How to Convert Incandescent Watts to LED Watts

Watts are are a measurement of energy. Watts most commonly measure electrical power. Watts could be used to measure optical power, but they just aren't very useful when talking about lighting because they consider all light energy to be equivalent, even wavelengths that are not easily seen by the human eye. The unit of measure for lighting is the lumen. Lumens measure the amount of usable light, which is light visible to the human eye. Still, there are conversions possible to compare incandescent to LED performance.

LED bulb
Incandescent bulb

Instructions

- 1
  Identify the wattage of each of the bulbs. Both LED and incandescent bulb will have an electrical power rating. For example, an incandescent bulb marked 60W uses 60 watts. On the EnergyStar LED product website, the LED ECS19WW bulb from Lighting Sciences Group uses 7.7 watts. The EnergyStar website maintains a website containing the information you'll need for all approved LED products, or you can look at the "LightingFacts" website or label on the package.
- 2
  Find the light output of each of the bulbs. Again, from the EnergyStar websites, you can learn that a 60 watt incandescent puts out about 800 lumens and a LED ECS19WW bulb, for example, puts out 385 lumens.
- 3
  
  LED bulbs are generally far more efficient than incandescents.
  
  Calculate the lumens per watt for each bulb. Lumens per watt is a measure called efficacy, which measures how efficiently the bulb converts electricity to usable light. The efficacy of the incandescent is about 13 lumens per watt, while the ECS19WW is 50 lumens per watt.
- 4
  Complete the comparison by determining how many watts would be needed to light your application. For example, if you find the light from two 60-watt bulbs to be more than sufficient to illuminate an area, you'll need about 1600 lumens. Four of the ECS19WW bulbs provide 1540 lumens, a negligible difference of only 60 lumens. Two 60-watt incandescent bulbs use 120 watts, while four LED ECS19WW bulbs use only about 31 watts.

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