Question

in hopes that the student would return soon, the parents kept the porch light on. the light bulb used about 75 watts. 1000 watts is a kilowatt. a killowatt hour is the amount of energy when a kilowatt of power is used for one hour. if a kilowatt hour costs 45 cents, how much does it cost to run the 75 watt light for one full week (day and night)? hint:____cents=75 watt*1 week

Answer 1

The energy consumption in kilowatt hours is the power in kilowatts multiplied by time in hours. So, for the 75 W = 0.075 kW bulb which is on for one week (one week is 24 h times 7 days = 168 hours):

0.075 kW * 168 h = 12.6 kWh

Which does cost 12.6 kWh * 0.45 $/kWh = 5.67 dollars.