Electricity Saving Tips For Homes And Offices

Choose the right sized water heater/geyser for electricity saving

By on April 19, 2015

Planning to buy a new water heater/geyser and confused with the options available and sizes available? If yes then you are not alone, there are many people who face the same situation while buying a water heater. While buying a water heater one has to make sure that it not just suffices the need of the family but also does not increase electricity bills (or units consumed) significantly. People might look at the wattage of the water heater to determine the amount of electricity the water heater might use, but wattage does not have any impact on the electricity consumption of water heater. We will try to list some facts that can help you decide on the size and type of water heater.

Water Heater

What factors does electricity consumption of water heater/geyser depend on?

Electricity consumption of water heater depends on:

  • Volume of Hot Water used: This is the main driving factor of electricity consumption by water heaters. The more the hot water you use, the more the electricity it will consume.
  • Tap (Input) water temperature: Places with colder climates need lot more heating than places with warmer climates. A water heater in Kashmir will require lot more electricity than a water heater in Tamil Nadu.
  • Temperature of water used for bathing: Please note that this is different from thermostat temperature.
  • Thermostat temperature: This is by default set to about 60oC for most water heaters. Some heaters have external control to change this setting.
  • Standing Losses: Yes, water heaters do lose heat and this is calculated as standing loss. It is the heat lost through the surface of the water heater. BEE defines standing losses as the energy consumption of a filled water heater, after steady state conditions have been reached when connected to electrical supply, when no water is drawn. Much of this depends on the quality of material used for making the water heater. Branded water heaters are of better quality and thus they are preferred. BEE also rates only the branded water heaters.

How much water is required for my family?

A very straightforward guideline for the same is as mentioned below:

  • For bathing using bucket water: 15 lts/person per bath (one bucket). If more buckets of water are used, then add 15 lts/bucket.
  • For bathing using shower: 25 lts/person per bath.
  • For tub bath or extended shower bath: 35 lts/person per bath.
  • For washing cloths: 10 lts/person per day.
  • For washing utensils: 5 lts/person per meal.

(Source: http://www.teriin.org/ResUpdate/reep/ch_9.pdf)

So if there are 4 people in the household and all 4 take shower bath. Then the total hot water requirement per day of the household is 100 lts. Keep adding the water per use as per the guidelines above and you will get the water requirement of your house.

What is the ideal temperature for bathing?

Although most water heaters have a thermostat setting of 60oC, which means that, the water is heated up to 60oC but can human body handle water at 60oC? The answer is NO. Water at 60oC is too dangerous for human body and can cause first-degree burns. Human body temperature is 37oC and any temperature above it feels hot. A temperature of 46oC is quite hot but far less dangerous than water at 60oC. So even though your water heater heats the water to 60oC, you need to add extra cold water to make it bearable.

(Source: http://www.telegraph.co.uk/health/3318578/So-Mr-Prescott-how-hot-should-my-bath-be.html)

So what is the ideal Electricity Units that are required by your family?

Heating of water is a classic thermodynamics problem and has a straight forward formula:

Heat required = M (Mass of water) x Cp (Specific heat of water) x delta T (Difference in starting temperature and desired temperature).

A simplified solution to calculate electricity units is:

                                    Ideal Units for heating = Volume of Water x Temperature Difference x 0.0012

So if your family’s water requirement is 100 lts of hot water per day and you prefer to use water at 40oC and your tap water temperature is 20oC. Then the ideal units for your water heating requirement is:

                                    100 x (40-20) x 0.0012 = 2.4 units per day.

Will all water heaters consume ideal units of electricity?

No. The amount we calculated above is the ideal units and not the actual units. The actual units depend on the size of water heater, standing losses and the way you use it. The bigger the size of a water heater higher are the standing losses, because more is the surface area. Typical 100 lts water heaters have standing losses of more than 1 unit/day, 70 lts water heater is close to 0.9 units/day, and it decreases as the size decreases.

If you leave the water heater on throughout the day then you certainly loose the full standing loss units in a day. The way to minimize it is by heating the appropriate amount of water that is required which can be done by switching the water heater on before use and switch it off after use. This way the standing losses will be minimized to the period when water heater is used. Also do not waste any extra hot water because that is waste of electricity.

So does it mean that you should buy smallest volume water heater?

Depends. If the water heater is too small then the amount of hot water (even if it is at 60oC) will not suffice the need of single person (even after adding cold water). You will have to wait for longer for the water heater to heat the desired amount of water or keep the output flow of water from the heater low.

So what is the ideal size?

Ideal size of water heater should be close to the volume of hot water required at one go. If people take bath one by one and use 25 lts of water, then a 25 lts or a 15 lts of water heater will make sure that the water is optimum hot when one goes to take bath (at places where tap water temperature is not too low). If the tap water temperature is too low (especially in cold places) only a 25 lts capacity hot water will work if 25 lts of water is required for a bath. If water heater is connected to 2 bathrooms then ideal size is 25 + 25 = 50 lts, because 50 lts of water can be used simultaneously. This does not mean that 6 lts water heater will not suffice; it’s just that it will take more time to heat the same amount of water or you might have to bear with cold water at the end of your bath. Ideal sizes are those that generate enough heat that are good for maximum instantaneous use.

How does the wattage of water heater effect?

Wattage of water heater makes the water heat faster or slower. If you buy an instant water heater of 4.5 kW the water will heat faster than a water heater of 2 kW. At times a 4.5 kW instant water heater can also heat the water required for bathing and can save electricity (by stopping wastage of extra hot water). The only downside of 4.5 kW water heater is that it increases the electricity load of your house which means that you connected load will have to be increased which may increase the fixed charge component of your electricity bill.Infographic11


Have a question? Leave a message below (for faster response please leave a message here and avoid email or social media). We work from Monday-Friday 10 AM-7PM. Responses will be a bit delayed on other days.

There Are 116 Comments

  1. Pradeep says:

    Mine is a family of six living in a place where the average winter temperature is 5 degree. Considering 2 buckets (hot + cold) per person for a bath, can you suggest a couple of models along with the required capacity. I prefer storage type.

    • Bijli Bachao Team says:

      A bucket of water is about 15 lts. A bucket full of water at 75 degrees when mixed with bucket full of water at 5 degrees would get you 2 buckets full of water at 40 degrees. Which will be more than enough for your need. So you should go for a 15 lts water heater. You can look at these models:

      Havells QUATRO 15
      AO Smith HSE-VAS-015
      Havells PURO 15
      Bajaj Majesty 15 GPU
      Racold Eterno dg 15 lts

  2. Pradeep says:

    Is it possible to use solar water heater in early morning where there is no sunlight ?

    • Bijli Bachao Team says:

      Hi Pradeep,

      As long as the atmosphere is hot outside the water heater can heat water. Also the water that got heated previous day will stay hot in the water heater because the water heater will have good insulation.

  3. monika says:

    1 KW input then what is output KW of Geysers.

    • Bijli Bachao Team says:

      For electric geysers 1 KW input will give 1 kW output. It’s only with geysers of heat pump type that 1 kW input can give 3-4 kW output.

  4. shashi says:

    I had downloaded a doc from ur website which had details about Geyser,
    Ranking Brand Star Rating Grand Total
    5 4 3 2 1
    1 RACOLD 30 20 1 8 0 59
    2 V-GUARD 21 9 4 2 0 36
    3 AO SMITH 21 8 0 0 0 29
    4 VES-STAR 20 0 0 0 0 20
    5 CROMPTON GREAVES 18 7 13 1 0 39
    6 HAVELLS 18 1 1 0 0 20

    Based on this I had opted for V GUARD ,but in most of ur reply either u suggest Racold or Havells ,is their any particular reason for this. I stay in Bengaluru, we are family of 3 and I had opted for 10 liter Geyser, we had connected solar heated water to Geyser ,

    • Abhishek Jain says:

      Hi Shashi,

      The list of top brands is based on number of energy efficient models listed with BEE (which is based on standing losses of various water heaters). When we suggest models we look at technology and features in various models and suggest accordingly. Models from Racold, Havells and AO Smith have nicer features that can save electricity, provide protection and are durable as well. However that does not mean VGuard is bad, but if we compare models on features, models from these brands come out better.

  5. Rajesh says:

    Pls suggest between 10L racold eterno 2 vertical versus Bajaj majesty GPU 10L heater…which is better to purchase

    • Abhishek Jain says:

      Racold Eterno 2 is giving more warranty. So I would prefer that.


      I live at Bhubaneswar having a family of 3 members. We are used to bucket water bathing. Please suggest me whether am instant geyser (1 lt or 3 lt) will serve our purpose or a storage type will be better ? If storage type, then what is the ideal capacity ?? 10 L or 15 L ??? If I purchase from JAQUAR (HSE-SCJ 10 L or 15 L), is it OK ???? Or any other better manufacturers ? Kindly guide me.

      • Abhishek Jain says:

        Hello Mr Sahu,

        Bubaneshwar is not very cold in winters so even 3 lts instant water heater would work if used for bucket bath. If you go for storage then 10L one would be more than enough. Bajaj, Racold, AO Smith, Havells, Venus are some good water heater brands. If you are looking for instant water heaters then you can look in one of them. If you are looking for 10 lts water heater then you can look at these:

        Morphy Richards Salvo 10L
        Havells OPAL 10
        Usha Aquagenie 10L
        Bajaj PX 10 GLR
        Havells BUENO 10
        Bajaj Majesty 10 GPU
        AO Smith HSE-SBS-010

  6. Rajesh says:

    Sir, we r a 6-member family in Nashik. All r using bucket bath. Planning to buy Racold Eterno-2 storage water heater.
    Please suggest proper size (10L or 15 L) for lesser electricity consumption and alternate better models.

  7. Abhijeet says:

    Sir. I want to buy a Geyser for my Family in which there are 5 members. which is best suitable and which is energy efficient GEYSER?. which is best 10 Liters 15 liters or 25 liters. Please Guide me. And Prefer best Geyser.

    • Abhishek Jain says:

      Hello Mr Abhijeet,

      Which city are you in? Also do family members prefer bucket bath or shower bath? Is it only for one bathroom?

      • Abhijeet says:

        sir, my village is Naldurg which is near to solapur city. family member prefer both as shower and bucket bath. and there are two bathroom. as one is use for all and one is attached to the master bed-room.

        • Abhishek Jain says:

          Hi Abhijeet,
          You should go for 15L water heater for both the bathroom.
          You can look at these 15L water heaters.
          Havells QUATRO 15
          AO Smith HSE-VAS-015
          Havells PURO 15
          Bajaj Majesty 15 GPU
          Racold Eterno dg 15 lts

  8. joseph says:

    Is 10 litre water heater good for a shower for one person pls?

    • Abhishek Jain says:

      Depends on the city. If it is not too cold then it will surely work. If you live in a cold city and take longish showers then it may not.

  9. Bhargav says:

    We are a family of 2 adults and 1 child. We stay at Bhavnagar, gujarat, India. Which size geyser suits us most ? We get municipality water. We want to use it for shower or bucket bath either way. Thanks.

    • Abhishek Jain says:

      You should go for 15 lts water heater. You can look at these:

      Havells QUATRO 15 (Havells Quatro Digital has a remote control as well which can be quite useful)
      AO Smith HSE-VAS-015
      Havells PURO 15
      Bajaj Majesty 15 GPU
      Racold Eterno dg 15 lts water heater.

    • Deshpande says:

      Abhiji in 1ltr 4.5 kq model is available will it HV more pier consumption?or for bucket bath 1ltr 3kw will suffice in pune for countinous stream bucket bath?

      • Abhishek Jain says:

        Hello Mr Deshpande,

        power consumption depends on the volume of hot water you use. It does not depend on KW of the geyser. KW just determines the speed at which the water becomes hot. A 4.5 kW instant water heater can provide more continuous hot water as compared to 3 kW water heater. However if you put a 4.5 kW water heater, make sure that you have enough connected load on your electricity connection to handle the same.