Electric Energy Consumption

 Electric Energy Consumption is calculated from electric meter installed by electricity authority at our

home. This meter measures electric energy in kilowatt hour. For our convenience 1 Kilowatt hour is said to be 1 Unit. The cost of 1 Unit electricity is same all over the country and differs from country to country. Thus to calculate energy consumption we need following data.

Electric power in kilowatt, time in hour and to calculate amount to pay we need rate per unit of electricity.

Q. If a heater of 1,200 watts is used daily for 30 minutes what is monthly power consumption? How much will be electricity bill if per unit we have to pay Rs.12?

Here, Power(P) = 1,200 watts = 1,200/1,000Kw = 1.2 Kw

Time of consumption per day = 30/60 = 0.5 hours

Total Time of consumption(T) = 0.2 x 30 =15 hours

So, energy consumption = P x T = 1.2 x 15 = 18 units

Amount to pay = consumption x rate  = 18 x 12 = Rs.216.

Q. At a home there are 5 bulb of 60W used daily for five hours and one iron of 1,000W used daily for an hour. What monthly bill should be paid with the rate of Rs. 10 per unit?

Here, for bulbs,

 P = 5 x 60 = 300W =300/1000 = 0.3 Kw

T = 5 x 30 =150 hrs(Monthly)

Consumption = P x T = 0.3 x 150 = 45 units

For Iron, P = 1,000W = 1Kw

T = 1hr x 30 = 30 hrs(Monthly)

Consumption = P x T = 1 x 30 = 30 units

Total consumption = 45 + 30 = 75

Rate = Rs. 10 per unit

So, total bill = consumption x rate = 75 x 10 = Rs. 750