Question

Please help if you can.

Answer 1

Initially there were 10 bulbs of 60 Watt power

So total power of all bulbs = 60 * 10 = 600 W

now each bulb used for 4 hours daily

so total energy consumed daily

$E = P * t$

$E = 600 * 4 = 2400 Wh$

$E = 2.4 kWh$

now we have total power consumed in 1 year

$E = 365 * 2.4 = 876 kWh$

cost of electricity = 10 cents/ kWh

so total cost of energy for one year

$P_1 = 876 * 10 = 8760 cents = 87.60$

Now if all 60 Watt bulbs are replaced by 30 Watt bulbs

So total power of all bulbs = 30 * 10 = 300 W

now each bulb used for 4 hours daily

so total energy consumed daily

$E = P * t$

$E = 300 * 4 = 1200 Wh$

$E = 1.2 kWh$

now we have total power consumed in 1 year

$E = 365 * 1.2 = 438 kWh$

cost of electricity = 10 cents/ kWh

so total cost of energy for one year

$P_1 = 438 * 10 = 4380 cents = 43.80$

total money saved in 1 year

$Savings = 87.6 - 43.8 = 43.80$