Definition
Luminous efficacy (measured in lumens per watt, lm/W) is the most important efficiency metric in LED lighting — it measures how effectively a light source converts electrical power (watts) into visible light (lumens). Two types must be distinguished: (1) Source/chip efficacy: measured at the LED component level before optical and driver losses, and (2) System/luminaire efficacy: measured from the complete fixture including driver efficiency and optical transmission losses. System efficacy is always 10-25% lower than chip efficacy. For B2B procurement, always specify system efficacy — it's what you actually pay for in electricity and what determines energy code compliance. LED system efficacy has improved from ~60 lm/W (2010) to 130-200+ lm/W (2026), representing the most significant technological advancement in lighting history.
Key Data
| Parameter | Value / Explanation |
|---|---|
| Incandescent | 10-18 lm/W — 90% of energy wasted as heat. Phased out globally. |
| Halogen | 15-25 lm/W — slightly better incandescent. Also phased out. |
| CFL (compact fluorescent) | 50-70 lm/W — mercury-containing, warm-up delay. Largely replaced by LED. |
| Fluorescent tube (T8/T5) | 80-100 lm/W — still common in existing installations; being retrofitted to LED. |
| LED (standard 2026) | 100-140 lm/W system — mainstream commercial grade. |
| LED (premium/DLC Premium) | 140-180 lm/W system — qualifies for maximum utility rebates. |
| LED (cutting-edge 2026) | 180-220 lm/W — premium architectural and specialty applications. |
Application Guide
Warehouse retrofit
≥150 lm/W system, DLC Premium, 200-300W UFO high bay
Energy is 60-80% of warehouse operating cost; every 10 lm/W improvement saves ~6% energy
Office new construction
≥130 lm/W system, UGR ≤19, 4000K, DALI-2 dimming
Meets ASHRAE 90.1-2022 and Title 24; maximizes energy code compliance and utility incentives
Budget retrofit
≥100 lm/W system minimum — below this, payback extends beyond 3 years
At $0.12/kWh, the 30 lm/W gap between 100 and 130 lm/W represents ~$3/fixture/year
Conclusion & Procurement Recommendation
For B2B procurement, efficacy determines your electricity bill for the next 10-15 years. Key specification requirements: (1) Always request system (luminaire) efficacy per IES LM-79, not chip efficacy, (2) For projects >100 fixtures: the 20-30 lm/W difference between a 100 lm/W and 130 lm/W fixture saves $3,000-8,000/year in electricity (at $0.12/kWh, 5,000h/yr), (3) DLC Premium qualification requires minimum efficacy thresholds by category — always check the current DLC Technical Requirements table, (4) Verify efficacy at the actual operating CCT and CRI — efficacy drops 10-15% when moving from 5000K CRI 70 (maximum efficiency) to 3000K CRI 90 (typical architectural specification).