Imagine filling your bathtub full of steamy water, knowing you did it without creating pollution or wasting money. Solar water heaters can supply hot water to your tap for less money while helping you reduce your contribution to global warming by decreasing the amount of nonrenewable energy you use.

Solar water-heating systems use clean, free energy from the sun to heat water for daily use or for space heating. About 15 to 20 percent of a household’s energy outlay goes to heating water for bathing and washing clothes and dishes. A solar water-heating system is the most cost-effective renewable-energy investment a homeowner can make.

The upfront cost for a system and installation is steep, typically ranging from $4,000 for a small system to $20,000 or more. However, you’ll enjoy an instant increase in home equity, and you’ll immediately reduce utility bills while also protecting yourself from energy rate increases. Because the energy is free, there are no monthly bills. Once the system has paid for itself in savings, the hot water your solar system provides costs you nothing. On average, a solar hot water system pays for itself in five to 15 years, depending on the system type and financial incentives in your area.

Many people finance solar heating systems, making monthly payments. The energy savings are usually large enough to offset the loan payment, so your monthly expenses don’t increase.

How do solar water heaters work?

Solar collectors need direct sun to function. They’re mounted on a rack in a sunny spot, either on your roof or in the yard. Insulated piping connects collectors to a storage tank near your existing water heater. A pump circulates antifreeze or water through the collectors whenever the sun is shining. This hot solar fluid then goes through a heat exchanger to preheat your water and store it in a tank for later use.

A solar professional can assess your home to determine the best location for the system, give you a cost estimate and determine what services a solar system could provide at your house. Solar collectors should be mounted within 30 degrees of true south and tilted at an angle equal to your latitude.

Solar water-heating systems aren’t designed to provide 100 percent of a home’s water. A typical system provides 50 to 75 percent of the annual load. The amount of energy your solar system can provide depends on your climate and the time of year. In warmer climates or during the summer, you can expect your solar water heater to provide nearly all of your needs; during overcast periods, output can decrease to 50 percent. You’ll need a backup water heater for use during cloudy weather.