Formula variables
- Lumens are the light output target entered by the user.
- Efficacy is fixture lumens per watt.
- Driver allowance is an optional percentage added for preliminary electrical load planning.
- Estimated watts are for planning and should be replaced by actual fixture input watts when selected.
Assumptions
- Fixture efficacy is entered in lumens per watt.
- Driver allowance is added after base LED watts are calculated.
- The result is a planning load estimate, not a fixture schedule or lighting design.
- Manufacturer photometric data, driver input watts, dimming, temperature, and layout still govern final selection.
Examples
12,000 lumen fixture group. At 130 lm/W plus a 10 percent driver allowance, 12,000 lumens estimates about 101.5 W.
Panel schedule use. Use actual fixture input watts from the submittal before final branch-circuit and load schedule review.