Power factor (PF) is the ratio of real power, measured in watts, to apparent power, measured in volt-amperes. For a single-phase AC load, true PF relates average real power to RMS voltage multiplied by RMS current.
Why watts divided by volts can be incomplete
For the same real input power and RMS supply voltage, a lower PF requires more RMS current. For a single-phase load, I = P ÷ (V × PF). Use electrical input power, not LED output power or a number in the product name.
Practical example
An illustrative 600 W input load at 120 V draws 5 A if PF is 1.00, or 6.25 A if PF is 0.80. These are calculation examples, not the current ratings of a named fixture. Actual operating conditions and manufacturer data take precedence.
Power factor and efficiency
PF is different from the power supply’s conversion efficiency. It can also change with supply voltage and load level. A phase-angle-only figure does not fully describe true PF when current is distorted. Use documented input-current data or appropriate measurement for equipment planning, and account separately for startup behaviour and circuit limits.
Related terms
Apparent Power · Amperage · Voltage · Watt · Inrush Current
References
Fluke: power factor · Vertiv: power definitions and terms · MEAN WELL: power-supply operation and inrush