel by the end of the decade, if not sooner.

"It's sad, but that's the reason oil is at nearly $50 per barrel," Leeb said. "If there were a whole universe of alternative energy companies making lots of money, you probably wouldn't have an energy crisis today."

With so much money yet to be made in oil, there hasn't been a great deal of investor interest in renewable sources of power, analysts say.

"It's been an interesting disconnect," said Matthew Patsky, portfolio manager of the Winslow Green Growth fund. "The renewable energy stocks in general went down when oil was falling and went down when oil was rising. You'd think they'd trade with oil ... but it's been a tough market for renewable energy stocks in general, and particularly for the fuel cell companies." There are high hopes that emission-free hydrogen fuel-cells will replace gas-guzzling cars and start producing power in homes, but this technology is still in the early development stages. Companies like FuelCell Energy Inc., Plug Power Inc. and Ballard Power Systems Inc., a Canadian concern partly owned by auto manufacturers Ford Motor Corp. and DaimlerChrysler AG, remain unprofitable.