Solar hot water heating systems provide hot water while using minimal electricity, resulting in reduced energy costs and a more environmentally friendly home. These innovative systems work by collecting heat from the sun in panels mounted on the roof. A special fluid is warmed by the heat in the panels and travels to a collector tank where potable water is stored. The hot fluid passes through a coil in the tank and heats the water before returning to the roof panels.

With this system in place a homeowner has hot water on hand whenever needed without using expensive, fuel-driven energy from the public grid to create it. Solar hot water can offset the electricity is takes to heat all of your household water by up to 90% in an all electric home. Most people don’t realize that an electric water heater is the second biggest user of energy behind your heating and air conditioning in your home.

The size of the solar collectors suitable for your site will depend upon the manufacturer and your hot water usage, but typically they will require between 50 and 100 square feet of mounting area. The most common mounting technique used today is install the collectors flush with the roof on a south facing exposure. Alternatives, such as ground mounting, or rack mounting on gable ends are also sometimes possible.

Two of the more popular systems are the Closed Loop - Glycol System and the Closed Loop - Drain Back System.

Closed Loop - Glycol System

Closed loop systems use a heat-transfer fluid to collect heat and a heat exchanger to transfer the heat to household water. Active closed loop systems use electric pumps, valves, and controllers to circulate the heat-transfer fluid, usually a glycol-water antifreeze mixture, through the collectors. This glycol-water antifreeze mixture makes closed-loop glycol systems effective in areas subject to freezing weather. For this reason, closed loop systems are preferred for year round use in the colder climates.

Closed Loop - Drain-back System

Drain-back systems use water as the heat-transfer fluid within the collector loop. The water is forced through the collectors by a pump and then is drained by gravity to the storage tank and heat exchanger. These systems have no valves to fail and when the pumps are off, the collectors are empty, thereby assuring freeze-protection and auto shut-off if the water in the storage tank becomes too hot.

Paybacks vary widely, but expect a payback of 4 - 8 years on a well-designed and properly installed solar water heater.Shorter paybacks are possible in areas with higher energy costs. After the payback period, savings continue for the life of the system, which ranges from 15 to 40 years, depending on the system and how well it is maintained.