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Does lowering the water heater geyser temp save power

  1. Jul 9, 2012 #1
    If a water heater geyser(15 lit) set temp is dropped down does it help in saving power.

    I open both tap hot water and supply water simultaneously to my bucket for bathing purpose only. So if the temp is set high(as set by the company), it will be needed less and therefore less water is to be replaced and heated again to bring back to its set temp.

    On the other hand if the temp is set at lower temp, more water would be drawn from the geyser and hence more water is to be replaced and heated again in this case to bring back to the set temp but definitely to an lower temp.

    Which one is less power consuming?


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  3. Jul 9, 2012 #2


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    I believe a lower temperature will save energy because losses from the tank will be lower.

    However beware of the potential for legionnaires disease if the temperature is below 60C.
  4. Jul 9, 2012 #3


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    Setting your heater to a higher temp will mean less water, but more energy needed to heat that water, so I don't think you save anything either way in regards to the amount of water used vs temperature. The increased temperature will lead to greater heat transfer between the water and the outside of the tank, which is the primary reason for the power savings for most people when they lower the temperature setting. Ideally you would want to heat the water coming in to the temperature you wanted it at and then use it immediately, like a tankless water heater does.
  5. Jul 9, 2012 #4
    Thanks for the warning on legionnairies disesase, its really true. My geyser doesn't have temp mark, so I would better keep close to the max mark.
  6. Jul 9, 2012 #5


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    The main problem with using a high temperature in you heater is the loss of energy whilst the water is not actually being used - i.e. when the heater sits on the wall for hours and no one washes. To be fair, they tend to be quite well insulated but they are constantly losing heat and that loss is proportional to the temperature difference between the water and the room. So the answer to your original question is yes, you can save on wasted energy by using a lower temperature.

    Legionella is a potential problem but there is a lot to be said for storing the water at a temperature that you need for use. However, you can get yourself a larger quantity of water at the wanted temperature if you store it at high temperature and then mix cold with it.

    There are Health and Safety situations where the maximum allowable temperature for hand washing is below that for preventing Legionalla. Catch 22. I guess the solution is to have an thermostatic mixer tap on the output of the geyser. An expensive solution. Or you could increase the temperature for a period every night to purge the bacteria. Now, I reckon I could sell that one. (Now, someone tell me it's done already)

    Did you think of doing an experiment? Run the heater at different temperatures (lights and everything else turned off) for a couple of hours under both conditions and read 'the meter'.
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