Solar hot water systems use a thermos-like setup to catch the energy of the sun. (Photo courtesy of Earth Energy Innovations.)

RODALE NEWS, EMMAUS, PA—If you like the idea of getting your power from the sun instead of the electric company, but the cost of lining your rooftop with solar panels dims your enthusiasm, it's time for you to reassess. Dipping solar module prices, coupled with state, federal, and utility rebates, make solar systems more affordable than ever. There's still a significant up-front cost, but you'll see a return of investment in just a few years. (You'll also be putting fewer greenhouse gases and pollutants into the air by drawing less power from coal-fired and other conventional power plants.)

But, you say, you need to keep a close eye on your budget (these days, who doesn't?). Solar power may still be within your grasp. It just might not be in the form of those rooftop photovoltaic panels you've always envisioned. "In most parts of the country, and especially the southern tier—the Sunbelt states—the best bang for the buck is solar water heating," explains Seth Masia, deputy editor of SOLAR TODAY magazine. Solar electric systems can run about $18,000, whereas solar hot-water heating systems cost around $3,000, depending on the typical system (and after rebates).

THE DETAILS: Think of solar hot-water systems as a way to use the sun for some, rather than all, of your electricity needs. The systems allow you to save money on gas or electricity costs associated with heating your home's water, so you can take showers and wash your clothing and dishes knowing that big star in the sky did most of the hard heating work. (If you're building a new construction or putting in new flooring, you may also want to investigate using solar-heated hot water to create radiant floor heating.)

There are different types of solar hot-water systems. The cheapest and simplest type, a single-circuit system, works best in the southern U.S., especially in places like Florida, Arizona, Southern California, and Hawaii, where it never freezes at night. In this system, cold municipal water flows into the home's rooftop collector, which features a coating to heat the water fast using (free) energy from the sun. From there, the hot water moves on to a conventional storage tank.

There's also the thermosiphon system, popular in warm places like Florida and Hawaii. Water in the collector rises through tubes and into the top of a storage tank. When this happens, colder water enters the bottom of the collector, where it can be warmed. For this system, the storage tank is on top of the roof, though, so make sure your roof can handle the load before installing.

Not lucky enough to live in a sunny, mild clime? The evacuated-tube system is more expensive, but it works well even in places that experience cold, snowy winters. Masia describes this system as like a big thermos bottle without an outside cover. Inside its long, tempered-glass tubes are smaller copper tubes surrounded by a vacuum, allowing solar radiation to boil water and create energy even at low winter temperatures.