Luminous Efficacy


Definition of Luminous Efficacy

Luminous efficacy refers to how efficiently a light source produces visible light.

In other words, it's a measure of how much useful light you get for every watt of electricity you put in.

To calculate luminous efficacy, you need to measure the amount of light produced by the source in lumens and divide that by the power consumed in watts. The result will be expressed in lumens per watt (lm/W), which is the unit of measurement for luminous efficacy.

Luminous efficacy (lm/W) = Amount of light produced (in lumens) ÷ Power consumed (in watts)

The higher the luminous efficacy, the more energy-efficient the light source is, meaning less wasted energy and lower electricity consumption. Additionally, a higher luminous efficacy means a brighter light output for the same amount of electricity.

Both results make a big difference in the light fixtures chosen for applications, such as boat lighting, where brightness is important for safety and visibility, yet electricity is limited as most boats are battery powered.

In the table below, we look at the luminous efficacy of various bulbs and how that translated to application.

Type Of Light Bulb Luminous Efficacy (lm/W) Application
Halogen 100 W 16.7
Incandescent 100 W 17.5 Indoor ambient and accent lighting
Mercury arc lamp 50–55
  • Technical use e.g. UV curing
  • Outdoor lighting
Compact fluorescent 32 W 75
  • Recessed lighting
  • Ambient lighting
High intensity discharge lamp 65–115
  • Street lighting
  • Large scale indoor lighting e.g. in warehouses
LED lamp 120 V 102
  • Home lighting
  • Commercial and industrial lighting
  • Automotive lighting
  • Electronic displays.
  • Task lighting
  • Accent lighting
  • Landscape lighting
Low-pressure sodium lamp 100–200 Street lighting and other outdoor applications where accurate color rendering is not important, e.g. industrial spaces

Clearly, LED lights are top of class in both luminous efficacy and breadth of application, which is why Apex Lighting specializes in LED boat lighting.

Overall, understanding and using the concept of luminous efficacy can inform your choice of lighting solutions for your boat or any other application, allowing you to strike the right balance between brightness, energy efficiency, and cost-effectiveness.

Example of Luminous Efficacy in a Sentence

"The lux meter indicated that the workspace was brightly lit with an illuminance level of 1000 lux."

Related Terms for Luminous Efficacy