A device uses 2 W idle and 6 W active. If usage is 50% active and 50% idle, what is the average wattage?

A device uses 2 W idle and 6 W active. If usage is 50% active and 50% idle, what is the average wattage?

• A. 4.0
• B. 3.0
• C. 5.0
• D. 2.0

Answer: (A)

Power averages over time by weighting each state by how long it lasts. With half the time idle at 2 W and half the time active at 6 W, the average power is the simple average of the two: (2 W + 6 W) / 2 = 4 W. So the device’s average wattage is 4 watts.

Power averages over time by weighting each state by how long it lasts. With half the time idle at 2 W and half the time active at 6 W, the average power is the simple average of the two: (2 W + 6 W) / 2 = 4 W. So the device’s average wattage is 4 watts.