Question

Suppose energy costs 0.08 per kilowatt-hour how much would it cost to keep a 40 watt porch light on all night every night for 1 month

Answer 1

(30 days) * (12 h/day) * (0.040 kW) * ($0.08/kWh) = $1.152

It costs about $1.15 to keep the light on half the time for a month.