In most homes the geyser is the appliance that uses the most electricity. Geysers use electricity all day to keep the water in the tank constant. This requires much electricity, resulting in much coal being fired with air pollution as a result. The less one uses the geyser, the less electricity is used. This is why many people switch their geysers off during the day.
Installing solar geysers is also becoming popular although it is relatively expensive even though Eskom does give rebates for the installation.
The way it works is that the sun shines (radiation) on a panel called the ‘collector’ which has black tubes containing water which heats up. As hot water rises, the water moves into the geyser and settles near the upper surface (convection). Cold water will settle at the bottom. When a tap is used, the hot water from the top of the geyser pours out. Water circulates in the system moving cold water into the panel for heating.
If the geyser is installed below the panel, a pump must be installed to circulate the water. A controller is also used to measure water temperature and pressure to make sure that the system works smoothly.