Why every LED buying decision should include lumens per watt
When you compare LED fittings, the wattage on the box is only half the story. Two fittings of the same wattage can give very different amounts of light. The number that tells you how efficient a fitting is, is lumens per watt (lm/W), also called efficacy.
Watts, lumens and lm/W
- Watts (W): the power the fitting draws. This drives your electricity bill.
- Lumens (lm): the amount of light the fitting gives out.
- Lumens per watt (lm/W): lumens divided by watts. The higher it is, the more light you get for each unit of power.
A worked example
PS-UFO-MAX gives 40,000 lumens at 200 W: 40,000 / 200 = 200 lm/W. A fitting giving the same 40,000 lumens at 150 lm/W would need 40,000 / 150 = about 267 W. For the same light, that is roughly a third more power, every hour the lights are on.
What to ask for in a quote
- Fitting lumens, not chip lumens. Chip figures ignore losses in the optic and driver.
- The lm/W of the complete fitting, at the wattage you will actually run.
- Lumen maintenance over time, for example L80B10 >50,000 h to TM-21 (as stated for PS-UFO-MAX).
- The optic. In racking aisles an aisle optic such as the 30 x 90° lens on PS-CURVE puts light where it is needed, so you may need fewer lumens overall.
- Controls. Sensors reduce the hours a fitting runs, which multiplies the effect of high efficacy.
Efficacy is not everything
Glare, colour rendering and build quality matter too. Where people look up, a low glare fitting such as PS-MILD (UGR below 19) may be the better choice. For sports pitches, beam control matters as much as efficacy.
Get a like-for-like comparison
Send us your current fittings and drawings, and we will give you a lux design with fitting lumens, lm/W and energy use per zone, backed by a 5-year warranty.