Electricity Saving Tips For Homes And Offices

Choose the right sized water heater/geyser for electricity saving

By on October 15, 2014
This article is also available in these languages: hi Hindi

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

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There Are 108 Comments

  1. 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.

  2. 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

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. Anuj Mathur says:

    Hi Abhishek,

    Thanks for the useful information. I do have a query with regard to the optimum capacity of the geyser I should buy. My house has two main bathrooms and a guest bathroom. Unfortunately, the guest bathroom only has a horizontal space of 13? to install a geyser. Even the vertical space is at premium and a bulky geyser would not fit there.

    I bought a havells 15 litre geyser and tried to hang it at the place of installation (without actually installing it yet). Though it seems to fit snugly there, I do feel that there wouldn’t be any clearance or margin at all, neither on both sides of the geyser, nor from the top. An experienced electrical did also advise the same thing to me.

    If I buy the 10 litre version, it should fit appropriately there. But I am concerned whether it would be sufficient. Although the bathroom would only be used occasionally, it?s likely that the shower will be used rather than bucket. Considering the cold climate in Delhi, would a 10 litre geyser be sufficient for a single person?s shower bath. Or else, do you think that it would be appropriate to install the 15 litre version. Energy consumption would not be the deal breaker here.

    An early response would be much appreciated.

    • Abhishek Jain says:

      Hello Mr Mathur,

      10 lts water heater can provide a short shower bath not a longish one which people mostly like while using shower. If there is another bathroom close to this one, you may consider going for a bigger water heater for combined two bathrooms.

  8. Jebin says:

    Kindly request your suggestion. I am trying to decide between a 3L and a 1L instant water geyser (both rated 3KW) for shower bath purpose. Per the calculations that you have explained below, for a 3L and temp difference of 30 C – time required is 6.3 secs; and for a 1L – same scenario – time required is 2.1 secs. If this is true, isn’t 1L model better?
    Based out of Bangalore and the water source is both borewell water and Kaveri water. Which brand is better – AO Smith, Racold or V-Guard or any others?

    • Abhishek Jain says:

      Hi Jebin,

      As per the calculation mentioned below it will take 2 mins to heat 3 lts and 42 seconds to heat 1 ltr by 30 degrees. The rate of heating remains the same at 3 KW. Better or not will depend on the rate at which you use the hot water. A 3 KW heating element can heat 1 lts in 42 seconds. If you are drawing 1 lts water in 42 seconds then you will get continuous hot water be it 1 ltr instant heater or 3 lts instant heater. Because the moment you draw water from the tank, cold water will fill it in.

      In general I would not suggest instant water heater for shower bath purpose specially when you live in B’lore where temperature is generally low. For shower bath in B’lore 15 lts water heater would be better.

  9. mudu says:

    I need instant water electric heater or geyser 6 or below liters because I have already instant water electric geyser but electricity billing is too high every month. Please advice good instant water electric heater or geyser for low electricity bill. We have take bucket bath every day. I live in Mumbai.

    • Abhishek Jain says:

      Hi Mudu,

      Water heater of 6 lts capacity is not classified as instant. Instants are 3 and 1 lts models. If you are looking for 6 lts you can look at these:

      Havells BUENO 6
      Havells QUATRO 6
      Bajaj Majesty 6GPU
      A O Smith HSE-SBS-006 or HSE-SAS-006

      If you are looking for instant, then you can look at Racold, A O Smith, Havells, Bajaj or Venus instant water heaters.

  10. Ashfak says:

    Ashfak from bellary Karnataka, we r 4 family members we using bucket bath which is better 3litr or 6litres plz reply.

  11. husein says:

    We want instant water geyser not storage geyser.below 6 liters. We take bucket bath.pls suggest good power saver or good star rating geyser or heater i live in Mumbai.

  12. husein says:

    I need instant water heater (which can heat at least 10 liters of water) with low power consumption?

    Please advice? I live in Mumbai.

    • Abhishek Jain says:

      You can look at these models:

      I guess Indore is quite cold in winters. 6 lts is good for places like Mumbai that are not very cold in winters. And that too for bucket bath. So if it will be used just for bucket bath and temperature is quite low in winters then a 10 lts model will be sufficient. If it is for shower bath then you will have to go for 15 lts water heater. You can look at these 10 lts water heater models:

      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

  13. kumar says:

    Hi, Planning to install water heater for attached bathroom for single(sometimes two persons) usage. WATER PRESSURE is too LOW since its a single floor house and over head tank is just above the roof. Please suggest which type of geyser I can go with

    • Abhishek Jain says:

      Hi Kumar,

      Low pressure is not a problem for water heaters. High pressure is. However a question for you, will it be used for bucket bath or shower bath?

      • kumar says:

        Thanks a lot abhi for ur reply. my concern was, since the water pressure is low, it takes time to fill up, which might cause dry heating.(during filling). Coming back to your question, usually bucket, v.rarely shower. Again low water pressure might be a drawback for using shower. It would be great if you can suggest best type n capacity for the above requirement

        • Abhishek Jain says:

          Hi Kumar,

          For bucket bath 10lts water heater should be good enough. You can look at these models:

          10 lts models:
          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

  14. Mayur Ganeriwal says:

    thanks u abhishek for suggest me..

  15. Aneesh Thomas says:

    Hi Abhishek,

    Thanks for sharing ur knowledge.. I really appreciate u for helping the unknown.

    I am Looking for a Water Heater For a Small House. I Would like to Knw, How fast a 6ltr 3000KW 5 star rated geyser can Heat Up the Water to Its Max Temp? If The Climate Temp Is around 20 Degree.


    • Abhishek Jain says:

      Hi Aneesh,

      To heat 6 lts water to 60 degrees the energy required would be 6 x (60-20) x 0.0012 = 0.288 kwh or units. So time taken would be (0.288/3)x60 = ~6 mins.

  16. Mayur says:

    hello abhishek..,
    u say dat all of them have protective inner coating technology dat prevent
    water heater from corrosion..
    can u tell me which brand is good and better .. i m confuse which product i
    ao smith comes in blue diomand glass lines technology and raccold comes in
    polytene coating technology ..
    can u suggest me which is better .. racold interno dg 25 ltr.. or ao smith
    hse -ses , or venus splash digital..
    wat is means of 1kw/2kw/3kw..
    which temperature i set to warm water dats its works for long tym and how
    many tym taken to warm the water…

    • Abhishek Jain says:

      Hi Mayur,

      Polymer based coating is better than Enamel based coating for hard water protection. You can go for Racold model.

      1 Kw/2 Kw/3 Kw means the rate at which water is heated in the water heater. 3 kW will heat fastest and 1 KW slowest.

      For 25 lts, a 1 KW heating element would take about 1 hrs to heat water, 2 KW would take 30 mins and 3 KW 20 mins.

  17. Mayur Ganeriwal says:

    I m mayur from pratapgarh u.p .. i want to buy 25 Ltr water geyser.. which is good for me.. i select three model ao smith , racold interno dg 25 ltr , venus digital splash .. here in pratapgarh water is hard…
    Is remote control water geyser is good or manual ..

    • Abhishek Jain says:

      Hello Mayur,

      It is better if the geyser has a remote control. That gives an ease to switch on/off the water heater or change the temperature settings. To reduce electricity consumption it is better that you keep the temperature of the water heater at a lower setting. The three brands that you have chosen, all of them have protective inner coating to prevent the water heater from corrosion. An enamel coated glass lined tank is good for hard water. You can choose anyone of them.

  18. Guru says:

    Thanks Abhishek,

    What the option for hardwater in 6

  19. Guru says:

    Hi Abhishek,

    We are in Pune (Wagholi) were we have Bore well and water tanker which supply water (both areHard water) i need 2 no 10L-15 L 5 star rated which can handle the hard water.

    • Abhishek Jain says:

      You can look at these:

      15 lts models:

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

      10 lts models:
      Havells QUATRO 10
      Havells OPAL 10
      Usha Aquagenie 10L
      Bajaj Majesty 10 GPU

  20. Narayanan says:

    I am from chennai I have 10 lts water heater. I think its more current consumption. I want to change to solar water heater it is good or not. pls suggest.

    • Abhishek Jain says:

      Hello Mr Narayanan,

      Solar water heater is an excellent option. However they are available in large sizes like 100 lts+. You can read more about them on this link: https://www.bijlibachao.com/solar/solar-water-heater-system-how-can-it-save-energy-and-its-prices-in-india.html

  21. Kunal says:

    I like to have longish showers 10-20 minutes and was thinking of getting a tankless geyser. Would the geyser give hour water for the entire duration?

  22. mansi upadhyay says:

    Hi,plz tel me which one is best,tank or tankless geysers????

    • Abhishek Jain says:

      I would say that it will be best if you can go for the smallest tank geyser (6 lts/10 lts/15 lts) that can suffice your needs.

  23. Sanjiv says:

    I am from Mumbai. We are a family of 6 and most of them have bucket bath. We had problems with our 20-year old “Mini Spherehot” instant water heater(in the past, had been repaired a few times for coil burnout, etc) and now that it’s out of order, would like to replace it with a new geyser. Though the domestic water supply pressure is moderate, it arbitrarily falls down to very low levels. We usually fill up about less than half bucket with hot water and then fill the remaining with cold water. Please recommend a suitable water heater(small).

    • Abhishek Jain says:

      I would suggest that you go for 6 lts water heater. You can look at these:

      Havells BUENO 6
      Havells QUATRO 6
      Bajaj Majesty 6GPU
      A O Smith HSE-SBS-006 or HSE-SAS-006

  24. Anand says:

    Hi Abhishek,

    I am Pune, Maharashtra. Temperature in winters can go below 10 while in summers it might cross 40. I have a family of 4. There are 3 bathrooms in the house, two of which are connected to single water geyser connection. One bathroom is separate.

    For the separate one, I am planning to buy a 3 ltr instant geyser and I will look for options you suggested in other threads.

    My question is about the other two bathrooms with single geyser. One of the two bathrooms would be used daily while the second bathroom would be used rarely (only when guests come). Do you think an instant geyser would be okay for such an arrangement? If no, then can you suggest an adequate size of storage geyser? both of us using the bathroom daily would mostly have bucket bath. Once in a week would be shower bath.

    Plus, I also have a constraint of height of geyser as the space provided would incorporate approx. 300 mm height of the geyser.

    Please guide.

    • Abhishek Jain says:

      Hi Anand,

      Sizing of water heater should be done based on instantaneous requirement of hot water. If at any given time only one of the bathroom will be used then even a common instant geyser would work. If both will be used together then you would need about 25 lts water heater as instant water heater will not be able to give sufficient hot water for two people.

      • Anand says:

        Thanks for the reply Abhishek.

        Since one bathroom would be used rarely, I assume there is no point in heating 25 ltrs of water everytime. (thats what I gathered from other posts in your blog.)

        Now about instant geyser, I have two points:
        1. Since we take shower bath once a week, would the instant geyser be very inconvinient? Even with a higher capacity heating element?
        2. Some of my friends in the society experience higher energy bills, which they feel is because of instant geyser. But your blog says its not the case. Maybe their bills are higher because of some other reasons? (avg bill of 1200 per month without washing machine, oven etc.)

        Based on your inputs I will decide whether to go for an instant one or a 15 ltrs one.

        Would really appreciate your reply.

        • Abhishek Jain says:

          Hi Anand,

          The amount of hot water that you can get from instant water heater will remain the same be it for bucket bath or for shower bath. If you use instant water heater for shower, it will have to be a quick shower rather than a relaxed shower bath that one tends to have while using shower. It will not be inconvenient but will be short. Or it may get longer if you do not use shower at full force and higher capacity heating element.

          Also instant water heaters cannot increase electricity bills unless you leave it on for long and/or leave the tap on.

  25. Daniyyel says:

    Hi Abhishek,

    I just bought the Racold Eterno DG 25L. It is a very slick geyser with tonnes of options – uniquely being able to set kW usage between 1/2/3. I needed some advice on what setting would be ideal for electricity savings.

    Assume the following to be true – initial water temperature in tank before heating is 20C, desired water temperature is set to 50C, and geyser will be switched on and off before bath. Keep in mind time needed to heat up isn’t an issue as far as inconvenience goes as it has an auto-start timer and I am the only user.
    a) 1kW (4 mins/deg) – geyser runs for 2 hours at 1kW to raise the temperature 30deg from 20C to 50C
    b) 2kW (2 mins/deg) – geyser runs for 1 hour at 2kW for the same scenario
    c) 3kW (1.5 mins/deg) – geyser runs for 45 minutes for the same scenario
    *The mins/deg numbers are from the manual and on basic observation (by keeping an eye on the LED display showing actual water temperature and noting it against a watch) I have noticed them to be fairly accurate.

    My question is assuming the above stated scenario, in terms of pure electricity savings, which is best? Run it at the lowest kW but for the longest duration, highest kW for the shortest time, or the middle ground.

    I hope this poses as interesting a mathematical question to you from a fellow energy geek!

    Your insight on this case and in general (that is varying start/stop temperatures, that is higher/lower differentials, etc) would be appreciated so that I may best make use of my new and very feature packed geyser (that is temperature setting, kW setting).


    • Abhishek Jain says:

      Hi Daniyyel,

      Energy (Electricity) consumption will almost be the same in all the three cases because the volume of water being heated will be the same. There will be some heat loss from the surface but that will be insignificant in comparison to total energy used for heating. Even for that insignificant heat loss, the one that heats fastest will have lowest heat loss. So a 3 kW setting would be the best. You save energy as long as you do not waste hot water or leave hot water in the water heater.

      • Daniyyel says:

        That’s rather strange then for them to label their 1kW heating option as “Eco” mode.

        I’m afraid I may have made a mistake in purchasing this one as I was under the impression given that this was the only geyser that had the option to tune the power all the way down to 1kW, it would offer the best electricity savings.

        Just for my information, would say something like the new Havells 10L/2.5kW 5 star rated instant geyser have been a better choice? Would that sort of a “hybrid” (I say hybrid because of the comparatively larger tank size) work in Kolkata? Mean average lows in the coldest months are barrel below 15C. In the last few days of use I have observed initial water temperature in the tank to hover in the mid 20s.

        Now that I’m stuck with this one what do you suggest is my best course of action to achieve maximum savings? Run it on 3kW at a temperature of 50C and switch off before showering? Could you approximate (using the values I gave you) what kind of usage (in units) per day, assuming it runs once a day, I am looking at with this geyser?

        • Abhishek Jain says:

          Hi Daniyyel,

          The heating elements of water heater are almost 98-99% efficient, i.e. whatever energy they pull from source is almost completely used up for heating the water. So if you have a 10 lts water heater then to increase the temperature by 20 degrees would use: (10 x 4.2 x 20)/3600 = 0.24 KWH (or unit of electricity). A 3 kW unit will give this much energy in 0.24/3 = 0.08 hrs or about 5 mins. A 2 kW unit will give this much energy in 0.24/2 = 0.12 hrs or about 7-8 mins. A 1 kW unit will give this much energy in 0.24 hr or about 14-15 mins. A BEE 5 star rated 10 lts water heater would have standing loss of about 0.42 kWH (or units)/24 hrs or 0.0175 unit in an hour. So if you heat water with a 1 kW heating element and use it within an hour then on top of 0.24 units you may additionally use up 0.0175 units of electricity. If you heat using a 3 kW heating element then it will get heated up in 5 mins and if you use the water in another 10 mins then you hardly waste any electricity.

          So the rating of heating element is just to speed up or down the heating. The energy consumption will increase if you increase the volume of water to be heated or if you leave hot water in geyser (loss due to standing losses).

  26. Shivraj says:

    Pls advise me for the selection of suitable Water Heaters/Geysers foe the use of family having 3 members only.
    Our average consumption of water as 15 Lit/person.

  27. Sidharth says:

    Confused which type & size geyser to buy. We are a family of 4 assisted by two helpers. This geyser is for Kitchen & water will be used for utensil cleaning, mopping & water for two assistants to take bath. May be 1-2 bucket for gaurd & Driver. Please suggest which is the best buy. Thanks in advance

  28. sharad says:

    We had 4 members family. Only I use showers. i need a water geyser for bathroom. Which size i should go for ?

    10L or 15L ?

    • Abhishek Jain says:

      You can go for 10 lts model.

      • sharad says:

        Does 10L will provide continuous hot water supply even if initial 10L got used ? if yes then how much Ltrs hot water i will get continous ?

        • Abhishek Jain says:

          A water heater typically heats water to a peak of 60 degrees (unless you adjust the thermostat). Which means if the incoming water temperature is 25 degrees, then 10 lts water will use up 10 x 4.2 x (60-25) = 1470 kJ of energy. Typically human beings can handle only up to 40 degrees hot water. So the amount of water that can be adjusted to 40 degrees with that about of heat is = 1470 / ( (40-25) * 4.2 ) = 23 lts.

          So if the incoming water temperature is about 25 then with 10 lts water heater you can get 23 lts of hot water at 40 degrees (which is decently hot). A regular shower bath takes up 25 lts (unless you are used to having long shower).

          • sharad says:

            Well said. Thanks a lot for your valuable support.

            What happens after 23L hot water ?

            i am confused between 10L and 15L as i heard more capacity takes more time like 15L takes 20min while 10L takes 12min to heat water

          • Abhishek Jain says:

            If the water heater is switch on, it will continue heating the water. But it will not be able to heat the water to temperature that you need. You will have to wait for it to heat the water to the temperature you need. Certainly 10L will take less time to heat, but the total volume of hot water (at temperature at which you need) will be less as compared to 15L water heater. However if you go for bigger water heater and leave hot water in it, the water will loose heat with time and in turn the electricity used for heating goes waste and thus we suggest going for smaller sized water heater.

  29. Anil says:

    So what do you suggest? This article is basically talking about storage water heaters not instant water heaters.

    What do you suggest for instant water heaters?

  30. Avishek says:

    Shall we shut down a geyser once we have enough water for future use? Or it is fine to keep the geyser on even after cut off is reached? Which one is better efficiency wise and what are the advantages/disadvantages of both? Thanks.

    • Abhishek Jain says:

      It is better to switch off the geyser once you have enough water for use. Keeping it on you would waste electricity in form of standing losses.

  31. Geetansh says:

    I want to fit a geyser in my washroom, which is for small family – 4 persons. I can fit a gyser of physical size – length 3 feet. Could you please suggest which gyser would best fit in my requirement. Also please let me know the capacity, brand and model of your suggested geysers. Thanks for your help!

    • Abhishek Jain says:

      Hi Geetansh,

      Is the constraint height or length. If it is length then you can go for vertical models like Havells Quatro, A O Smith HSE-SAS/SBS/SDS/SES models, Racold Eterno/Altero models, Bajaj Majesty GPU models. If it is height then you can look at Bajaj GMH RF or CP models or AO Smith EWSH model.

  32. Anuj Seth says:

    I do not afree with your point of switching off the Geyser. I have noticed if we keep the Geyser on it saves electricity. Because the water inside the geyser is still at higher temp. than the input water temp. So The energy used to heat that water to 60C will be less than what you will use next day.

    These day we get Geysers which have good insulation and keep water hot till next day will less electricity.

    • Abhishek Jain says:

      The most efficient BEE 5 star rated geysers also have standing loss. So with best of insulation there is loss of heat. It’s better to avoid that.

  33. P.Srinivasakumar says:

    What can be the maximum efficiency of the normal geysers?

    • Abhishek Jain says:

      The energy efficiency of geysers is mentioned in kWH of standing loss per day. Which means the amount of energy it will loose in the whole day if hot water is left in the geyser. The numbers differ for different sizes of geysers. Smaller geysers have low surface area so the loss is less, bigger geysers have higher surface area so the losses are more.

  34. Sander Vandenhaute says:


    Do you have any detailed, statistical information on the (hot) water usage of an average indian household (so not just 5 en 10 liters but like 6.231 and 9.345)?


  35. anikethan says:

    If i have a solar water heater, and there is an overcast in rainy season, How should i route the water from solar system through the geyser and what type of geyser should I buy

    • Abhishek Jain says:

      Hi Anikethan,

      There are two types of systems available in market: 1) Hybrid: which is a pre-integrated system. 2) Simple solar water heater with no integrated electric geyser. However in the hybrid system, the hot water output from solar water heater is put in the electric geyser. Electric geysers have thermostat which shuts off the electricity once the water reaches a certain temperature. This ensures that water is always hot to a certain degree. Now if you want your solar water heater to be integrated to your geyser, you just need to ensure that the piping in your house is such that the hot water output from solar water heater goes into the electric geyser (which can be any regular electric geyser). If the water is hot enough, then the electric geyser will not consume any electricity (thermostat will keep it off). If water is colder then the electric geyser will heat it. So you just need to ensure that the piping is such that the water from Solar Water heater goes into the regular geyser.

  36. KP 7 says:

    good helped a lot.

  37. vijay says:

    Very useful points.

  38. Dnyanesh Bodhe says:

    Ver Very well written.. excellent initiative…!

  39. aravikumar says:

    Excellent info guys. Very helpful & well-written. Keep up the good work.

  40. Abhishek Jain says:

    Hi Anuradha,

    We wrote about solar water heater on one of our posts: https://www.bijlibachao.com/solar/solar-water-heater-system-how-can-it-save-energy-and-its-prices-in-india.html . Do check it out and let us know if you have more questions.


  41. anuradha says:

    Hi abhishek,
    Could you please tell me the cost saving a 100 litre solar water heater would give in a period of two years as compared to a normal geyser of 100 litre.

  42. furnace Rochester NY says:

    This is really going to help me in the related stuff..thanks for the information

  43. Piyush Agrawal says:

    Hi Abhishek, I have many questions related to all electric equipments that is required in hotel like T.V., A.C., Geyser, Fan, lights, invertor, batteries, solar power etc. Let me know if I can post my questions here / can email you / call you.

    piyush0101 @ yahoo . com

  44. Piyush Agrawal says:

    I am starting a 2* hotel of 30 rooms. Can you please recommend which geyser is good & what should be the size. Based on my understanding after reading the article above, I think one geyser per room, storage type water heater & size of 10L, should be good enough.


  45. krishna reddy says:

    What is Cp Used in calculating units? Is it specific to heater?

    • Abhishek Jain says:


      Cp here refers to specific heat of water and it is no where related to the heater. To calculate ideal units, you can use this simple formula:

      Ideal Units = Volume of Water x Temperature Difference x 0.0012


      • krishna reddy says:

        Thanks Abhishek, Yours work is truly appreciated. As you said ideal units, few more units get added depending upon standing loss. Lets say I’m using 15lts Kenstar water heater, as you mentioned in some other article, How long does it take to get to 60c temperature(winter season) after I switch on. Standing Loss is loss one it’s heated and left being unused, am I right? What If I use heated water immediately after switching off heater, there wont be any loss right? would the above geyser automatic switches off once it reaches 60c? will it keep heating for standing loss, if I switch on?

        • Abhishek Jain says:

          Let me try to answer your questions one by one:

          1) Assuming that the temperature of cold water in winters is 20oC. The units needed to heat water will be 0.72 units (calculated using the formula mentioned earlier). Now if the water heater is rated at 2 kW (or 2000 watts) then it will take 22 mins to heat up, if the heater is rated at 3 kW (or 3000 watts) then it will take 14 mins.

          2) Your understanding is right, standing loss is heat loss once the water is heated and left unused.

          3) Your understanding is right that if you use heated water immediately after switching off the heater, there will not be any loss.

          4) Most modern water heaters have thermostat which will switch off the heater once the temperature reaches 60oC. But if you leave the water unused and water heater switched on for a long time, the water will loose heat (standing loss) and the temperature will come down and then the heater will start again to maintain the temperature to 60oC. So effectively if you leave the water heater switched on for the whole day, then the electricity consumed will be Ideal units for heating the water + standing loss.

          Hope this helps.


  46. sneha says:

    even using induction heater you can get hot water right ..???? then why geyser ?? geyser is more efficient than induction heater but in what way..????

    • Abhishek Jain says:

      Geyser is more of an enclosed space which is well insulated. The heat exchange with the environment is very less thereby most of the energy given is used up to heat the water. And the hot water does not lose much heat.

      Whereas water heated with induction heater is in direct contact with air and can loose the energy when in contact with air. The water is not insulated.

      Although if you really heat the water immediately and use it, I do not think even induction heater would be much inefficient. Geyser has the benefit that you can keep the hot water stored. Also with geyser you can use the water in multiple taps and showers.


      • hanmant says:

        Hey hi,
        for hot water what should I prefer electric geyser or induction stove.

        • Abhishek Jain says:


          Better than induction stove, I would suggest that you use an instant water heater. Although it is always better to use a small sized storage water heater (10-15 lts) and switch it on before use and switch it off as soon as water is heated.


          • manoj says:

            Hi Abhishek,
            If one really has to save electricity to the tune of 80%, one should use air source hybrid heatpumps. Its much more reliable than solar and you get 24 hrs hot water. we have been giving this solution to Hotels, Hostels , Paying guests since a very long time and they recover their investment in less than one year.
            Induction heating water heater is also ready with us now for domestic use. We have been in water heating for 40 years with constant new technologies. We can also heat swimming pools at only 10-15% of normal expenditure having done more than 200 such installations.
            Please contact us at [email protected] based at bangalore

          • Abhishek Jain says:

            Thanks a lot for the information Manoj. We will surely research about it and will contact you for more details.