Power consumption = Power × Time
Use the formula: Energy (Wh) = Voltage (V) × Current (A) × Time (h)
If power is already known: Energy (Wh) = Power (W) × Time (h)
Convert Wh to kWh by dividing by 1000
For AC circuits, use: Power (W) = Voltage (V) × Current (A) × Power Factor
For three-phase systems, use: Power (W) = √3 × Voltage (V) × Current (A) × Power Factor
Measure voltage, current, and operating time
Multiply the values using the correct formula
Sum the energy use of all devices to get total consumption
Multiply total kWh by the electricity rate to calculate cost