Electricity Saving Tips For Homes And Offices

What are Watt, Kilowatt and a unit of electricity

By on August 27, 2015

Hindi Translation: वाट, किलोवाट और बिजली की अन्य इकाइयां (यूनिट्स) क्या होती हैं ?

When we get our electricity bills, it shows that we have used a certain number of units for the given period. When we go to buy appliances, most of them have watts mentioned on them. If you find it difficult to understand the relation between the two, then you are not alone. Electricity bill and its components are confusing to many and with this article we will try to explain what are watt, kilowatt and a unit of electricity.

Confused

Power and Energy/Electricity

Power and Energy/Electricity are two words that are used so much for each other that many feel that they mean the same. Interestingly both of them have a very different meaning. Power is the rate at which electricity is used and energy/electricity is the actual consumption. To give an analogy, power is similar to speed but electricity/energy is the actual distance travelled.

So        Power x Time = Electricity (or energy)

Just like          Speed x Time = Distance Travelled.

Power and its units

Power is always represented in watt (W) or kilowatt (kW). A thousand (1000) watts make one kilowatt. So if any appliance is rated as 1.2 kW then it means that it consumes electricity at a rate of 1200 W. Now as we discussed earlier that power is the rate at which electricity is consumed and not the actual electricity consumed, Watt or Kilowatt just represent the rate at which electricity is consumed per hour. Which means that when you buy a 100 W bulb, it does not consume 100 units of electricity but consumes at a rate of 100 W.

Energy/Electricity and its units

A unit (as mentioned on the electricity bills) is represented in kWH or Kilowatt Hour. This is the actual electricity or energy used. If you use 1000 Watts or 1 Kilowatt of power for 1 hour then you consume 1 unit or 1 Kilowatt-Hour (kWH) of electricity. So the reading on the electricity meter represents the actual electricity used. Just like the odometer on your vehicle that shows the actual distance travelled by the vehicle, electricity meter shows the amount of electricity that is used. So a 100-Watt bulb if kept on for 10 hours will consume:

100 x 10 = 1000 Watt-Hour = 1 Kilowatt-Hour (kWH) = 1 units (on your meter).

Estimating units consumed by any appliance

Now with most of the concepts explained we would like to make it easy for you to calculate how much units does any appliance consume. Most appliances have wattage written on them (either on their container box or somewhere on the appliance). Once you have the wattage, next you need to figure out how many hours a day do you use it. After that you can use the formula below:

Daily Units = (Wattage x Usage hours per day) ÷ 1000

Monthly Units = Units x 30 (or 28,29,31 based on month)

Please note that this formula may not work always. For appliances like Air Conditioner, Water Heater, Cloth Iron (any heating or cooling device) and pumps, this will not work.


Infographic3

Check this video to make it easier to understand:

Also check this video that can help you understand how many units your appliances are consuming:

Source of Information:

http://www.energysavers.gov/your_home/appliances/index.cfm/mytopic=10040

http://en.wikipedia.org/wiki/Watt#Confusion_of_watts.2C_watt-hours.2C_and_watts_per_hour


  • shyam

    Sir i use one cfl bulb and a table fan only.
    My room owner said i used 97 units in 30 days .is it possible.
    I m very tensed i paid 582 rs rate for 1 unit rs 6 rupees

    • Bijli Bachao Team

      It is not just about 1 CFL and 1 table fan. A lot also depends on how long you use them. A 23 watts CFL plus a 75 watts fan can make up to 100 watts. And 100 watts for 10 hours can make 1 unit of electricity. But still 97 looks unreal. Unless you have more things running in the room.

  • Tanuj Singh

    Dear Author,
    I want to Install a 1Kwp of Roof PV Solar System with battery and Inverter.
    How much will it cost to me…???
    How can I get subsidy and where should I approach for that.
    Hoping for your kind response.
    Thanks…!!!

    • Bijli Bachao Team

      Hi,

      You can check this video. You can get some idea: https://www.youtube.com/watch?v=2fqV3JbIEik

  • Parikshit

    You said, “For appliances like Air Conditioner, Water Heater, Cloth Iron (any heating or cooling device) and pumps, this will not work”. Please inform what formula works for these appliances. How to count units consumed by them.

  • Dr.K.Anusha

    hi,can you please tell me how much would 2 fans and a refrigerator would consume in 12hrs(overnight).i am using Haier 170litres fridge,which has 5 stars for power saving quality and written 264 units of consumption per year?
    I have noticed that its about 3units over nights,which i feel is little high..also would UPS consume more power?

  • Saptrishi Mandal

    Hello,
    This is Saptrishi Mandal need to know how to check “Earthing” in meter.

  • avik kumar

    a work need 10amp for 10hp 440v 3phase motor, for same work 20 hp 440v 3phase motor need more than 10amp?

    • Bijli Bachao Team

      Well if the work can be done by 10 HP machine then by using 20 HP you are underloading the machine. The efficiency of motor is less when it is underutilized. So assuming 10 HP machine was right sized, then yes 20 HP motor will take more than 10 Amp because it will be much less efficient for doing that job.

  • Gurmeet

    What would be the cost of using an electric oven for 1 hr if the cost of unit is ₹8?

    • Bijli Bachao Team

      Electric Oven would be about 2 KW. So 2 units in usage of 1 hour. At Rs 8 a unit it would Rs 16.

  • Manoj Sinha

    Inverter continue contacted with electric.
    Is it increase meter reading.

    • Bijli Bachao Team

      Inverters do consume electricity when kept on.

  • Sunil Thakar

    Trimming Beard at home is ECONOMICAL or one should go to salon

    • Bijli Bachao Team

      Salon is better if it is not expensive :).

    • Viral Jain

      I have Philips Trimmer using at home and Salon charges Rs. 30 for trimming beard then which one is economical ?

    • Bijli Bachao Team

      Using trimmer at home will be more economical.

  • Viral Jain

    Sir Whether iron (Non Steam) my clothes at home or should i give it to presswala Which one is Economical ???

    • Bijli Bachao Team

      Depends on how much the presswala charges you. However using iron at home in general is cheaper.

    • Viral Jain

      He Charges Rs. 4 Per Cloth and Rs. 10 per Saree then what to do ?

    • Bijli Bachao Team

      Ironing at home will be cheaper. But then one has to spend time to iron.

  • Keshav

    I am using desktop with LCD SCREEN, D-LINK WIFI ROUTER and CISCO DPC 3008 CABLE MODEM. i want to know that how much electricity (units) consumed by both modem in a month?

    • Bijli Bachao Team

      Hi Keshav,

      Typically routers consume 4-5 watts. So their unit consumption would be (5 x 24 x 31) / 1000 = 3.72 units per month.

  • Nyuwi

    Helo there,my last month meter shows 2017 kwh and this month it shows 4114 kwh so what is the unit i have consumed and how much do i have to pay if per unit is 8Rs.
    please help.
    thank you

    • Bijli Bachao Team

      Your units consumed would be 4114 – 2017 = 2097. And at Rs 8 a unit, the cost would be Rs 16776 just for the energy charges. Along with it you would get fixed charges, fuel surcharge and electricity duty/tax.

    • Nyuwi

      Wow!!!i have to pay rs 16776 just for using 2 fans?
      I don’t know whether i have given you the right kwh or not because i am not femelier with the meter.
      anyway in my digital meter this was the numbers shown last month 2017 and for this month 4117.the above numbers are the only numbers shown in the meter so i hope you are geting the picture of what im saying now..
      please help

    • Bijli Bachao Team

      If it is juts two fans then it may be that the reading would be 201.7 and 411.7. In that case your consumption is 210 units. Then at Rs 8 per unit you would get energy charges of 210×8 = Rs 1680.

      Some energy meters also measure to a single decimal place of kWh.

  • Yogesh J Ingle

    I like to know how can I increse the Pv cell efficiency using electronics components or devices?

    • Bijli Bachao Team

      Hi Yogesh,

      We are not aware of it. You will have to ask this to a PV technical expert.

  • vinay kumar

    Contact : Solar grid solutions for
    Home/ Institutes/ hospitals/ malls/ industrial areas 2 KW to 10 MW. We provide services across India at very nominal rate which are competitive in market.

    For any query, Call : 9312700996
    visit us at : http://www.solarbird.in

  • shalu

    Sir residential area m 2 kw meter kliye e unit charge kya h gzb shastrinagar m meri unit 300 to 500 k between rehti h

    • Bijli Bachao Team

      Gzb UP mein pehle 150 units ke liye Rs 4 hai, agle 150 units ke liye Rs 4.5 hai aur fir agle 200 units ke liye Rs 5 hai aur usse zyada sab ka Rs 5.5 hai. To agar aapke 500 units ek mahine ke aaye hain to aapka bill 150×4 + 150×4.5 + 200×5 = 2275 ka energy charge aayega. Uske upar 2 kW ka fixed charge aur electricity duty aur taxes aayenge.

  • gaja nand garg

    sir, there is server consuming 2540 watt , runs round the clock. How many units it will consume in a month.

    • Bijli Bachao Team

      Hi,

      2540 watts means 2.54 units in an hour. You can multiply it by 24×30 to get monthly consumption.

    • deena

      what is the rating(wattage) of server?

    • Bijli Bachao Team

      depends on the size, make, model, etc of the server.

  • Iqbal

    Dear Sir/Madam

    I am using a old desert cooler, it’s Motor (fan) was rebind from local mechanic, it consume 0.7 unit (3688.5 – 3687.8) in the 3 hours (morning) , I have digital meter (Electricity Board Chandigarh), What actual Wattage consumption is for this motor? (Pl calculate for 10 hr too)

    Thanking you

    • Bijli Bachao Team

      0.7 units in 3 hours means 0.7 kWH in 3 hours or 700 Watt-hour in 3 hours. So its wattage would be 700/3 = 233 Watts. And if it consumed 0.7 units in 3 hours then it would consume (0.7/3)*10 = 2.33 units.

  • Limras

    I want to know that 1.2 ton ac with 5star rating.. How many unit it will takes in 8 hours..

    • Bijli Bachao Team

      Hi Limras,
      How many units an AC consumes per hour depends on lot of factors, like the size of the room, os the Ac oversized or undersized, placement of AC, and brand etc.. So we cannot accurately calculate how much an AC will consume. But a BEE 5star 1.2 ton AC should consume about 0.9-1 units/hour. So for 8 hours it should consume about 7.2-8 units.

  • SHANAWAZ SHAIK

    I to know one thing. power plants produce some power. assuming that a plant produce 1MW power. that means is it for a day or a month or an year. from 1MW how many units will we get. I heard that we can produce 1MW solar power from 1 meter square place. Is it true. hear we have heat about 38 – 41 degrees centigrade.

    • Bijli Bachao Team

      Hi Shanawaz,

      1 MW is 1000 KW which is the rate at which electricity is produced by power plant. It is not the actual electricity units produced. If 1 MW plant runs continuously for 1 hour it will produce 1 MWH = 1000 KWH = 1000 units of electricity. You can read more about a solar power plant vs regular power plant on this link: https://www.bijlibachao.com/energy-efficiency-and-other-articles/comparison-of-the-output-capacity-of-a-coal-power-plant-vs-solar-power-plant.html

  • VIVEK

    HI SIR I HAVE DOUBT FROM BE UNITS..I WANT WHICH READING DAILY I TAKE AND HOW TO CONVERT TO UNITS

    • Bijli Bachao Team

      Hi Vivek,

      I could not understand your question.

  • pradeep

    I want to know that 1.5 ton ac with 3star rating
    how many units it will consume in one hour

    • Bijli Bachao Team

      Hi Pradeep,
      The electricity consumed by an AC depends on lot of factors. So we cannot accurately calculate how much an AC consume in an hour. Bua A 1.5 ton 3 star AC should consume approximately about 1.4 units/hours.

  • Raj

    if one water pump- 1 inches pipes, of 1 Hp runs 5 hours a day then how much units it will consume in a day or in a month………

    • Bijli Bachao Team

      Hi Raj,

      1 HP is 750 watts. And 750 watts for 5 hours is 750×5=3750 Watt hour or 3.75 kWH or 3.75 units of electricity in a day. Assuming 30 days in a month it is 112.5 units a month. This is a rough calculation as the consumption will also depend on load (full load, partial load, etc).

    • raj

      thanks for answer….its good to manage electricity bill for me ……

    • aruna

      1 HP is 750 watts. And 750 watts for 5 hours is 750×5=3750 Watt hour or 3.75 kWH or 3.75 units of electricity in a day. Assuming 30 days in a month it is 112.5 units a month. This is a rough calculation as the consumption will also depend on load (full load, partial load, etc).- iF IT IS DIGITAL METER MEANS WHAT IS THE CALCUALTION

    • Bijli Bachao Team

      Calculation will remain the same even with digital meter.

  • Vinay kumar

    Contact for Solar grid solutions for Institutes, hospitals, malls, industrial areas and large scale plant 200 kva to 10 MW. Our manufacturers have very vaast experience in this field. We provide services across India at very nominal rate which are competitive in market.

    For any query, please feel free to contact us at +91-9312700996

    • Jarnail Singh

      Hello sir I want to put one me solar plant in Punjab ,mukerian tehsil I have 4 acre land .how much it cost and how much land I need for 1 mw unit

    • vinay kumar

      Dear Sir Thanking you …
      if you have to plan setup the 1 MW pv solar power plant Land requirement is Minimum 5 acres land (non Agriculture conversion land )

    • Bijli Bachao Team

      You need about 4.5 to 5 acres of land to setup 1 MW plant. You can refer to this link to get more information: http://efficientcarbon.com/services/energy/renewable-energy-advisory/frequently-asked-questions

  • arsh aftab

    sir ,
    mere 1.5 ton split ac hai. jo ki 1900 watt ka hai . mujhe 8-10 hour chalana hai .mere month me kitne unit kharch hoga.

    • Bijli Bachao Team

      Hi Arsh,
      Aapka 1.5 ton AC lagbag ghante ka 1.5 units consume karega, toh 10gante ka usage ke liye lagabg 15units consume karega. Aur agar aap 30 din use karoge to mahine ka karib 450units consume karega.

    • Rohit Saxena

      A 1.5Ton A/C if its not five star would consume near to 2KW & Arsh is correct in specifying 1.9KW. Hence the calculation would be 19Units per day & for a month it would be 19X30=570 Units.
      tks

    • Bijli Bachao Team

      Hi Rohit,

      It would consume 1.9 kW only when the compressor is running. But the compressor does not work all the time. Compressor running time depends on multiple things that drive the heat load. So it truly depends, but will not always be 1.9 units per hour.

    • saurabh

      12 units

  • Paramjit

    Dear Sir,
    A Machine run at the power of, 8.2kw / 380v / 50Hz,

    Can you please help me to know how much units of electricity it will consume in one hour?

    • Bijli Bachao Team

      It is 8.2 kW so it will consume 8.2 units in 1 hour.

    • Paramjit

      Thank You.

  • remya

    i forgot to switch off iron box(without using) for 14 hr dos my electricity bill will increase very high

    • Bijli Bachao Team

      Hi Remya,
      Yes the iron box would have consumed a lot of electricity as it turns hot and cold for 1 4hrs. So it would have consumed roughly about 5-6 units.

    • remya

      thank you sir

  • Digambar S Phule

    my office use 1200 units electricity per month so i want know how many kilowatt we use per month

    • Bijli Bachao Team

      1200 units is equal to 1200 kilowatt-hour. So you have used 1200 kwh per month.

      Kilo watt is just the rate at which you can consume electricity (just like speed). Kilowatt hr or unit is the actual electricity consumed.

      Your question is like asking: I have traveled 1200 km in a day … I want to know what was my speed during the day. ….. so if for this question your answer is 1200/24 = 50 Km/hr ….. then for your question the 1200 kWh / (30*24) = 1.677 kW. …. but that is average speed and at any moment the speed may vary.

  • Nisarg J

    Dear Sir, I have a single phase connection at my appartment and my alloted load is 3kw in gandhinagar kudasan. Our electricity provider is ugvcl. Now I want to install 3split ac and 3 water heaters. My question is do I need to change the entire wiring of my house? What is the procedure to increase my load to 10kw with ugvcl? How much do I have to spend for this entire procedure.?

    • Bijli Bachao Team

      Hello Nisarg,

      You certainly need to upgrade the load to 10 KW. Your wiring should be such that it can handle high current. You may contact your electrician to check the same. As for the procedure, you may contact UGVCL customer support for the same.

  • Raj

    Will u tell me which ac consume more electricity window one or split one……if both of them having same rating and both of them are use same no. Of hours in a day…

    • Bijli Bachao Team

      Hi Raj,
      The BEE star rating of window AC is one level lower than that of split AC. So window AC will consume more electricity.

  • hir

    Hi Abhishek, those articles are very helpfull, for a common person to understand the daily usage of their home appliances …

    thanks for sharing… :)

    • Abhishek Jain

      Hi,

      I am glad that you found the information useful :).

    • sri

      thanks to solve my doubt

    • Kamlesh Gadaria

      Hi Abhishek,

      This Information is Very Helpfull for Buying Any Home/Office Application.
      Thanks…

    • Bijli Bachao Team

      Thanks. We are glad that you found the information useful.

  • Shubham Singh

    Correction in the line “Watt or Kilowatt just represent the rate at which electricity is consumed per hour”, it is actually per second not hour. 100 Watt means 100 Joule per second energy… by the way nice article, keep on posting.

  • MANI

    5 KW OF POWER IS HOW MANY UNITS

    • Shubham Singh

      1 Unit = 1 Kilo Watt hour(kwh) = 1000×3600 Joule per sec
      5KW = 5000 J/s = 5000/3600000 Unit = 0.0014 unit
      it means that if you use 5 KW of power for 1 second then it will consume 0.0014 unit
      i hope you got it…

    • Abhishek Jain

      5KW is rate of unit consumption. If you use 5KW for 1 hour it will be 5 units.

  • Ravi

    Hi how to find the electricity meter number and unit consumption in a digital meter.?

    • Abhishek Jain

      Hi,

      Meter Number will differ from make to make. For unit consumption you will need previous months reading and current reading.

  • csk

    Good Article :)

  • pradeep

    Sir begging you to give the clarification on TO PRODUCE 1MW OF CURRENT HOW MUCH COAL IS REQUIRED. Because i would like to give paper presentation on current conservation

    • Abhishek Jain

      Hi Pradeep,

      I seriously do not have any idea on the same.

  • pradeep

    Sir to produce 1megawatt of current howmany tons of coal is required?

  • aamir

    aamir Islamabad
    it is very informative, thnx

    • Abhishek Jain

      I am glad that you found the website useful.

  • Malu

    Hi
    I am a student staying at a PG in Delhi and have separate electronic metre installed for my room. A ceiling fan and tubelight are the only electronic gadgets i use in my room. In my previous PG i used to keep both the tube light and ceiling fan switched on for longer time since the room was dark and dingy.The ceiling fan was used almost for the whole day excepting 3-4hrs depending on my class timings. Whereas the tubelight would be in use for nearly 12hours a day. Then electricity consumption came around 44 units per month.
    However, now i shifted to a new PG. Here i do not use tubelight for more than 6-7hrs a day as the room has good ventillation and is not dark.The usage of ceiling fan is same as that of my previous PG. However, I found that if I a spent an entire day in my room with the ceiling fan running and tubelight switched on for 6-7hrs, the electiricty consumption is 3-4 units per day. I believe this is abnormal as by the end of the month i’ll have to end up paying for nearly 90units of electicity(for a ceiling fan and tubelight), that too after my electricity consumption having gone down from that of my old PG. I have asked the land lady to get the metre checked, but she is saying that its normal and she will bring her electrician to check the metre. Kindly advice on what is to be done.
    Malu

    • Abhishek Jain

      Hi Malu,

      A regular ceiling fan consumes about 75-90 watts depending on the efficiency of the fan. Assuming that it is most inefficient 90 watt fan. Then in 20 hours it would consume (90*20)/1000 = 1.8 units a day or 54 units in a month. If we assume that it is 75 watts fan then it would consume 1.5 units a day or 45 units a month.

      So from the fan itself the power consumption is more than 44 units. I think your old place had electromagnetic meters which tend to slow down with time (and that is the reason why DISCOMs shifted to electronic meters).

      Now coming to tubelight. Again I assume that you have regular T8 tublight which is about 45-50 watts (it may be a bit more than that as well). Assuming 50 watts in 12 hours it would consume (50*12)/1000 = 0.6 units, so in a month that will be 18 units. In 7 hours it would consume (50*7)/1000 = 0.35 units, so 10.5 units a month.

      So ideally your old bill should have been about 50 + 18 = 68 units. And your new bill should be about 50 + 10.5 = 60.5 units.

      Now you have only considered fan and tubelight. Please make sure that you are not using any laptops, refrigerators, any other appliance that works on electricity. If you do not have any other appliance then 90 units is on higher side.

      Also if you use your fan for 24 hours then it would consume about (90*24)/1000 = 2.16 units a day or about 65 units a month. If the fan is really old and not maintained well then it might also go up to usage of 100 watts.

      You can certainly get your meter checked, but ask the electrician to check wattage of each appliance.

  • krishan

    unit 111 convert into killowatt

    • Abhishek Jain

      1 unit is 1 kWh. So 111 units will be 111 kWh.

  • online king

    thank you vermuch also please update home appliances and their capacity

  • SATISH KUMAR VIJ

    Dear Abhi,

    The make is Haier(2013) & Voltas(2014).

    Place is Ambala

    thanks.

    • Abhishek Jain

      Hello Mr Vij,

      A BEE 2 star rated 1 ton AC would be rated to consume 1150-1200 watts power. The AC is rightly sized only if the room does not get direct sunlight on the roof/walls. Else you need about 1.3 tons of cooling. Assuming it is rightly sized, then an AC rated at 1150 watts would be on for about 70% time in peak summer (when outdoor temperature is about 48 and you keep thermostat temp at 28), then power consumption in an hour would be (1150/1000)x0.7 = 0.8 units. If the AC is undersized it might increase to 0.9 or 1 unit per hour. If it is highly undersized (which should not be the case if your room is 11×10), then the total can go up to 1.15 units per hour (assuming it is 100% on). Also it may consume more than that as well in case the outdoor unit is directly facing the sun. Because 1150 watts is power consumption in ideal situation. If the outdoor unit faces sun, then condenser efficiency goes down and it starts taking more current. 7 units in 6 hours means that the compressor is not stopping or the temperature setting on thermostat is not getting attained in the room. I hope you keep the rooms tightly closed (doors as well as windows) when you switch on the AC.

  • SATISH KUMAR VIJ

    I HAVE 2 ACS OF ONE TON 2 STAR EACH. I HAVE SET THE TEMP AT 28 DEGREES WITH FAN ON. THE ACS ARE RUN FOR 6 HRS DAILY IN THE NIGHT. THE ROOM SIZE IS 11X10. I HAVE NOTICED THAT THE UNIT CONSUMPTION IS VERY HIGH AFTER NEW METER HAS BEEN INSTALLED. I HAVE CALCULATED THE UNITS OF AC CONSUMPTION TO BE 14. IS IT RIGHT? BECAUSE WITHOUT AC MY CONSUMPTION WAS 8 UNITS & NOW IT IS 24 UNITS ON AVERAGE

    • Abhishek Jain

      Hello Mr Vij,

      What is the brand/model that you have purchased? 7 units in 6 hours certainly looks on a higher side at temperature of 28 degrees. Are these new ACs or old ACs?

    • SATISH KUMAR VIJ

      Dear Abhi,

      The make is Hier(2013) & Voltas(2014.
      Place is Ambala
      thanks.

  • Raj

    Hi Abhishek ,

    I want to how much electricity is required to pump xxx (eg: 100 gallons) of water to the 2nd floor water tank from ground floor?

    I just want to know units consumed….!!

    Thanks,

    Rj

    • Abhishek Jain

      Hi Raj,

      Essentially by moving water two floors we are changing the potential energy of water. The change in potential energy is

      mass x gravity x height

      100 gallons is almost 378.54 kg
      gravity is 9.8 m/s2
      height let’s assume is 25 ft or 7.63 mts

      so energy is 378.54 x 9.8 x 7.63 = 28267.85 joules = 0.008 kWH.

      Now assuming efficiency of pump is just 45% then pump would consume 0.018 units of electricity.

  • Ganesh

    Please clear my confusion

    What is Ah w.r.t domestic electricity ?
    When somebody tells that we have electricity with Ah what does it mean?
    do Ah allows run more equipment with more watt usage?
    what is the maximum watt can be consumed by any equipment without Ah(without any additional transformer or stabilizer for ex immersion coil also I know that watt consumption is depend on item which we purchase but I am speaking about maximum watt item which we can run without ah, I need that maximum watt) for domestic electricity in india?
    How volts affects the watts?
    also finally whats the maximum watt can be consumed by any equipment with Ah

    Kindly don’t give explanation with formulas I am weak in mathematics :)

    • Abhishek Jain

      Ah is typically used for batteries and represents the amount of energy it can store. Every battery has certain voltage and VAh is a unit for energy (A 12 V battery of 150 Ah size can store 12×150 VAh energy). Watts is rate at which the energy is used. Now not all of the VAh can be used and thus useful energy (Wh) is roughly 0.8 of the total VAh value. So Wh (or watt hour) the above battery stores = 12x150x0.8 = 1440 (approx). And so if you have a 10 watt bulb you can run it for 1440/10 = 144 hours.

      Sorry I could not explain it to you without formulas.

  • surinder bansal

    i have i ton o genral ac how many unit per hours.

    • Abhishek Jain

      which model? What is the star rating?

  • Shalini

    Hi i have one 1.5 ton 5 star ac 1480 watt.
    I run it at 25-30 c° 90% of the time and 10% of the time it runs at 16c° for an average of 10 hours a day(6 days in a week in day time) and 1day 15 hours throughout the day.
    What’s going to be the monthly unit and the electricity bill.? We pay rs8 per unit.
    Also tell me how to read the meter.
    Suppose it shows 21 so is it 21 unit or 2.1 unit?

    Need your help asap. Thank you in Advance bro.

    • Abhishek Jain

      Hi Shalini,

      If the AC is rightly sized (not undersized or oversized), it should consume about 1 to 1.1 unit in an hour when you run it at 25 to 30. At 16 it will go up to 1.3 or 1.4 units an hour (both assuming temperature outside is not more than 35-36).

      Meter always shows the absolute number and there are no decimal places in units. And when calculation happens it is previous reading minus current reading in units.

  • Rusi

    How to calculate the total electricity load of a typical flat .
    How to figure out whether the meter required would be 3 phase or Single phase.

    • Abhishek Jain

      Hi,

      If you can provide a list of appliances that you have, we can help you calculate the load. To choose between single and 3 phase, you can read this: https://www.bijlibachao.com/electricity-bill/what-are-single-phase-and-three-phase-connections-and-how-to-choose-between-the-two.html

  • surya

    good article. SIr, a 1.5 ton AC would require approximately 5KW power,isnt it? If Iam correct then how many units does it consume for 1-hour.If im wrong,please help me in converting ton to KW

    • Abhishek Jain

      Hi Surya,

      Typically 1.5 ton ACs require 1.4-2 kW of power depending on BEE star rating. 5KW is a lot. Although there are several factors on which electricity consumption depends as listed on this page: https://www.bijlibachao.com/air-conditioners/things-that-impact-electricity-consumption-in-air-conditioners.html …. but to do a very high level calculation we assume that AC compressor is on for 70% time. So in 1 hour a 2 kW AC would consume 2 * 0.7 = 1.4 units of electricity (typically at temperature of 22 on thermostat and outside temperature of 34).

      Also ton is not directly proportional to power consumption. It is proportional to cooling capacity kW.

    • pratibha

      how much kilowatt meter should be connect to1 ton a.c or for 1.5 ton a.c 3 star for home.(single a.c)

    • Abhishek Jain

      You should consider about 1.5 kW for 1 ton BEE 3 star AC and 2 ton for BEE 3 star 1.5 ton AC.

    • Gurpreet

      hello there ,i brought onida AC in 2007 jispe likha hai 4500Kcal/h ..
      bhaut bijli khaata hai ,, kyaa kru ???
      Ac bhi lagwaaya aur chlaa bhiu nahi sakte :-\

    • Abhishek Jain

      sir aap 25-26 par AC chalao, saath mein pankha chalao. Aur yeah bhi dekho ki room band hai aur bahar ki hawa andar nahin aa rahi hai. Try applying some insulation techniques that we have mentioned on this link: https://www.bijlibachao.com/save-electricity/insulation …. garmi ka ghar mein aana kam kar do AC ka bill waise hi kam ho jayega :)

  • Deepak

    You have written…

    “For appliances like Air Conditioner, Water Heater, … , this (formula) will not work.”

    Why ? Is it because, e.g. for Window AC’s if the specs says 1130 Watts, does it means with the compressor running ? So actual units consumed may be less as the AC is cut-off on reaching the desired temprature?

    Even then, your formula should atleast give approximation ? Atleast it can be helpful while comparing between two products?

    • Abhishek Jain

      That is right. In ACs, Water Heaters and Electric Iron there is a thermostat that switches off the appliance when the appropriate temperature is reached. In ACs, the compressor goes on and off and the peak watts mentioned on the specs is when the compressor is on. The units consumed in AC depend on several factors as mentioned in this post: https://www.bijlibachao.com/air-conditioners/things-that-impact-electricity-consumption-in-air-conditioners.html

      As an assumption while doing payback calculation we take actual unit consumption to be 0.7 x (AC watts). So 1130 x 0.7. But that is very high level approximation. Temperature setting on thermostat plays a very important role. In some tests that we have done on our own AC, we observed that a 1.5 ton window AC which is rated at 1990 watts consumed:

      1.4 units at 22 degrees without ceiling fan which is about 0.7 times 1990
      1 unit at 26 degrees with ceiling fan on (giving same comfort as AC at 22 degrees)
      0.8 unit at 26 degrees without ceiling fan.

      If you keep it at 18 degrees it will be more than 0.7 times the power. Also it will depend on the size of the room. If you put a 1.5 ton AC in small room, it will cut off quickly and will also consume more electricity. If you put 1.5 ton AC in a huge room, it will run the compressor continuously. So an approximation itself will be highly approximate :).

  • Vinod

    Great help…. Thanksss

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