Because it saves natural resources, reduces carbon emissions, and offers a money-saving opportunity for homeowners, solar water heating was named one of the top 10 technologies for 2007 by the Department of Housing and Urban Development's Partnership for Advancing Technology in Housing (PATH) program.

With more homeowners willing to consider the technology as a way to green their homes and reduce their energy consumption, solar water heating is experiencing a comeback after a nearly 20-year hiatus. “What we're seeing now is a renaissance of interest [because of] new federal tax credits and the rising price of energy,” says Noah Kaye, director of public affairs for the Solar Energy Industries Association (SEIA).

Photovoltaics, or solar electricity, gets most of the attention when builders consider renewable energy systems, but solar water heating offers a more cost-effective way to incorporate renewables into a home. “Solar water heating can be as little as one-tenth the cost of photovoltaics. It's a much more efficient use of the sun's energy at a lower cost,” says Jeff Mahoney, North American representative for Rheem USA's Solahart division. Plus, the payback on a solar water heating system can range from five to 10 years, faster than a photovoltaic system's estimated payback period.

Rheem USA The passive, closed-circuit Solahart Free Heat series solar water heating system uses a multi-flow collector panel that exposes more water to the sun's radiation than standard collector designs, heating water faster. Its black-chrome selective surface provides high-efficiency energy absorption. Integrated storage tanks range in capacities from 48 gallons to 116 gallons. 334.260.1586. www.solahart.com.

Rheem USA The passive, closed-circuit Solahart Free Heat series solar water heating system uses a multi-flow collector panel that exposes more water to the sun's radiation than standard collector designs, heating water faster. Its black-chrome selective surface provides high-efficiency energy absorption. Integrated storage tanks range in capacities from 48 gallons to 116 gallons. 334.260.1586. www.solahart.com.

Though the concept is attractive, it works best as a supplement to standard and tankless water heaters, according to most manufacturers of the technology. Nearly anywhere in the U.S., a solar water system can supply 60 percent to 70 percent of a home's domestic hot water, according to Tim Bowler, solar sales and technical services manager for Stiebel-Eltron. The U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy states that a solar water heating system reduces the need for conventional methods by two-thirds.

Different types of systems are available to meet the conditions of most regions. Passive systems are designed for warm climates and can store heated water in an integrated tank or in the collector plate. Because active systems can use an antifreeze fluid as well as water to collect heat, they are ideal for colder climates. Pumps move the heated water or fluid from the collector to the storage tank in an active system.

Collectors can be installed nearly anywhere the sun will shine for six to eight hours each day, but the best spot is nearly always on the roof. Custom builders can circumvent the aesthetic impact of solar collectors by designing roofs to conceal or camouflage them and orient homes for maximum sun exposure. However, some manufacturers have developed less obtrusive collectors, such as FAFCO's Hot2o system. Its collector panel is made of black polymer tubes with a much thinner profile than flat plate or evacuated tube collectors. Dawn Solar's collector tubes install below roofing materials, protecting them and keeping them out of sight.

Stiebel-Eltron The SOL 25 Plus flat plate solar collector can be combined with the company's tankless water heating system for domestic water heating, space heating, and swimming pool heating. The 3-inch-thick panels use a polypropylene glycol solution for heat transfer. 800.582.8423. www.stiebel-eltron-usa.com.

Stiebel-Eltron The SOL 25 Plus flat plate solar collector can be combined with the company's tankless water heating system for domestic water heating, space heating, and swimming pool heating. The 3-inch-thick panels use a polypropylene glycol solution for heat transfer. 800.582.8423. www.stiebel-eltron-usa.com.

Web sites:

Dawn Solar Systems: www.dawnsolar.com

FAFCO: www.fafco.com or www.hot2o.com

Rheem USA: www.solahart.com

Stiebel-Eltron: www.stiebel-eltron-usa.com

DOE's Office of Energy Efficiency and Renewable Energy: www.eere.energy.gov

Partnership for Advancing Technology in Housing: www.pathnet.org

Solar Energy Industries Association: www.seia.org

Solar Rating and Certification Corporation: www.solar-rating.org