Lighting, LEDs & Electrical Fixtures worked example

Luminous Efficacy with fixture lumen output of 30,000 lm: a worked example

Push fixture lumen output up to 30,000 lm and the picture changes. This example computes every intermediate figure at that operating point. Use this when checking whether a fixture meets DLC Premium or ENERGY STAR efficacy thresholds, comparing efficacy across LED chip or driver combinations, evaluating a supplier's performance claims, or selecting between fixture options for a retrofit or new installation.

The inputs for this scenario

  • Fixture lumen output: 30,000 lm (raised for this scenario; the documented default is 12,000)
  • Fixture input power: 100 W (unchanged)
  • Efficacy scale factor: 1 x (unchanged)

Working through the calculation

  • Applying the documented formula (Luminous efficacy = fixture lumen output / fixture input power x scale factor) to the inputs above produces each figure below.
  • At this operating point the engine returns 300 lm/W for luminous efficacy (lm/w), the number this scenario is built around.
  • At this operating point the engine returns 300 value for lm/w before scale factor.
  • At this operating point the engine returns 1 x for conversion factor.
  • At this operating point the engine returns 100 value for fixture input power (w).

How this compares with the baseline

  • Against the tool's baseline example, where fixture lumen output sits at 12,000 lm and the headline result is 120 lm/W, this scenario comes in 150% above the baseline at 300 lm/W.
  • It computes fixture luminous efficacy in lumens per watt from rated lumen output and input power, with an optional scale factor. The value of this scenario is the size of the gap it exposes: that gap, priced out over a year, is the budget you can justify spending to close it.

Results at a glance

  • Luminous efficacy (lm/W): 300 lm/W (headline result)
  • Lm/W before scale factor: 300 value
  • Conversion factor: 1 x
  • Fixture input power (W): 100 value

Run it with your numbers

  • Every input above is editable in the live Luminous Efficacy calculator, which recalculates instantly and can be shared with the inputs intact.

Last reviewed 2026-05-12.