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How to cut your geyser's electricity costs

The geyser is usually the biggest single user of electricity in a South African home. A few low-cost changes cut what it uses without giving up hot water. Here is what works, and what you must leave to a registered plumber or electrician.

Why a geyser uses so much

An electric geyser is a large insulated tank with an element like a big kettle's.

• Heating water takes a lot of energy. Heating a full 150-litre tank from cold tap water to 60 °C takes about 8 kWh.
• The tank and pipes lose heat all day and night, so the element switches on even when nobody uses hot water. An old geyser with no blanket in a cold roof can lose 2 kWh or more a day.
• Every hot shower, bath and sink of dishes brings in cold water that must be heated again.

Set the thermostat to about 60 °C

Many geysers are set hotter than needed, sometimes 70 °C or more. A hotter tank loses more heat, scalds more easily and costs more.

About 60 °C is the usual advice. It is hot enough for washing and limits the growth of harmful bacteria in the tank. Do not go much lower than 55 °C.

The thermostat is inside the geyser's electrical cover, next to live wires. Do not open it yourself. Ask a registered plumber or electrician to check and set it.

Fit a blanket and lag the pipes

A geyser blanket wrapped round the tank cuts the heat it loses, especially on an older geyser in a cold roof. It must not cover the thermostat and element cover, the pressure valve or any labels.

Foam lagging on the first 1 to 2 metres of hot pipe from the geyser stops heat leaking along the pipes.

Roof spaces are dangerous: there are falls, heat, wiring and ceiling boards that cannot take your weight. Many households ask their plumber to fit the blanket and lagging.

Use a timer, or the switch at the board

A geyser timer switches the element on only at set times, so the tank is not kept hot all day while nobody needs it. It must be fitted by a registered electrician, who gives a certificate of compliance for the work.

Set the on times shortly before the household needs hot water, for example early morning and late afternoon. A well-insulated tank stays hot for hours after the element switches off.

If you have no timer, the geyser switch at the distribution board works as a simple manual one. Switching the geyser off there is safe. It is also worth doing before you go away for a few days.

Use less hot water

• Take shorter showers, and fit a low-flow shower head.
• Wash dishes in a basin, not under a running hot tap.
• Fix dripping hot taps.
• Wash clothes in cold water.

Know the signs of a geyser leak

If a geyser bursts, switch it off at the board, close the water supply, keep clear, and call a registered plumber and your insurer. Geyser installations and repairs need a plumber registered with the PIRB, and a certificate of compliance.

This article is based on Chapter 4 of Cutting Your Electricity and Water Bills, which includes timer schedules and worked savings.