Free fuel and clean operation are just two reasons people add solar water heaters to their homes. A homeowner switching to solar from an electric water heater could save up to $500 in the first year of operation, with savings increasing as electricity rates rise. Solar heaters cost a lot more but can usually be paid off in three to seven years. A passive system can set you back $1,000 to $3,000, and an active system costs between $2,000 and $4,000.
Most solar systems don't work entirely on their own; they are either integrated into storage water heaters or have one as a backup.
Active solar water heating
Active solar water heating can take place in two ways:
In either method, a solar collector is mounted on the home, facing south. Sunlight is absorbed and converted to heat, which is prevented from escape thanks to glazing. Two popular types of solar collectors are:
Heat transfer fluid flows through the collector and transfers heat to water in a storage tank. A pump powering fluid movement is controlled by electricity, either in the form of an electrical wall socket or via a small photovoltaic module beside the solar collector.
Passive solar water heating
Less expensive but not as efficient as active systems, passive systems have the potential to last longer and can be somewhat more reliable. There are two main passive solar water heating systems:
What to look for
Talk to an experienced solar-water-heater installer to find out whether your home provides the right conditions to make it worthwhile. Find out if others in your area have solar systems and ask how they have found the experience.