Sun power: solar thermal hot water systems save energy and money.

Not only does Bob Aresty of the Solar Energy Industries Association talk the energy-saving talk, he walks the walk. Aresty's beach home has a passive solar thermal hot water heating system because he says such systems are cheaper to operate and more efficient than traditional electric or gas

Other solar thermal proponents are seeing the light, so to speak, including California Governor Arnold Schwarzenegger, who recently joined with energy experts and the governors of New York, Texas, and Florida to encourage Congress to pass energy tax credits for such products. According to these forward thinkers, solar thermal systems, which use sunlight to heat water in rooftop collectors that is then stored in tanks for use throughout the home, are the wave of the future because they save both energy and money.

ON THE REBOUND

Available for decades, solar thermal hot water systems are beginning to bounce back after taking a nosedive in the '80s.

"The problems began in the end of 1985 when the Reagan administration and Congress eliminated the 40 percent tax credit available to most Americans that encouraged the installation of solar water heating systems," recounts Bill Guiney of Solargenix Energy, a manufacturer of solar energy products.

These days, the federal government is working to turn back the clock with programs that support solar thermal power. For example, the Million Solar Roof program operated by the DOE began promoting in 1997 the installation of solar energy systems--including photovoltaic and solar thermal--in commercial, municipal, and residential buildings.

As of December 2003, there were more than 300,000 solar energy systems of all types in place, says Katy Ansardi, outreach coordinator for the North Carolina Solar Center, which is part of North Carolina State University's College of Engineering. Many solar thermal systems are in public, municipal, or government buildings because these spaces guzzle large quantities of water.

But awareness of the Million Solar Roof program and other renewable energy efforts by consumers and home builders is swelling. The North Carolina center manages the Database of State Incentives for Renewable Energy Web site that the DOE funds. State and federal rebates (including solar thermal incentives) are piquing both builders' and homeowners' interest, translating into 20,000 hits a month for the Web site, Ansardi says.

HOW IT WORKS

Designed to provide up to 80 percent of a home's hot water supply, solar thermal systems often get lumped in with photovoltaic systems, but they're not the same. Photovoltaics, which trap sunlight to produce electricity and don't heat water, are the "sexy" part of solar, says Tom Bohner, president of Sun Systems, maker of solar thermal products. They're perceived as more useful because they generate electricity; solar thermal systems just heat water.

But solar hot water systems reduce homeowner expenses. "A solar water heater should save $200 to $300 per year for a family of four," says Guiney of Solargenix Energy. The savings is based on 70-gallons-per-day usage.

Although the systems are expensive--$1,500 to $4,500, installed--they easily can be rolled into a mortgage. What's more, state incentives, particularly in the Sun Belt, make it possible to recoup the initial system costs.

A few builders are smitten by the benefits of solar hot water, in 2001, California-based Shea Homes created a neighborhood of more than 200 high-performance homes that offered solar water heating as a standard feature and photovoltaic panels as an option. According to Bohner, who worked with the firm and taught crew members how to install thermal hot water systems in the Scripps Highlands community in the San Diego area, the dwellings were a huge success because of their overall energy efficiency.

A TOUGH SELL

Despite the advantages, solar hot water is a tough sell. Many homeowners and builders are put off by the higher upfront costs, which can be six to seven times higher than traditional systems. In addition, a solar thermal system requires a backup--another expense.

Plus, "[government] funding is always up in the air," Ansardi comments.

"Conventional water systems are not efficient, but they're cheapest and easiest," admits Kyle Andrews of the DOE's Energy Star communications department.

Besides higher costs, many builders and consumers have a "if it's not broke, don't fix it" mentality, Bohner says. Furthermore, most don't understand that solar thermal systems reduce utility bills because they don't use electricity to heat water, he adds.

For Palo Alto, Calif.-based Clarum Homes, solar thermal hot water systems are a possibility down the road. Although Clarum incorporates photovoltaic panels, high-performance furnaces and insulation, and other energy-saving products in its ultra-efficient, nearly zero-energy houses, it hasn't added solar thermal to the mix because company officials don't think it's a proven technology yet.

But, predicts Linda Schieffelin, Clarum's senior purchasing agent: "Everything that's connected with solar is evolving and in the coming years [all types of solar power] will be used more."

RELATED ARTICLE: Solar thermal tips.

All solar hot water systems consist of roof-mounted water collectors and storage tanks, but they vary in other ways. The following information from the DOE's Energy Efficiency and Renewable Energy Web site (www.eere.energy.gov) explains the differences and provides tips:

* Active systems use electric pumps and valves to circulate water (open loop or direct configurations) or heat-transfer fluids such as diluted antifreeze (closed-loop configuration) to transfer heat to household water.

* Passive systems move water or heat-transfer fluid through the system without pumps and are less expensive than active systems.

* Conventional backup systems are necessary for both active and passive systems in nearly all applications.

* Storage tanks usually come in 50-, 60-, 80-, and 120-gallon capacities. A small 50- to 60-gallon system is adequate for a household of one to three people; a medium 80-gallon system for three to four people; and a large 120-gallon system for four to six people.

* In Sun Belt states, allow about 20 square feet of collector area for each of the first two family members and 8 square feet for each additional member; add 12 to 14 additional square feet per person in the northern United States.--S.H.