10 kilowatt-hours is enough energy to run a 5,000-watt air conditioner for how long?

• A. 1 hour
• B. 2 hours
• C. 0.5 hours
• D. 4 hours

Answer: (B)

Energy, power, and time relate through E = P × t. The air conditioner draws 5 kilowatts, and you have 10 kilowatt-hours of energy available. So the run time is t = E / P = 10 kWh / 5 kW = 2 hours.

Two hours matches the energy provided (one hour would use 5 kWh; half an hour about 2.5 kWh; four hours about 20 kWh).