How does a solar geyser work?
Solar water heaters use the radiation from the sun to generate heat. The size of the solar panel will determine how much energy can be collected from the sun. For example if you have a 4sqm or bigger flat plat solar panel connected to a 300L geyser, this should give you 300L of 60°C water at the end of a warm sunny day. The same applies with an evacuated tube system, whereby the bigger your geyser, the greater the number of tubes you need to heat your water.
During cooler days with less sunshine you may still need a geyser element to supplement your hot water heating usage. Today, solar systems are installed with very smart timing systems which allow you to specify time zones for when you want to have hot water, for example at night between 6pm and 9pm when you take your bath, and again in the morning between 5am and 8am. Your system will work to ensure that you always have hot water during these times to the specific temperature. If the temp drops to below your specified requirement and there’s no sunshine at that time to reheat it, your system will kick back to the geyser element to supplement your hot water. It will only do this if necessary, so the savings are significant. In fact, a properly-sized solar geyser can cut your monthly electricity bill by anywhere between 30-40% of your total cost.
When going solar, as a rule of thumb, each person in the household uses around 70 litres of hot water a day. Check with your supplier about the size and the power output of the system. An under-sized or low efficiency system will result in insufficient hot water and a poor realisation on electricity savings, defeating the whole purpose of why you bought the system.