That's in contrast to photovoltaic, or PV, technology. Companies like SunPower make solar panels that take the rays of the sun and convert them into electricity without water or a turbine. Though much cheaper to get up and running, PV solar produces power at a cost of more than 30 cents per kilowatt-hour, compared with about 20 to 22 cents per kilowatt for solar thermal plants, Tisdale says.

PV solar, though, has exploded in places like California and Germany thanks to heavy government incentives. Homeowners and companies such as Wal-Mart WMT and Google GOOG are putting PV panels on their roofs, using the energy created in-house and even putting some excess power back onto the grid.

In 2006, 1,700 megawatts of PV technology was installed worldwide, 20% more than the previous year, and the pace picked up this year, Tisdale says. One megawatt is enough for 750 to 1,000 homes.

Zero solar thermal watts went up last year, but 96 megawatts are expected to go live this year, Tisdale said, and there are plans to add some 5,000 megawatts of solar thermal capacity worldwide by 2012.

Take Pacific Gas & Electric. Late last month it said it would double its commitments to buy solar thermal electric power. It now plans to add 1,000 megawatts of new supply during the next five years. By comparison, it has less than 200 megawatts of PV projects planned, Wachs says.