Question

Determine how much it will save a year if the lights in the commercial store

and administrative offices are turned off during unoccupied periods in the

following story: "An administrative building containing 100 commercial stores

and 250 administrative offices, each containing 12 LED bulbs. Each bulb

consumes 120 W and the cost of electricity is SR 0.196/kWh,". The building works

daily throughout the year. Commercial stores and administrative offices do not

work for 4 hours a day, but the light remains on.

Answer 1

Given;

Number of commercial stores = 100

Number of administrative offices = 250

Number of LED bulbs in a single store/office = 12

Therefore;

Total number of LED bulbs = 100 X 12 + 250 X 12 = 4200

Power consumed by one bulb = 120 W

Total power consumed = 4200 X 120 W = 504000 W

1000 W = 1 kW

Therefore;

Total power consumed = 504 kW

Number of non-working hours per day = 4 hrs

Total energy consumed in those four hours per day = 504 kW X 4 hrs = 2016 kWh / day

Number of days in an year = 365 days

Total energy consumed in those fours hours in an year = 2016 X 365 = 735840 kWh

Cost of electricity = SR 0.196 / kWh

Total cost of electricity = SR 0.196 X 735840 = SR 144225

Now;

This is the amount of money which is getting wasted every year due to not turning off those bulbs.

Therefore;

Amount that can be saved every year = SR 144225