Demand (kW) is defined as which of the following?

Demand (kW) is defined as which of the following?

• A. The average power over a period
• B. The maximum power used during a period
• C. The total energy used over a period
• D. The time-average of energy use

Answer: (B)

Demand in kilowatts reflects the peak, or maximum, power draw during a defined interval. It records the highest instantaneous power the building requests from the electrical supply within that period, not the average or the total energy consumed. Utilities use this peak to determine demand charges because it shows the capacity the grid must be able to handle at once. For example, if a building runs at 120 kW for 15 minutes and 40 kW for the remaining 45 minutes of an hour, the demand is 120 kW. The total energy used would be measured in kilowatt-hours (kWh), and the time-average of energy use would be that total energy divided by the period, which is typically lower than the peak. So the peak power during the interval best defines demand.

Demand in kilowatts reflects the peak, or maximum, power draw during a defined interval. It records the highest instantaneous power the building requests from the electrical supply within that period, not the average or the total energy consumed. Utilities use this peak to determine demand charges because it shows the capacity the grid must be able to handle at once. For example, if a building runs at 120 kW for 15 minutes and 40 kW for the remaining 45 minutes of an hour, the demand is 120 kW. The total energy used would be measured in kilowatt-hours (kWh), and the time-average of energy use would be that total energy divided by the period, which is typically lower than the peak. So the peak power during the interval best defines demand.