How to Calculate the Electrical load of your house?

Be it for deciding the roof top solar plant capacity or for checking the excess electricity consumption of your home or office, we need to know the total electricity load we are consuming. Calculating the total electricity consumption of a building is not that hard.

The electrical load of a building is the total electrical load consumed by all the electrical appliances used in the building like the tube lights, fans, ACs, Refrigerators, computers etc.

So, to calculate the electrical load of the house, all we have to do is, list all the electrical appliances, used in our home of office, find the electricity consumed by that appliance and finally add them.

Note: This is an approximate method to calculate the electrical energy load of a building.

This method is suitable to calculate the electrical load or electrical energy requirement of a residential home, electrical load of an office building, electrical load of a factory, or any other building or space.

But first, what  do we really need to calculate!

Before moving further with our calculation, lets understand what we are actually interested in. We know our electricity is measured in terms of Killo-watt hours. This is what we are billed for. Killo-watt-hour is the unit of electrical energy.

All the electrical appliances come with a label showing their electrical properties like, voltage, Current rating or the Amps value, frequency and other parameters. Voltage and current are the properties we will take into consideration here. Why? Because, to calculate the total electrical energy consumed by the appliances we need to calculate the watt or power consumed by that appliance.

Sometimes the appliances mention the wattage of that item. This makes our life easy. All we have to do is multiply the wattage with the total time(in hours) for which it is used.

Now, Power or Wattage = Current x Voltage

and, Electrical Energy = Power x Total time the appliance is running (in hours )

Lets move to the calculation part

To calculate the electrical energy consumption of your house, follow the steps below :-

  1. List all the appliances or items that run on electrical supply on a paper.
  2. Count the quantity of each item
  3. Check every appliances label for its electrical properties. If the label is damaged, the search for the item on the internet and you will get its electrical properties.
  4. Write the current and voltage of these items. For United states, the voltage for residential homes is 120V, whereas for most of the other countries its 240V.
  5. Finally write down the approximate no. of hour you use the appliance in a day
  6. For each item, multiply the Amps with Voltage  and then with the no. of hrs. This will give you the energy consumed by the that appliance in watt-hour.
  7. Or, if you have the wattage of the appliance, just multiply it with the total time (in hours)
  8. Devide the watt-hour by 1000 to get the Killo-watt-hour.
  9. Multiply the Killo-watt-hour of an appliance by the total quantity of that type of appliance.
  10. Add  the Killo-watt-hour values of  all the electrical appliances.
  11. Now to the total value multiply a factor of 0.6
  12. The final value will give you the total electrical energy consumed by your house in a single day.

Note : you don’t have to worry about the voltage of the item. In US its 120 Volt and in India and most of the other countries its 240 Volt for domestic purpose.

Let us take an example.

Consider an average home with the following electrical appliances

Sl No.  Electrical Appliances Quantity Wattage Hours Killo-watt-Hour/ KWH
1. 20 Watt Tube light 5 20 8  160
2. 10 Watt bulb 3 10 8  800
3. Ceiling Fan 4 60 8  240
4. Exhaust Fan 1 100 2  200
5. TV 32″ LED 1 55  6  330
6. PC/ Laptop 15.5″ LCD monitor 1 40*  2  80
7. Washing Machine 1  700  1  700
8. Refrigerator 230 Ltr 1  40  24  96
9. 1.5 Ton Air Conditioner 1  1200  2  2400
10. Mixture/Grinder/Juicer 1  1000  0.5  500


Find the electrical power consumption by home appliances

Now as we know the electrical load of this building will be the total electricity consumed by the above appliances, so the first thing for is to know the electricity consumed by these individual appliances

So the total energy consumed by all the appliances in a day is = 5506 x 0.6 = 3303.6 Wh = 3.3 KWH

So in the above example the total energy consumed by the house is 3.3 KWH or 3.3 units.

** The above example is an approximate calculation.

By knowing the correct energy consumption of your house, you can take measures to lower your electric bill. Also if you are planning to install a rooftop solar system, calculating the energy consumed will help you deciding the capacity of the solar plant.

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19 Responses

  1. swapan ranjan guha says:

    Dear Sir
    Please notify me through my email, electrical load calculations of lighting, receptacles, in commercial buildings, dwellings, industrial premises etc.

    • Ashish says:

      The process of calculating the electrical load of industrial buildings, is as that of calculating the electrical load of a home. You need to count the number of total light fixtures and multiply them with the wattage of the light fitting
      and calculate the no. of receptacles and multiply it with the wattage of the receptacle and then add both.
      If you still need clarification then you can ask me or send the total details and i will calculate it for you.

      • Olufunmilayo kayode says:

        I will like to know how to get the total load of a building.
        I have some designs that am working on and I need to know the total load of each building to know the size of transformer to be used.

  2. Glenda Haass says:

    Say, you got a nice blog post.Thanks Again.

  3. Jan says:

    This is good. Calculation method. I will request to build a calculator so that if any one in need has just put the data.

  4. Thanks for sharing useful information with us. It really is helpful to me. I always like to read quality material. Thanks for sharing with us.

  5. Gizat says:

    I want to know about building instalation

  6. kirubel says:

    Dear Sir
    Please notify me through my email, electrical load calculations of lighting, socket receptacles, in commercial buildings, dwellings, industrial premises etc.

  7. rohit says:

    Is this calculation same for 3 phase supply? also if water pump motor is of 2.2 KW / 3 HP will it consume 2.2 Units in one Hour ? Thanks,

  8. Dawudu Ibrahim Shanzhi says:

    Thank you for this very helpful article. It has really been helpful. Please, I am working on some building plans….. I have some pictures for the type of building in the estate … I will like to know in detail what the power requirement will be like. And if you have something like a programmed spread sheet/calculator for an exercise like the one above I will be very grateful to have it.
    Hopefully, we can even work together going forward.

  9. Kamran Ali says:

    I think sir the ceiling fan and refrigerator calculation is wrong. If i m wrong please correct me.
    Thnx so much for such a wonderful blog.

    • Moeez Anwar says:

      What is meant by factor 0.6…??

      • Ashish says:

        It is the diversity factor. Taken as 60%. the maximum demands of all the loads connected to a source usually do not happen simultaneously. Instead, maximum loading demands of various loads occur at different period of times in a day. Because of this typicality of electrical load, we can construct a comparatively smaller source of electricity to fulfil a significant number of consumers or loads. Here the term diversity factor comes into the picture.

  10. Sowunmi Nofiu Adebola says:

    I must appreciate you for this USEFUL piece, thanks a million.
    Meanwhile, I have a little observation here, the quantities of the electrical appliances was not factored into the Total Energy Consumed.
    Any special reason(s) for this?

  11. Jay says:


    It is 5506*.6 not 5506*.8

  12. Eddy says:

    How can I calculate the load of a four bedroom flat, to know the size of the cable which i can use

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