Solar Thermal

CNet.com:

Solar thermal water heaters, which use solar energy rather than gas or electricity as a power source, could grow in popularity over the next few years, according to analysts and panel installation companies....

Partly driving the interest--besides global warming and rising energy costs--is the fact that the systems work quite well. It is far easier to extract heat from the sun than electricity, according to Gary Gerber, CEO of Sun Light and Power, which installs solar systems. Solar thermal heaters ultimately use about half of the heat that hits them; that makes them two to three times more efficient than the solar panels that turn sunlight into electricity.