Using solar energy in your home is about as “green” as living can get.

Working on a project to build a simple solar heater is a great family project and can be an excellent learning tool for your children. It is also good for the environment. Reducing overall electricity demand for water heating, especially during hot summer afternoons, can help reduce the need for additional power plants and moderate rate increases over time.

Other than solar swimming pools or spas, solar domestic water heating makes the most economic sense of all solar systems. This is because hot water is needed year-round and water has a very high thermal mass capacity for storing the captured solar heat. Heated water can be moved efficiently through insulated pipes without pumps. The normal house water pressure moves it through the solar system and into your house.

In contrast, whole-house solar space heating systems, unless you make a simple do-it-yourself window heater for one room, often are not cost effective for most of the country. Space heating is typically needed for only about six months each year. Its maximum solar heat output is needed during the winter when the daylight hours are shortest and the sun is most indirect. In some regions, such as Cincinnati where I live, there often is a cloud cover on winter days.

If your budget is limited and your children want to help, building a simple batch-type solar water heater is your best option for this project. This is not as effective as an elaborate active solar system with an array of solar collectors on the roof, but it does not cost thousands of dollars, either. Depending upon the types of scrap materials you can find around the house, you should be able to build a batch system for less than $200 and the savings will pay back its cost in a couple of years.

The energy savings on hot water heating you can expect to realize depends on the specific design and your climate. The sun is more direct in southern climates and less heat is lost to its warmer outdoor air. During the summer, a 50 percent savings on your water heating costs is reasonable, as is a 25-percent savings during fall and spring. In many areas of the country, it is best to bypass the solar heater during winter to avoid freezing and possible damage to the solar heater or plumbing.

A batch solar water heater is used as a preheater for the incoming cold water before it reaches your standard water heater. If the incoming water is warmer, it takes less gas or electricity to heat it to the regular hot water temperature (120 degrees is best). On a hot and sunny summer afternoon, the solar heater can warm water enough so the water heater stays off all day.

The most common design of a batch solar water heater uses a water tank inside of an insulated box with a clear top. Special solar water heating tanks can be purchased, but first contact local plumbers to find one or two old discarded water heaters that do not leak. Strip off the sheet metal skin and insulation to expose the steel tank. It is easy to attach the plumbing because the old tank already has all the plumbing fittings and a pressure relief safety valve.

The water heater tank should be painted flat black. Special solar paints, which are formulated to absorb more solar heat, are also available at a reasonable cost. If you can find one, use an old glass storm door or window for the clear top or buy a sheet of clear acrylic plastic.

For the greatest year-round solar gain, slope the clear top at an angle equal to your latitude angle. Run the hot water outlet pipe from the tank through the back or side of the box and then down near the ground into your house to the water heater. Run another incoming cold water pipe from the water heater to the solar heater. Insulate them very well. Install a crossover pipe and two valves to bypass the solar water heater during winter in cold climates.

The following companies offer solar kits and components:

• AAA Solar Supply, 800-245-0311
• Alternative Energy Store, 877-878-4060
• Build It Solar
• FLS Energy, 877-862-5050
• Solar Components, 603-668-8186