A solar hot water system is made up of two main parts: solar collector panels and a storage tank. For a home with four people, you usually need a solar collector area of about four square metres (two panels) and a tank size of about 300–360 litres. In order to accommodate times when there is less sunlight or you need more hot water than normal, you will need a large tank.
Most thermosiphon systems have both the panels that collect heat and the tank that stores it on the roof. The thermosiphon effect—where water gets lighter and rises into the tank when it heats up—causes the liquid in the panels to move around in the tank.
Collector panels for pumped or split systems are placed atop the building, while the tank is situated on the ground below (or elsewhere in the building). The solar panels feed the tank with heated water using a pump.
If the panels aren’t put in the best spot, which is usually a part of the roof that faces north and isn’t in the shade, they might not work as well as they could. In this case, you will require a larger collector area.
Flat panels or evacuated tubes can be utilised as collectors. Evacuated tubes are generally more efficient and, as a result, require less panel area. However, the cost of utilising evacuated tubes is higher.
On cloudier days or on days with less direct sunlight, the water in the storage tank is typically heated by an electric or gas booster element.
In regions that are prone to frost, the water in the panels can freeze, causing damage to the panels. Because of this, you need frost-resistant panels, which heat the tank with a special heat-exchange fluid rather than heating the water directly.
Solar hot water systems can be relatively more expensive and time-consuming to install in comparison to conventional gas and electric hot water systems. However, a well-chosen system will pay for itself in the long run due to very low operating costs, so it is worth the investment.