Mythbuster: Does It Use More Electricity to Leave Your Geyser on, or to Switch It Off When You Leave in the Morning and Switch It on When You Get Home?

Mythbuster: Does it use more electricity to leave your geyser on, or to switch it off when you leave in the morning and switch it on when you get home?
Abstract: To test whether if it is wise to leave your geyser on or switch it off in the morning and back on in the evening. In this report, a test was done and the results were evaluated and analysed. It was found that indeed switching off the geyser for the duration of the day results in decreased heat consumption.

CE Database subject headings: geyser; power; heat loss; electricity consumption.


The efficient usage of electricity is becoming more of a world issue due to increases in carbon emissions and other related factors which in turn tend to be affecting the electricity tariffs both directly and indirectly. This high tariff problem has led to some suggestions or solutions rather, that will ensure that electricity is used efficiently. One of the solutions proposed is in switching geysers off after use in the morning and back on in the evening when one gets back from work.

Method and Materials

Three Logik kettles were equally filled to the maximum (~1.7 L) and set to on. The time that the water took to boil was measured using a stopwatch and the temperature at the boiling point was took and found to be approximately 94°C. Kettle 1 was left to cool and the readings of the temperature were taken every 5 minutes for 30 minutes. Kettle 2 was boiled every 5 minutes; with the temperature read on the boiling point (immediately just after boiling) and the time took to boil was recorded. After 30 minutes kettle 1 was re-boiled and the time it took the water to boil was recorded. Kettle 3 was used to fill kettle 1 should the volume change be significant.


During the experiment, experimental data was taken and is as follows:

Table Results for the experiment.

Table 1.Kettle 1,Water boiled every 5 minutes

No of times boiled 0 1 2 3 4 5 6
Time taken (Sec) 307.2 43 35 33 30...