Define lighting power density (LPD) and how to compute energy consumption for a space.

Define lighting power density (LPD) and how to compute energy consumption for a space.

• A. LPD is watts per square meter; total lighting load = LPD × area; energy consumption = load × hours ÷ 1000.
• B. LPD is lumens per square meter; total energy = lumens × hours ÷ 1000.
• C. LPD is volts per square meter; energy = volts × hours.
• D. LPD is amps per square meter; energy = amps × hours.

Answer: (A)

LPD measures how much electrical power the lighting in a space uses per unit area, expressed as watts per square meter. To find the total lighting load, multiply the LPD by the space area in square meters, giving watts. To get energy over a period, multiply that power by the number of hours the space is used, which gives watt-hours, and then convert to kilowatt-hours by dividing by 1000. So energy = LPD × area × hours ÷ 1000. This reflects that energy is power used over time, and LPD is a density of power per area. Using lumens, volts, or amps alone wouldn’t yield energy in the same way.

LPD measures how much electrical power the lighting in a space uses per unit area, expressed as watts per square meter. To find the total lighting load, multiply the LPD by the space area in square meters, giving watts. To get energy over a period, multiply that power by the number of hours the space is used, which gives watt-hours, and then convert to kilowatt-hours by dividing by 1000. So energy = LPD × area × hours ÷ 1000. This reflects that energy is power used over time, and LPD is a density of power per area. Using lumens, volts, or amps alone wouldn’t yield energy in the same way.