If a device operates for 3 hours at a power of 1.5 kW, how much energy is used in kilowatt-hours?

If a device operates for 3 hours at a power of 1.5 kW, how much energy is used in kilowatt-hours?

• A. 1.5 kWh
• B. 4.5 kWh
• C. 9 kWh
• D. 3 kWh

Answer: (B)

Energy used equals power multiplied by time. If something runs at 1.5 kilowatts for 3 hours, the energy consumed is 1.5 × 3 = 4.5 kilowatt-hours (kWh). The kilowatt-hour is the unit that combines power and time, since 1 kW used for 1 hour equals 1 kWh. So the correct energy is 4.5 kWh. The other values would come from using different times or powers (for example, 1.5 kW for 1 hour is 1.5 kWh; 3 kW for 3 hours is 9 kWh; 1 hour at 3 kW is 3 kWh).

Energy used equals power multiplied by time. If something runs at 1.5 kilowatts for 3 hours, the energy consumed is 1.5 × 3 = 4.5 kilowatt-hours (kWh). The kilowatt-hour is the unit that combines power and time, since 1 kW used for 1 hour equals 1 kWh. So the correct energy is 4.5 kWh. The other values would come from using different times or powers (for example, 1.5 kW for 1 hour is 1.5 kWh; 3 kW for 3 hours is 9 kWh; 1 hour at 3 kW is 3 kWh).