What are Lumens (watts) ?
A ratio expressing the luminous efficacy of a light source. Typical lamp efficacies:
- Thomas Edison's first lamp - 1.4 lpW
- Incandescent lamps - 10-40
- Halogen incandescent lamps - 20-45
- Fluorescent lamps - 35-105
- Mercury lamps - 50-60
- Metal halide lamps - 60-120
- High-pressure sodium lamps - 60-140
Note: The values above for discharge lamps do not include the effect of the ballasts, which must be used with those lamps. Taking ballast losses into account reduces "system" or lamp-ballast efficacies typically by 10-20% depending upon the type of ballast used.