Also known as solar domestic hot water systems, solar water heaters bring important savings to a home by generating hot water for practically free.
Solar water heaters usually include two major components: solar collectors and storage tanks. There are three types of solar collectors: flat-plate collectors, integral collector-storage systems and evacuated-tube solar collectors. As for the storage tanks, in one-tank systems the back-up heater is merged with the solar storage in a single tank, while in two-tank systems the water is preheated by the solar water heater before entering the conventional water heater.
Solar water heater systems can be either active, meaning the water circulates through pumps, or passive. There are two possibilities for active solar water heaters: direct or indirect circulation systems. For climates where freezing is not often, the direct circulation system is the right option because the water is circulated by pumps through the collectors then into the home. On the other hand, for climates where it generally freezes, the indirect circulation systems are the recommended ones because it implies the use of a heat-transfer fluid through the collectors as well as of a heat exchanger.
Passive solar water heaters are considered to be less effective as the active ones, but they are cheaper and can last longer. Passive systems feature two types: integral collector-storage passive systems and thermosyphon systems. The difference between them is that the first one is built for areas where it freezes and the second one for a cooler climate.
Most solar water heaters need a backup system for days with clouds or times when the demand of hot water is higher. These backup systems usually come with the solar water heating systems.
You should take into consideration several aspects before purchasing solar water heaters. For example, you should think about the economics of this kind of system, evaluate the solar resource of your house, establish the right size, estimate the costs and check local regulations and codes regarding this matter.
In addition, do not forget that proper installation is a must, so it is better to hire a thermal systems contractor to install your solar water heater, as there are many factors that influence this process.