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Watts, Lumens or Foot Candles – As a lighting consumer which one is the most important
In the world of lighting, there are three primary measurements: Watts, Lumens, and Foot Candles. These three factors make a profound impact on how we perceive and function within our indoor and outdoor spaces. These three primary specifications of lighting help define the performance of light and how they will affect your space. They are the building blocks of how well a LED Lighting fixture will perform, and in turn, help guide your buying decisions.
But what are these measurements? Why do they matter? Which should you pay the most attention to in your purchasing decision? Here’s a quick guide to these three lighting terms.
Watts
Watts is the measurement you are most familiar with. Before LED, it was basically the way we chose light bulbs.
However, wattage refers to the amount of energy a light bulb consumes. It is not a measurement of brightness. It should not be the basis of how you choose a LED fixture if you are simply thinking watts = brightness. Wattage is going to effect your pocket book. Our utility companies charge us based on energy usage, and the more “watts” a fixture is rated at, the higher the bill. That is basically why a 150 Watt LED fixture saves you money when it replaces a 400 Watt Metal Halide fixture.
Lumens (and Lumens per Watt)
Lumens is a measurement of light output or brightness. Watts is the price you pay for light. Lumens is what is delivered from a fixture or bulb based on the watts consumed.
So another term you need to pay attention to is Lumens per Watt. This is a measurement of how many lumens is produced from 1 watt consumed. For consumers, look for a higher number. So 200 lumens per watt is better than 100 lumens per watt.
Let me put this another way. Let’s compare 2 fixtures:
- 200 Watt LED Fixture at 100 lumens per watt = 20,000 total lumens
- 100 Watt LED Fixture at 200 lumens per watt = 20,000 total lumens
Both lights produce 20,000 lumens, the second light consumes 1/2 the watts to produce the same amount of light. And from the above discussion, this means you will have lower utility bills.
Here is the trap most consumers don’t realize. In the above example, the second fixture will be more expensive than the first. So they purchase the first fixture because they think they are saving money. The truth of the matter, over the life of the fixtures, the far better deal is going to be the purchase of the second fixture. The energy savings alone will be much better and will far outweigh any additional cost of purchasing the more efficient light.
Foot Candles (Lux)
Foot candles is a measurement of all the lights in a space and the brightness of the space. Foot candles measures illuminance. Illuminance is the amount of light received on a surface. It is equivalent to one lumen per square foot. So when we are asked to do a commercial, industrial or sports field lighting plan, one of the most important questions we ask is “How bright do you want the space?” This is always a measurement of foot candles. The higher the number, the brighter the space.
Lux is another way of measuring brightness. There are those who think in terms of brightness in terms of foot candles, and some who thing in terms of lux. Both are acceptable.
Which measurement is the most important for customers looking to buy lighting?
It truly depends on your needs and your application.
For energy efficiency, look at Watts
For brightness, consider Lumens
For understanding how well a space is lit, foot candles is your measurement.
For more information, please visit our blog for similar articles:
What does it take to replace 400 Watt metal halide?
What does it take to replace 1000 Watt metal halide?
What does it take to replace 1500 to 2000 Watt metal halide?
Watts, Lumens or Foot Candles – As a lighting consumer which one is the most important
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About the Author
Dwayne Kula is President of LED Lighting Supply. On any given day, Dwayne is writing content for the site and helps manage the marketing initiatives that are on-going. He has a Software Engineering degree and still dabbles in writing software for the company as needed. When not working, he enjoys spending time with his family, working out, playing the occasional game of golf and exploring New England.