Admittedly, it’s a popular myth that switching off your geyser saves electricity as Gareth Cotten discussed in How to save on your electricity bill and it’s even propagated by government, but it’s completely false and it’s inexcusable that a reporter does not check his facts before claiming a cited obvious, but bogus method of saving electricity. The fact is that in a properly insulated geyser the heat energy is well contained and the only possible source off loss is the tiny amount that escapes the insulation during the day. While the geyser is on during the day and no water is consumed, a small amount of electricity is used to replace this heat loss – the thermostat typically switches on for two minutes once every two hours (measured on my own geyser) representing a daily extra consumption of around 50 Watts or around R30 of energy costs a month! Anything you do to a geyser can only save a fraction of this amount – the rest is actual energy used to provide hot water actually consumed and you cannot do anything about that.
The fact is that by switching off the geyser, water is allowed to cool further than usual so that when you switch it on again, it takes as much energy to reheat the water to its original temperature than it takes to keep it at that temperature in the first place – it’s called the law of conservation of energy and is an inviolable law of nature. What confuses the matter, is that a small saving is actually possible because the rate of heat loss falls as the water cools – this is, however, a second order effect that on a daily cycle has almost no effect. If you leave the house for a few days, yes – because once the water reaches room temperature there can no longer be any energy loss. I have carefully measured my own geyser behaviour (family of six) using an electricity power data logger – the saving is at best about 2% if you switch the geyser off overnight. This is supported by studies done at the University of Pretoria, available to any reporter. The best you can do is buy a geyser blanket and even with that the small savings you make it will take about a year to pay for the cost of the blanket.
*Arnold Theron is an engineer and member of the Moneyweb Community