What power factor is
Power factor is the ratio of real power that does useful work to the apparent power drawn from the supply, expressed from 0 to 1. A power factor of 1 means all the drawn power is used; a lower figure means part of the current is not doing useful work.
For an LED display the loads are the power supplies and the drivers, which are switched-mode and can draw current in a way that lowers the power factor if not corrected.
Why it matters for the supply
A low power factor means the supply must deliver more current to do the same work, so cables, breakers and transformers are sized larger than the real power alone would suggest.
On a large wall this raises the cost of the electrical build and can breach the limits a building or a local grid imposes on reactive load.
Correction in the display
Active power-factor correction in the power supplies raises the figure close to 1, so the wall draws close to the real power it consumes. This is a property of the supply design, not an add-on.
The corrected figure should be confirmed on the delivered power supplies, because the value printed on a brochure depends on the actual supply model used in the cabinets.
Where it is specified
Power factor is stated alongside the rated power and the inrush current, because all three describe how the wall loads the electrical system at start-up and during operation.
For a permanent installation the building's electrical engineer uses the figure to size the feed, so it is part of the power planning, not a footnote.
Common mistakes
The frequent error is planning the supply from real power only and ignoring power factor, which leaves breakers and cables undersized for the actual current.
Another is assuming all LED supplies correct to the same level, when cheaper supplies can sit well below 1 and load the site more than expected.
What to write into the specification
State the power factor of the supplied power units and the rated and inrush power, so the electrical build is sized to the real current, not the real power alone.
Name the power supply model and its correction level, and tie the figure to the site limit, so the wall passes the building's reactive-load requirement on connection.
Checking power factor on a quote
Ask for the power factor of the actual supply units quoted, not a generic figure, because the value follows the supply model fitted to the cabinets.
Confirm the electrical build is sized from the real current including power factor, so breakers and cables are adequate when the wall runs at full brightness.
Power factor and the utility limit
Some sites cap the reactive load they will accept, so a low power factor can block connection or trigger a penalty even when the real power is within the feed. The supplier confirms the figure against the local limit before the wall is commissioned, because correcting it after install means swapping power supplies across the wall.
The figure also changes with how the wall is run. A wall held at full brightness with aggressive cooling draws a different current shape than the same wall at 40 percent for a shop window, so the power factor is stated for the expected duty and re-checked if the duty changes, keeping the electrical build valid as the use evolves.
Two quotes, different supply load
Two walls drew the same active power, but one had poor power factor and pulled more current from the supply. The building's feeder had to be upsized for the uncorrected unit.
Inrush ignored, breaker tripped
A site sized only to running watts saw the breaker trip at startup because inrush and power factor were not stated. Specifying both up front sized the protection correctly.
How to apply this
- State the power factor in the spec Require active power-factor correction and a stated figure in the quotation so supplies are compared on real supply loading, not just wattage.
- Pair it with inrush current Ask for power factor together with inrush current. Both affect how the supply and protection must be sized for a clean start.
- Check correction is built in Confirm the correction is active inside the display's supplies, not left to site-side equipment. Built-in correction protects the building supply directly.
- Mind the utility limit Some supplies can lower the factor without correction; confirm the delivered value meets the site or utility expectation.
Common misconceptions
“Power factor only changes the electricity bill.” — Low power factor makes the supply deliver more current for the same work, oversizing feeders, breakers and cabling. It is an infrastructure cost, not just a billing line.
“All supplies are the same.” — Switched-mode supplies can lower the factor without correction. Quotes differ in whether correction is active and built in, which changes the real load on the building.
Key takeaway
Power factor is the share of drawn power that does useful work, from 0 to 1. An LED wall's switched-mode supplies can lower it without correction, making the supply deliver more current for the same work and oversizing the electrical build. Active correction in the power units raises the figure close to 1, and the value is confirmed on the delivered supplies and used to size the site feed.