Useful Formulas - Electrical Formulas

Demand for Power (kW)
= System Input Wattage (W) ÷ 1,000

Energy Consumption (kWh)
= System Input Wattage (kW) x Hours of Operation/Year

Hours of Operation/Year
= Operating Hours/Day x Operating Days/Week x Operating Weeks/Year

Lighting System Efficacy (Lumens per Watt or LPW)
= System Lumen Output ÷ Input Wattage

Unit Power Density (W/sq.ft.)
= Total System Input Wattage (W) ÷ Total Area (Square Feet)

Watts (W)
= Volts (V) x Current in Amperes (A) x Power Factor (PF)

Voltage (V)
= Current in Amperes (A) x Impedance (Ohms) [this is called Ohm's Law]