Question

A household uses the following electric appliances:
(a) Refrigerator of rating 400 W for ten hours each day.
​(b) Two electric fans of rating 80 W each for twelve hours each day.
(c) Six electric tubes of rating 18 W each for 6 hours each day.
Calculate the electricity bill of the household for the month of June if the cost per unit of electric energy is ₹ 3.00.

Answer 1

1 unit of energy equals 1 kilowatt-hour.

(a) Units spent in a day by refrigerator = 400 W $\times$ 10 h = 0.4 kW $\times$ 10 h = 4 kWh = 4 units

(b) Units spent in a day by two electric fans = (80 $\times$ 2) W $\times$ 12 h = 0.16 kW $\times$ 12 h = 1.92 kWh = 1.92 units

(c) Units spent in a day by six electric tubes = (18 $\times$ 6) W $\times$ 6 h = 0.108 kWh $\times$ 6 h = 0.648 kWh = 0.648 units

Total units spent in a day = 4 + 1.92 + 0.648 = 6.57 units

Total units spent in the month of June = 30$\times$6.57 units = 197 units

Total cost in a month = 197 $\times$ 3 = ₹ 591