What Happens When the Power Factor (PF) Is Low?

I. What is “Reactive Current”?

In an ideal scenario, voltage and current are in phase. However, in reality, many power supplies generate phase lag and current distortion. Although the rated power may appear to be 100W, the actual current drawn from the grid is greater than 100W. This “excess current” does not produce light; it merely increases the load. This is the essence of low PF.

II. What problems does low PF cause?

In low-power applications, the impact is not significant. However, in large-scale lighting projects such as shopping malls, factories, and office buildings, low PF leads to increased grid load, line heating, and occupied distribution capacity.

Standards in many countries require: PF ≥ 0.9 or ≥ 0.95

This is critical to the stability of the entire system.

III. Why Do Some Lights Have Low PF?

There are typically two reasons: the driver power supply is designed simply to keep costs down.

Adding a power factor correction (PFC) circuit increases costs and design complexity. However, the benefits include cleaner current, a more stable grid, and a more professional system.

Truly mature engineering projects do not focus solely on “how many watts.” Instead, they ask: What is the PF? Does it have active PFC? Brightness is the result. PF is the attitude. How much electricity a light fixture consumes is important, but whether it is grid-friendly is even more important.