First, the system for a solar water heater has to be selected. We have to choose between an active and a passive solar hot water system either with a direct or indirect water distribution.
Then we have to select the type of collector for our solar water heater. Most common are flat plate or evacuated tube collectors. In regard to the position of the collectors we have to consider that it is optimal when collectors are facing south with a tilt of 35 degrees.
The thermal storage cylinder for a solar water heater has to be sized and should be able to provide 40-60 liters per day for the household. We have to decide between vented, mains pressure and thermal store cylinders. For pre-heating water storage the most common cylinders are single cylinders with twin coils or a distinct pre-heat tank which is placed before the conventional cylinder of a solar water heater.
An important detail is the right sizing of the pipe line. When pipes are too wide, up to 50% of the heat can be lost. The pipes in a correctly installed solar water heater should route and control the flow of the heat transfer fluid with minimum power requirements.
An active solar water heater requires a circulation pump that circulates the water or heat transfer fluid through the pipes. An efficient pump should provide the required flow rate with the minimum amount of electricity.
A solar water heater may provide enough hot water during warm summer months, but usually has to be supported by other heating systems during winter. There are a number of options like electrical resistance heating or a gas powered boiler.
Before installing a solar water heater, the energy efficiency of a system should be calculated. This can only be done accurately with the help of a professional installer.