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This is a common message we try and teach our customers when they call us. For example, it is not uncommon for us to get a call to quote a price on a LED Product, and being told they need a price on a 150W LED Fixture. The most important thing we can do for our customers is to explain LED efficiency. Read this post to discover the right way to pick the right LED product.

What are Watts?

Watts are simply a measurement of consuming energy. When you pay the utility bill, the bill represents a charge for the amount of watts, or energy, you used. A 400W Metal Halide Shop Lights consumes 400W of energy. What it doesn’t represent is the amount of light, or lumens, produced. Although, over time, we begin to associate light levels with the bulb being used. So we say “We want the brightness of a 400W MH Bulb”. What we really are discussing is the amount of visible light produced by the bulb which consumes 400W.

What are Lumens?

Simply, a lumen is a measurement of visible light. The more lumens you have, the brighter the light will appear. Most companies will tell you three important facts about lumens.

Initial Lumens: how many lumens will the fixture produce brand new 

L70 Lumens: how many hours will it take before the fixture produces 70% of the initial lumen value

Lifetime of fixture: this is typically the expected life (before complete failure) of the fixture, or how long you can expect the fixture to operate without the need for maintenance. 

Understanding Lumens / Watt or Efficacy

The key to this discussion is understanding lumens per watt or efficacy.  This is a measurement of how efficiently a light source converts watts into lumens. Old technology like Metal Halide have an efficiency of about 80 lumens per watt. So it takes 400 watts to produce 32,000 lumens.

LED, on the other hand, is significantly more efficient, with levels approaching 200 lumens per watt. For example, we have LED retrofit kits that produce light at 165 lumens per watt, over 2X as efficient as the metal halide bulb it replaces.

However, here’s the catch. Not all LED products have the same efficiency. In fact, the variance can be rather dramatic.

A LED fixture at 100 lm/W needs 200 watts to produce 20,000 lumens

A more efficient LED at 150 lm/W needs only 133 watts to produce 20,000 lumens

So when buying LED, its really important to understand the efficacy of the fixture when comparing products.


How to determine the best LED fixture that consumes the least amount of energy

So lets say you are in the market to replace your existing lighting. Here are the steps to follow.

Determine how many lumens you need. How do you do this? Take a foot candle reading at your location, and determine if that is the right amount of light. (it can be raised or lowered – and now is the time to do this)


Now you know the average foot candles, determine how many lumens you need to produce this amount of light to meet your foot candle requirement. A reputable company, such as LEDLightingSupply, will assist you with a photometric and show you, using software, how the light levels could look when you convert to LED.


Pick the fixture with the highest efficacy to produce those lumens. The watts consumed by the fixture is the energy consumption that you will now lower your utility bill to.

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Remember: Buy Cheap – Buy Twice

Let’s make one point clear, we are very competitive with our pricing. But we get a lot of customers calling us to fix their cheap LED purchase problems (purchased elsewhere). A cheap product is typically inefficient and has a low lumens / watt efficiency.

Those problems consist of lights that have broken or aren’t what they thought they were buying. So we understand, everyone wants a bargain. But be careful of low priced products – its cheap for a reason.

Dwayne Kula


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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.

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