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Tel.: +27 65 840 5164
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SESSA is dedicated to the promotion, use and development of renewable energy and energy efficiency
Domestic Hot Water
The highest energy consumption in the home is from an electric geyser using an electrical resistance element.
The most efficient energy saving technology for replacing electrical heating in a domestic home is a solar water heater (see our section on the basics of solar water heating). Remember, the easiest way to save energy and water is smaller baths or shorter showers.
Low-flow shower heads, where the amount of hot water used reduces to approximately 7-10 litres per minute, instead of 15-20 litres per minute, should be the very first step. They directly reduce water usage and indirectly save energy by reducing the amount of hot water consumed, and therefore enable the hot water to go further. Retrofitting existing shower heads is generally straight forward and does not require a plumber.
Staying with electric water heating through a resistance element is of course an expensive option, if a consumer believes they cannot afford to go solar. Consumers may consider some of the solar rental models, which enable the consumer to be better off immediately over staying with an electric geyser, without the large capital expenditure of buying a solar system.
If the electric resistance geyser is to remain, consumers should for energy efficiency set the thermostat to a maximum of 55 ºC, check that the element is not corroded or heavily coated with lime scale, (this can use up to 30% more power for heating the water), make sure the sacrificial anode is not exhausted, and insulate the geyser with a geyser blanket. To save energy smaller baths or shorter showers will save electricity.
If a home has a mains gas connection, gas boilers are an attractive option to consider being considerably cheaper to run than electric geysers.
Heat pumps are an alternative to solar and electrical resistance elements, but the efficiency is extremely dependant on the temperature of the heat source (usually ambient air for domestic applications in South Africa). Savings in the home depend on the consumer hot water usage profile (i.e. when is hot water used) and the corresponding control strategy (when does the heat pump heat up the water in the geyser) and generic manufacturer savings claims may be misleading.
Other technologies that propose to save electricity, for example induction geysers, should be approached with considerable scepticism. Frequently electrical savings claims are found to be spurious and misleading. Before buying, empirical evidence of savings should be provided.