Electricity Saving Tips For Homes And Offices

Should you buy instant water heater for your bathroom?

By on April 22, 2016

One of the most common question, related to water heaters, that is asked by readers of Bijli Bachao is: “Should I buy an instant water heater for my bathroom?”. We have frequently received this question since the time we published an article stating that Instant Water heater is the best to save electricity. We have always replied to people that: one should use instant water heater only for small uses like for wash basins and kitchen, however in this article we will provide the detailed analysis of why it does not make sense to buy instant water heater for bathing.

What is Instant Water Heater?

First let’s get the definition right. Instant water heaters are those that have small storage capacity (3 lts or 1 ltr) and high heating rate (3 kW or 4.5 kW). Water heaters having storage capacity more than 3 lts are categorised as storage water heaters. The reason they are called “instant” is because due to low storage volume and high heating rate it can provide hot water “almost” instantly. But how fast is this instant as compared to your requirement? Let’s check it out.

How much time does Instant Water Heater take to heat the water

We did an analysis of minimum winter temperatures across the country and saw that the temperature of water in winter can be between 4oC and 21oC (it cannot be lower than 4oC as it will become Ice) depending on the city where you live.

Taking this into consideration we did some calculations to find out how much time an instant water heater will take to heat the water to high temperature (of about 60oC) and useful water temperature (of about 39-40oC which can be used without mixing cold water). As per our calculations an instant water heater would take about 1 minute on an average to heat water to useful temperature and 2 minutes to heat to high temperature.

The best case scenario is when a 1 ltr water heater with 4.5 kW heating element is used in a city where peak winter temperature is 21oC. And even in that case time taken to heat to useful water temperature is 20 seconds.

Flow rate of water from taps and shower

Typical taps have a flow rate of 3 lts/min and showers have a flow rate of 8 lts/min on an average. These numbers may vary with tap or shower type and even with water pressure. High end taps/showers (like rain shower, etc) may consume lot more.

Are instant water heaters really useful for bathing?

If we take lowest flow rate of 3 lts/min then the only scenario (of instant water heater) which can work is when you are in a city where peak winter temperature is 21oC and you have a 1 ltr water heater with 4.5 kW heating element. Only then will you get continuous hot water at useful temperature. And this is the only scenario when instant water heater can work. In all other cases it cannot.

So to really answer the question: “Are instant water heaters really useful for bathing?”, the only response that we have is: “No, Instant water heaters are not very useful for bathing.”, and this answer is good in most cases, unless you are fine with waiting for a few seconds for the water to heat up again. Which may be possible if you are taking a bucket bath, but if you are planning for a shower bath, be ready to be disappointed if you use instant water heater.

When can you use instant water heater?

Instant water heaters are good for places where it is needed just for hand wash or small water use. It can work great if you plan to use it in your kitchen. Anywhere else where the usage of water is more, you should go for a bigger storage water heater (6 lts or above).

Is 6 lts water heater instant?

Many people confuse 6 lts water heater as instant water heater. It is not classified as instant water heater. And the reason for that is that time taken to heat water increases as the size of water heater increases, and thus they are not classified as instant water heaters.

Are Gas Water Heaters instant?

Gas water heaters are better than electric instant water heaters as they have much faster heating capacity. And yes they certainly are instant.

If you really want instant water heater for your bathroom, then the best option that you have is to go for gas water heaters. Electric instant water heaters will not work in most cities in India.

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  • Kunal

    Hi Abhishek,
    For my independent house in Bangalore, I am planning to install shower panel which requires pressure pump near overhead tank. My need is to have high pressure for hot water too because we mix hot and cold water throughout the year in Bangalore. Initially I had planned to put a non-pressurised solar water heater along with storage geyser. However, my plumber recently told me that I need to install pressurised solar water heater instead. I am fine with installing later even though it is expensive but wasn’t sure if the pressure coming out of the storage geyser which in turn will take water from pressurised solar water heater will match the pressure of cold water or not. Does storage geyser maintain the pressure coming from pressuired solar water heater. Also I am planning to have the control/swtich for the pressure pump in my bedroom so that I can put it on when needed. Please address my questions above.

    • https://www.bijlibachao.com Abhishek Jain

      Hi Kunal,

      If you will be taking water from storage geyser then you should put a pressure pump after the storage geyser. I do not see a need of going for pressurized solar water heater. Because pressure from solar geyser will not match the pressure from storage geyser. You need pressure from storage geyser and not really from solar geyser. So you should go for regular solar water heater and add a pressure pump after the storage geyser.

  • mksng

    Hello Abhishek,
    I want to install a Instant heater for a family of 3, in Bangalore for bucket bath. Please suggest is 1ltr instant heater is sufficient? I have space constraint to install Gas heater. Thanks for any suggestion.

    • https://www.bijlibachao.com Abhishek Jain

      Instant Geyser is not good enough for bucket bath. You will have to either go for a 6 lts or 10 lts water heater. 1 and 3 lts would not be good enough.

  • Prashant

    Hi Abhishek

    I need a water heater for taking bucket bath for my family of 3 persons. I live in Chandigarh where min temperatures in the morning can go as low as 3-4 degree Celsius. Do you suggest an instant heater of 3 ltrs or a storage water heater? Please tell about the capacity required for storage one which will be suitable for my family.
    Which brands should I consider?

    • https://www.bijlibachao.com Abhishek Jain

      I would suggest going for 6 ot 10 lts water heater for bucket bath. And Chandigarh is too cold, so 10 lts would be safest. I do not suggest going for instant geyser. If you really feel the need of instant geyser then go for a gas geyser which can give you good volume of hot water quickly. A O Smith, Racold, Ferolli, Morphy Richards, Havells, Bajaj, etc are some top brands.

  • Vishal Khialani

    Hi Abhishek,

    Firstly, congratulations for writing so many useful articles for the Indian consumer in mind.

    My Problem Statement : In my house I have 6 people who use the water heater for taking a shower / bucket bath.
    Due to lack of discipline I some times find the heater is on for half an hr to sometimes
    an hr on a daily basis and no one is using it. All the 4 water heaters in my house are old and I need an upgrade.

    My Proposed Solution: In your article you had raised a point that if you one wants to take a shower then the
    output needs to be at 25 liters a min. To address this concern I am thinking of buying the evo instant water heater
    which can work at 11.0 KW. This should ensure the water is hot enough and is at enough speed for my family to
    take a shower if they please.

    U can read product here or visit amazon for flipkart.


    I do not have any budget restrictions for fixed assets.


    Please advice your thoughts

    Thank you,

    • ATANU DE

      You may like to use AO Smith Air 2 heat storage geyser, which’ll be around 3x efficient than conventional ones

    • https://www.bijlibachao.com Abhishek Jain

      Hi Vishal,

      11 kW system is huge!! With 4 such water heaters, your total load in the house will increase to 44 kW at least. Electricity department will have serious issues with that. You may check more on that on this link: https://www.bijlibachao.com/water-heaters/instant-water-heater-geyser-may-be-good-for-individual-but-bad-for-system.html

      By the way your connected load will have to be increased significantly. You will also have to check if wiring in your house can handle it. As 11 kW system will draw about 50 Amp current each. It will also be a risky proposition because at such high current, if anyone gets a shock it would be really dangerous.

    • Ashok Sinha

      What is load required for a 1 BHK flat having all basic equipment s. TV fridge Ac, cooler,gyser,micro waive,washing machine etc.

    • https://www.bijlibachao.com Abhishek Jain

      Assuming 1 AC and 1 geyser, 4-5 kW should be good.

    • Vishal Khialani

      – All four will not run at the same time. Only 1 will run and on rare ocassions 2 might run at the same time.

      – I read the article you have given .The elders in my family can only use the shower as they can’t bend for the bucket. So I can’t use 3k instant heaters for them Hence I want to buy the 11kw.

      – My house wiring should be able to handle the load. I can run 3 ac at the same time. each is of 1.5 tones during summer nights.

      – My End Goal is to buy the most effecient heaters and ac then move to solar.

      – I am concerned of the shock which you mention. This could be the main reason I don’t go for it.

      – If not instant which is the fastest storage heater in the market ? I would love to get a toal number of min the heater was on for a day.

    • https://www.bijlibachao.com Abhishek Jain

      Hi Vishal,

      11kW water heater will significantly increase the size of Solar PV system that you would need (especially if you are planning for a grid connected net metered system). That will make it very costly. If you are thinking of Solar, then the best thing is to go for a Solar-Hybrid water heating system. A solar-hybrid water heating system is a solar water heater + electric water heater system. In that water is first heated using solar energy. If water is sufficiently heated, then electric heater will not have to do any work. If it is not sufficiently hot then the extra energy needed can be provided by an electric heater (which can be a 3 or 4.5 kW instant water heater of 3 lts). The amount of electricity needed from grid is much less in this case.

      Also Solar Thermal (technology used in solar water heaters) is 80-90% efficient in converting solar energy to useful heat. Whereas Solar PV (used in generating electricity) is just 20-22% efficient. Solar Water heaters are lot less costly (anywhere between 30-50K) whereas solar PV is extremely costly.

      If your goal is to use solar, then I would strongly recommend going for solar-electric hybrid system.

  • shawn creado

    Hi Abhishek, I am confused between an instant water heater (1ltr or 3 ltr) or a storage water heater of upto 10 ltrs. It would be for a family of 2 living in mumbai where tap water is room temperature usually. I live on the ground floor in a 6 storey building. The water usage is between 6-10 ltrs of hot water (15 ltrs warm water at most during winter) and we use a bucket. From the little research i have done i find Havells, crompton greaves and bajaj models best esp with regards to power consumption, safety features, durability and after sales services. Safety features are very important as my parents are aged and may forget to put off the power switch sometimes. I dont mind spending a little extra initially provided the cost of consumption in the long run is low. I have tried looking for 5 star ratings of BEE for such instant heater models but havent found any. Can you recommend if i should go for a instant or storage and if instant then can you suggest any models with 5 star bee ratings. Please help. Thank you in advance.

    • https://www.bijlibachao.com Abhishek Jain

      BEE star rating is not available for Instant Water Heaters. It is only there for storage water heaters. I think an instant water heater can work great if you live in Mumbai and prefer buckets. Even a 3 KW heater should also work. Havells and Bajaj are good brands. You can choose anyone of them. Instant water heater can be great energy saver for you and I would not recommend you to go for 25 lts model.

  • Krutuja Bhosale

    We live in Pune (avg temperature in winters~=20-25 C and summers-30-40 C). My husband and me are planning to buy a water heater. We are ok with bucket bath and waiting for some time (up to 10 minutes). For 2 people, which of the following ways will be with more energy saving?
    1. instant water heater (~ 3KW)
    2. immersion water heater (~1.5-2 KW)
    3. storage water heater

    • https://www.bijlibachao.com Abhishek Jain

      Hi Krutuja,

      If you are fine with waiting then instant water heater would work great for bucket bath. I think you should go for instant water heater.

  • Mager T

    I am from chennai and 4 people (2 kids) and we would go for bucket bath. The minimum temp would be 20 degrees. Considering that, Would 3 liter/4.5 KW be a better option or should i need to go for 10 liter. Also since its near by sea the salt content is high in ground water and will that have any effect on the geyser type to choose? Instant instead of storing water?

    • https://www.bijlibachao.com Abhishek Jain

      If you use bucket for bathing then a 3 lts/4.5 kW instant water heater will also work. Just go for any top brands as they all have corrosion protection.

  • Bonny

    My home town has max min of 16 degrees, and high of 45. Should I be ok with an instant water heater or do I need a 15L storage water heater for a family of 4.

    • https://www.bijlibachao.com Abhishek Jain

      We do not recommend instant water heaters for bathrooms unless you use it for bucket bath and you are fine with waiting for some time for bucket to be filled with hot water.

  • amit

    Will my MCB be operated if I use 4.5 kW instant water heater? Further max capacity my utility company giving me is 2.2 kW than they may panelize me also?

    • https://www.bijlibachao.com Abhishek Jain

      MCB will work even with 4.5 kW. MCB protects from short circuit (however while installing one you certainly need to take care of the total load it can handle). And if your electricity company is giving you 2.2 kW, then you MUST get your connected load increased.


    Hi Abhi,

    I have posted this same query on my old thread with you. but re-posting here as maybe you may not see that as it is very old Nov 15.

    I have installed a .5hp pressure pump to get the water from the overhead sintex (500lts) tank into the 3ltr Racold Instant Geyser 3kw = so that I can have a hot bath I could not install a bigger storage geyser as space was less (see pic attached fpr space)

    So now thanks to the pump – I get water in the shower – But when the geyser is on – the water gets hot for a few seconds (60seconds) and then – in a few seconds the water is cold again –
    – So you think i should have opted for 4.5kw – 3ltr?
    – I have no space on the loft for a storage geyser and the bathroom s too small to install a storage geyser inside
    – And I cannot do without the pressure pump as I am on 7th floor and the storage tank and geyser are at the same level on the loft so the water will not flow to geyser without a pump!!
    Please advise


    • ATANU DE

      May like to use Cascade Evo 11KW.

      Also you may try to increase the outlet diameter of the overhead tank by foregoing the pump

    • https://www.bijlibachao.com Abhishek Jain


      As mentioned in this article, an instant water heater is not good enough for a shower. At best you can use it for bucket bath with a slow water flow rate from the tap. But it is extremely difficult to use instant water heater for shower. Even a 4.5 kW one will not be good enough for shower. Can’t think of a better option over here if you do not have much space to put a storage one.


      Thanks Abhi.
      Its working well in slow flow for a bucket bath. Anyway if I’m saving water maybe its for the best.
      Just for my knowledge – even a 25ltr storage would not work in mycase – right? Firtly the water does not fill in the storage geyser. Then if it does due to the pump – it wont heat fast enough before the p[ump pushes it out? am i correct in these assumptions?

    • https://www.bijlibachao.com Abhishek Jain

      As long as your geyser is full of water when it is on, it should work fine. But then if you are taking water from the geyser to a loft tank, then I do not think that it will be a good solution.

      I think bucket bath would be the best as it will save energy and water :).

  • Amit Upadhyay

    Hi bijli bachao team,
    Can you advise whether invertor in any way harm led bulbs or reduce there life?

    • https://www.bijlibachao.com Abhishek Jain

      Hi Amit,

      Inverter should not cause any problems to LED bulbs.

    • Amit Upadhyay

      Thanks for responding. But I have heard from few electricians that inverted ac current from invertors break it’s circuit? Local language is LED ud jata hai?
      Please respond to this.

    • https://www.bijlibachao.com Abhishek Jain

      Inverter ACs should not have any problems working with power inverters. It can work perfectly fine.