### How to calculate monthly electricity bill?_Electrical Power or energy calculation

The unit of energy measurement shown on an energy meter is Kilowatt-hour(kWh).
Therefore, When we say 1 unit, it is 1kWh.
(i.e.,) 1 unit = 1kWh.

Now, to calculate the energy consumed in joules for using an equipment rated at W (say, 40W) for a period of T (say, 1Hr).

We have,
1 watt = 1 joules/second = 60 joules/minute = 3600 joules/hour
Similarly,
1 kilo-watt =  3600*1000 joules/hour = 3.6MJ/h

Therefore, 40W = 40 joules/second

If a 40W light is lit for 1 hour,
Energy = 40 * 1 = 40Wh
For this 40W light to consume 1 unit of power, it should be lit for t = 1000/40 = 25 Hrs.

Approximate power rating for various domestic equipments are listed below. (Ratings may vary)

 Appliances/Device Approximate Load (Watts) Lamps (Bulb) 60 Lamps (CFL) 15 Tube Lights 40 Electric iron 750 Immersion heater 1000 Water heater/Geyser 2000 Instant Geyser 3000 Refrigerator (165 liters ) 150 Window air -conditioner ( 1.5 ton) 2650 Room cooler ( medium) 200 Table fan/ceiling fan 75 Exhaust fan 150 Washing machine 400 Television 100 Mixer 500 Wet Grinder 300 Microwave oven 1200 Computer 200 Mosqutio Repeller 9 Pump motor (1 HP) 740 Battery Charger 7

Similarly you can calculate the energy consumption for home appliances individually for a day and the sum will give energy consumption for a day and multiplied with 30 gives your monthly consumption. Multiplying with 60 gives you bi-monthly consumption.
You can calculate monthly consumption here.

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