Heating your water

Our homes run on energy. Every time we switch on an appliance, turn on a light, cook our food, or make our water hot we use energy. 25% of all CO2 released into the atmosphere from earth comes from the energy used to run homes. This means actions we take to improve energy use in our homes can really make a difference. Using energy more effciently will also save you money.

Heating your water

Best choice

Traditional electric hot water geysers use up to 60% of your household’s electricity. Heating water over an open fame or on top of a stove can result in fires and burns. It is also the least cost-effective option over time. Though they are initially costly to install, a solar water heater (SWH) is a much more economical and environmentally sound option over time.

Solar water heating (SWH)

South Africa receives strong and regular sun all year round. We have one of the highest insolation (hours of sunshine) rates in the world. Despite this fact, less than 1% of households in South Africa have SWHs. This is largely due to the initial cost of installation, but also because many people simply don’t know enough about them. In countries like Israel, about 60% of households have a SWH.

Solar water heating relies on the abundant energy of the sun. Although SWH systems may use an electric back-up, far less electricity is used. This means ’free’ hot water, less pollution and hot water even when there are power failures! SWH systems require little maintenance once installed and typically last 20-plus years. They will save you money and are a great asset when selling a house.

How do solar water heaters work?

SWHs are a simple, reliable technology. The systems have two main components:

  • a fat, black panel called the ‘solar collector’ through which water flows and is heated by the sun; and
  • an insulated storage cylinder where hot water is stored ready for use. The black, solar collector panels are placed on a north-facing roof and are most effective in heating water when placed at an angle of between 17 and 23 degrees to the roof. The storage cylinder may either be on the roof (a ‘close-coupled’ system) or inside the roof (a split system), but must always be above the solar collector.

Being black, the solar collector absorbs heat from the sun. This warms the water in the collector. Heated water is less dense than cold water and rises to the top of the tank, while cooler fuids are heavier and sink. Cold water in the cylinder is displaced downward, causing it to cycle through the collector where it is heated by the sun.

This ’circular’ path that the water takes is known as the thermosyphon effect. When there is no sunshine, the thermosyphon effect stops. Good tank insulation will ensure that the water inside the tank remains hot for some length of time. Most systems also include an electric back-up for days without sunlight, or when more hot water is needed by the household.

Deciding to install a SWH

SWH systems can start at anything from R3 500 (integral system) and go up to about R20 000, depending on the capacity you need. A SWH system for an average home of four people with an electricity back-up will cost in the region of R7 500 to R12 000.

If an average electricity bill in a month for a four-person family is R500, you could save around R200/month on your bill if you install a SWH. Over a year that amounts to savings of R2 400. Over five years you will save at least R12 000. You are likely to save much more as electricity prices are set to climb during the next fve years as new power stations need to be built.

This means that within five years of installation you will have paid off a R12 000 SWH. After that you are looking at pure savings on your household costs. If you need to replace your geyser anyway, then this makes even more sense. In addition to your fnancial saving you will prevent some 2 400 kg of CO2 from entering our atmosphere in just one year of installing a SWH.

The cheapest way to buy a SWH is to pay cash, or make use of your housing bond. If you cannot afford a SWH when you urgently need to replace your geyser, install a hot water cylinder that is SWH-compatible and you can install a solar collector later. A SWH-compatible geyser is generally better insulated than a conventional hot water cylinder and is fitted with additional inlet and outlet pipes for the thermosyphon effect to operate.


You may heat your water by simply using a 50 litre black bucket. The bucket MUST be clean and free of chemicals. Know where your bucket comes from. Never reuse an old bucket – rather buy a new one to heat water.

Geyser-efficiency tips

  • If your geyser, or the pipes leading from it are warm to the touch this means it is losing heat and wasting energy.
  • Insulate your geyser and hot water pipes using geyser insulation piping, or by wrapping a blanket or newspaper around them. Material batting (that lines quilts and duvets) and then heavy-duty aluminium foil wrapped around the geyser with string works well.
  • Turn geyser temperature down to 60 degrees Celsius. Maintaining the temperature at 60 degrees uses less electricity (energy) than maintaining a temperature of 70 degrees. Works best when geyser and pipes are insulated. Don’t drop it below 60 degrees for health reasons.
  • Install a timer that switches the geyser on according to the time you set it and therefore avoids heating water when you do not need it. Note: The timer is only effective if the geyser is insulated.
  • Vertical geysers are more energy-effcient than those placed horizontally.

source: SMART Living Handbook


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