Solar hot water heating systems are relatively simple to install, easy to maintain and the most cost effective way to introduce your home to solar energy. They can save considerable energy and cost when they replace an electric hot water heater. And they can be successfully used even if you live in a climate where freezing temperatures are common during the winter.
If you live in a climate that does not have freezing temperatures, and your household consists of fewer than five people, you can install a batch heater. This is the least expensive solar water heating option, and it is relatively easy to build if you have the inclination to do-it-yourself. It is simply a water storage tank that also serves as the solar collector.
The tank is enclosed in a glass-covered box that is positioned to allow maximum exposure to the sun. The water in the tank heats up and hot water is available for use. However, it is not the most efficient system, since it takes longer to heat an entire tank of water than to heat a flat panel solar collector. And as the tank cools at night, there is less hot water available for use.
There are two better systems that can be used even in freezing climates. The direct pump system circulates water between a solar collector and a storage tank. With this design, water in the solar collector can heat up faster, and the tank can be insulated for better temperature holding capacity. The pump can be designed to run on electricity from a photo-voltaic cell if you want to keep your system completely solar powered.
A thermosiphon system also uses a separate solar collector, along with the pull of gravity. And it allows for the use of an insulated storage tank for more consistent hot water delivery. When using either of these systems in cold climates where freezing is an issue, both the piping and the storage tank should be located indoors and properly insulated to provide hot water even on the coldest days.