Does leaving hot water tank on waste electricity?

I have a hot water tank in a cupboard. There is a switch which you have to press in order to heat the water. At present I leave the switch on so I have constant hot water. Does this waste electricty and if so roughly how much? Or would it be sensible to only switch on when I need hot water?



Update 2:


10 Answers

  • GTB
    Lv 7
    9 years ago
    Favorite Answer

    With all due respect to the first two responders, their answer is not accurate.

    The tank should be well insulated. If it is not well insulated, get it insulated as this is the waste.

    It takes a certain amount of energy to raise the water temperature to the high temp set point. As you use the hot water, cold water that enters the heater needs to be heated to keep the water hot. Turning the heater off results in deferring this required heating and you will not have hot water when needed.

    In fact in many communities, the electric utility has time of day rates for electric water heaters. When electric demand is lower and therefore cheaper to these people, electric water heaters are enabled (allowed to make hot water). When electric demand rises, these people have the electric water heaters disabled (not allowed to make hot water). Usually the water heater is enabled from about 7:00 p.m. until about 8:00 a.m. These people have no problem with this because they use little hot water during the day and the energy needed to heat the water is consumed during off peak time and the well insulated water heaters loose little to no heat in the peak time.

    Having said the above, l suggest you leave it on.

  • 9 years ago

    First of all, not such an obvious question, if you know anything about water heaters, other than the fact that there are gas and electric models, you would know that the only type of water heater that has a switch is an electric unit. Hilda said the water heater is in a cupboard, which means it's fairly small, probably less than 20 gals. These units are used in mobile homes because they can be located under kitchen cabinets and out of the way. They are also used in some new home construction for instant availability of hot water, in this case they are called "point of use" units. So, to the actual question. If you use a lot of hot water during the day, for what ever use, then leaving the unit on for that period is practical. You have the hot water available when you need or just want it. If demands for the hot water taper off during the evening hours, maybe then you could shut it down for several hours without any inconvenience. You would have to remember to turn it back on upon rising the next morning, so that the hot water is again available.

    Source(s): 40 + years of home building, remodeling, repairing, and maint.
  • nosdda
    Lv 7
    9 years ago

    The heater for the hot water will switch off the electric automatically once the set temperature is reached, then switch back on once it falls below the set temperature. To only use the heater switch when you require hot water will use more electricity as you are have to heat up the water from cold everytime, and will use more electric. It is like heating up an electric kettle when the water is already lukewarm than a kettle that has cold water. I keep mine on all the time to save electric.

    Source(s): Plumber UK.
  • 9 years ago

    First of all, obvious question, is it gas or electric. If it is electric the only time you should turn it off is if your going to not be in your home for a long period of time. Now if your in a motor home or something and you have a small tank I would say yes. But the larger the tank the more time and power it will need to heat the water up to use again.

  • 9 years ago

    I agree with GTB. You should leave it on because the w/h will work harder to heat the cold water and you will be using as much or if not more electric to reheat the water. If it concerns you that much you should consider a tank less water heater but they are expensive and you must maintenance them yearly in order for you not to default on you warranty.

  • Anonymous
    9 years ago

    If the switch is constantly on then it will be constantly using hot water. I think the amount of electricity used will be determined by the size of the tank, but don't quote me on it. It might be an idea to get a power reader which tells you how much power you use at anyone time and also how much cumulatively during the day- we got one free from N power the other day and it's quite interesting.

    We only use our hot water tank when we need hot water such as taking a bath and it take half an hour to heat up. Other things such as washing up we boil a kettle for.

  • Cheryl
    Lv 4
    4 years ago


  • KevLEC
    Lv 6
    9 years ago

    There are many factors to consider here.

    How many people live there & how much water you use,insulated tank,size etc.

    Basically the only way is to note your last bill units used,then next quarter try turning on 20-30 mins before you need it & compare both bills.

    Source(s): Lecky
  • Anonymous
    9 years ago

    Hilda, I answered this question a week ago, and you took no notice, but took time to ridicule me, and now GTB has confirmed and clarified what I told you. there is none so blind as cannot see.


  • 9 years ago

    yes quite alot. you should switch it off when not needed and turn it on when you need it you will seeing the savings on your electric

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