How to calculate monthly electricity bill
A Unit of electricity is a Kilo-Watt Hour, which means you consume a Unit of Electricity when you use 1000 watts for 1 hour. Let us work out a real world example of trying to calculate the expected monthly electricity bill for a typical middle class family in India. The following table gives the wattage and daily usage time of typical household appliances owned by a middle class family in India. The total electric power consumption is calculated as follows:
|Appliance||Watts||No.||Hours||Watt x Hours||Units /day|
|TV 32 inch LED||40||1||4||160||0.16|
|Fridge 250L 4★ 501 U/year*||24||1.37|
To calculate the monthly consumption of electricity, the daily usage of 7 Kilo-watt hours has to be multiplied by 30 to get 210 Kilowatt hours or 210 units of electricity a month. If the charge for electricity is ₹4- per unit then the monthly electricity bill would be Rs.840-
How some of the items in the above table is worked out is explained like this. For the example of ceiling fans of 100 watts each. We assume daily usage of 3 fans running for 8 hours daily. So you consume 100 watts x 8 hours x 3 fans = 2400 watt-hours which is = 2.4 Kilo-watt hours, since 1000 watts makes 1 Kilowatt. So every day you consume 2.4 Units of electricity when you use the 3 fans of 100 watts each for 8 hours a day.
Similarly for 8 CFL bulbs of 15 watts each used for 4 hours daily on an average, the total current consumption of the CFL lamps will be 8x15x4=480watts and for a month the current consumption of the 8 CFL lamps will be 480/1000=0.48 KWH or units of electricity in a month.
For the fridge we have taken the annual consumption of a 4★ (4 star) rated fridge of 250 Liter capacity as 501 units in a year running 24 hours daily for 365 days in a year. This information is obtained from the Government of India's Bureau of Energy Efficiency. Dividing 501 by 365 gives us the daily power consumption of the fridge as 1.37 units a day.
In the case of an Air fryer 1500 watts is the highest power on Air fryer models. The maximum time an air fryer needs to cook a main meal is about 30 minutes. During this 30 minutes, the air fryer heater will not be 'ON' all the time, meaning that there will be intervals when the heater coil will be switched off by the automatic temperature control when the cooking temperature has reached the set cooking temperature. The heater of an air fryer consumes more than 90% of the power, the blower and other parts together consume less than 10% of the power. So it can be safely assumed that the air fryer heater coil power is 'ON' for two thirds of the time during cooking and one third of the time the power to heating coil will be 'OFF'.
Two thirds is = 0.67 and 30 minutes = 0.5 hours. So the air fryer will consume 1500x0.5x0.67 = 502.5 watt hours or approximately 0.5 Kilo-Watt Hours or half a unit of electricity per air fryer cooking cycle of 30 minutes.
An air fryer cooking time with 30 minutes is only reached on rare occasions, most of the recipes for air frying takes only about 15 minutes on an average. Thus the maximum electricity an air fryer can use is not more than half a unit of electricity in a day. In case you do 2 air frying cooking of 30 minutes each, the maximum electric power consumed by the air fryer will only be 1 unit of electricity in a day. The Air Fryer in the example given above is the one with 1500 watts power, but most of the Air Fryers have a power rating which is less than 1500 watts and therefore consume much less than the half unit of electricity in a day.
Electric power used by domestic appliances
We have provided below a table with the approximate wattage of some typical everyday used electrical appliances. Most of the electrical domestic appliances have their wattage on a label prominently fixed or stamped on the appliance. So that way you will know exactly how many watts the appliance consumes.
|TYPE OF APPLIANCE||WATTS|
|TUBE LIGHT (Electronic Choke)||36|
|TUBE LIGHT (Ordinary Choke)||52|
|CEILING FAN / TABLE FAN||40|
|CEILING FAN BIG||75|
|FRIDGE 165 LTRS||100|
|FRIDGE 310 LTRS||400|
|LED TV 40 INCH||100|
|WATER PUMP 0.5 HP||375|
|TYPE OF APPLIANCE||WATTS|
|MIXER GRINDER (BIG)||400|
|ELECTRIC OVEN 1||750|
|WASHING MACHINE TOP LOAD||250|
|WASHING MACHINE FRONT LOAD||750|
|ROOM A/C 1 TON||1400|
|ROOM A/C 1.5 TON||2100|