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LED Lumens to Watts Conversion – NEVER buy based on Watts (Revised 2019)

LED Lumens to Watts Conversion – NEVER buy based on Watts (Revised 2019)

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.

 

HID Bulb Picture

 

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.

  1. Initial Lumens: how many lumens will the fixture produce brand new
  2. L70 Lumens: how many hours will it take before the fixture produces 70% of the initial lumen value
  3. 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.  

Lumens Per Watt Image

 

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.  

  1. 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)
  2. 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 MyLEDLightingGuide, will assist you with a photometric and show you, using software, how the light levels could look when you convert to LED.
  3. 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.
LED Diodes Image

 

The Golden Rule: 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). 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.

How Many LED Watts Do I Need to Replace my Existing Lighting?

How Many LED Watts Do I Need to Replace my Existing Lighting?

We hear this question all the time. The unfortunate reality is “watts” is the wrong way to shop when you are replacing your existing lighting. You need to be focusing on “lumens”. In the world of LED Lighting, a watt is consumed by the LED product and light is produced, that light is called lumens. Some LED products are better at doing that than other products.

So it is important to understand that not all LED products are equal in terms of how efficient they are at converting watts to lumens. In technical terms, we call this lumens/watt.

 

Replacing 400W HID

Our LED Retrofit Kits are built to run between 145 and 165 lumens per watt. This means that for every watt consumed, they will produce 145 to 165 lumens.

So our 100W Retrofit kit at 155 lumens per watt produces 15,550 lumens. In contrast, a competitive retrofit product that uses older LED Chips is designed to run at 97 lumens per watt. This competitive Retrofit kit produces slightly over 13,000 lumens but needs 135W to do produce that amount of light.

So clearly watts is a poor gauge to determine what you would use to replace an existing light source. If a customer called both companies and asked “how many watts do I need to replace 400W Metal Halide”, we would say 100W, they would say 135W.

How is that customer supposed to make a decision? But even then, our 100W produces more lumens than their 135W product.

So when customers ask us how many ‘Watts” do I need to replace an existing light source, we always convert them to lumens.

However, there is one large elephant still left here that we need to talk about. And that is the discussion of efficiency. In the above example, our retrofits produce more light while consuming 35 less watts per unit.

This is important, because this is 35 less watts that you are consuming and paying for on your electricity bill. So efficiency does matter, because it means your electricity bill will be significantly less using the 100W Retrofit kit than our competitors 135W Retrofit kit.

So as with the discussion above, there is a vast difference between LED products being offered on the market today.

Read the specs, and educate yourself on lumens. The less watts you consume saves you money, the more efficient the light is means it will produce more light using less energy than less efficient models.

 

Should I Buy New fixtures or retrofit my existing Light Fixtures?

This is another interesting question. And over the years, we have seen some pretty interesting answers coming from some of our competitors. Those that sell new fixtures claim new fixtures are the way to go. Those that sell only Retrofit kits claim that retrofitting is the only way to go. Who is the LED Consumer going to believe?

 

Fortunately, MyLEDLightingGuide sells both new Commercial Lighting Fixtures and hid replacement kits and so we are not biased in helping our customer make this decision. Keep in mind one point as you make your decision. Retrofit Kits are typically less expensive than a brand new fixture because you are not paying for the cost of the fixture. You are also not paying for the disposal of the existing fixture.

We have also heard the stories about how LED performs better in a new fixture than they do if you retrofit an existing fixture. That’s an interesting argument. Fortunately, we have had cases where we have sent both new fixtures and retrofits to customers to “test” the different options. Based on our experience, we have not seen evidence where the new fixture “always” performs better or is preferred over the retrofit solution. In more cases than not, the correct LED solution wins because they are the right solution for their needs.

Also, some “new fixture” vendors would like for you to believe that retrofits do not last long or as long as their new fixtures. Some vendors like to claim that all product coming from overseas are cheap and made poorly. Here is what we believe to be true. Our products are currently in their 6th generation of production. They come with a 10 year warranty.

They are built with brand name LED Chips and Drivers.

Here are some points of discussion you should consider if you are debating whether you should retrofit or replace your existing fixtures.

If your fixtures are in relatively good shape, retrofitting is typically lower cost, all things considered. New fixtures are not cheap, and using your existing fixture will save you money, plus a Retrofit kit is less expensive to ship than a new fixture.

  • If you have a large investment in your LED Light fixtures, then retrofitting allows you to keep your fixtures but move over to the new technology. A good example of this is area lighting at car dealerships where the pole and light head are an architecturally matching pair. Replacing the head with a non-match led head does not make sense.
  • If your fixtures are old and deteriorating, then you should replace your fixtures. Our Retrofits are not water proof, and you could damage them if they get wet. The LED Drivers are typically waterproof (look for the IP rating on the label, it needs to say IP65, IP66 or IP67).
  • There are instances where we would always recommend new fixtures over retrofit. One instance would be for High Masts and most 1000W Metal Halide High Bay applications.
  • It takes slightly longer to retrofit a fixture than it does to replace it.
  • You have to account for the disposal of the bulb, ballast and fixture when you replace a fixture and account for the disposal of the bulb and ballast when you retrofit a fixture.
  • Retrofit solutions perform as well as new fixture solutions.
  • Retrofit solutions will last as long as new fixtures as long as the Retrofit kit is installed properly.
  • Regardless of what solution you choose, you need to review the specifications of the LED components.
  • You should always determine how many lumens you need to replace your existing fixture, NEVER purchase based on watts. Not all LED solutions produce the same lumen per watt output.
  • Pay special attention to the lumens per watt of a fixture. IT DOES MATTER. A LED product at 135 lumens/watt will consume far less energy than a LED product producing 97 lumens/watt. Not all LED solutions are the same. (remember, always buy on the lumens you need, never on the watts you think you need.)
  • To calculate lumens per watt, take the total number of lumens a product produces and divide it by the watts it consumes.

 

Lumen Guidelines

Indoor fixtures

250W HID10,000 – 14,000 LED Lumens
400W HID15,000 – 25,000 LED Lumens
1000W HID38,000+ LED Lumens

 

Outdoor fixtures

250W HID7,000 to 10,000 LED Lumens
400W HID12,000 to 16,000 LED Lumens
1000W HID38,000+ LED Lumens

 

  • Our most powerful Retrofit kit produces over 50,000 lumens, our most powerful new fixture produces over 117,000 lumens.
  • We have new LED Lighting fixtures that can replace from 100-1000W HID, we have retrofits that can replace from 100-1000W HID.
  • Pay special attention to the lumens per watt of the LED fixture or retrofit. IT DOES MATTER. A LED product at 150 lumens/watt will consume far less energy than a LED product producing 97 lumens/watt. Not all LED are the same. (remember, always buy on the lumens you need, never on the watts you think you need.)
  • To calculate lumens per watt, take the total number of lumens a product produces and divide it by the watts it consumes.
  • You can get rebates for both new fixtures and Retrofit kits. Make sure they are DLC Qualified. That is the key to getting rebates with your utility company. You can check if a product is DLC Qualified on the DesignLights Consortium website. DLC has rebates for LED Lights.
  • Rebates with DLC Premium should be higher than rebates with DLC Standard. Your utility company is typically who provides the rebates and sets the rebate amounts.  Check their website.
  • All DLC Products are warrantied for at least 5 years.
  • All our LED Fixtures and Retrofit Lighting are either UL Listed or ETL Listed.
  • Replacing the light parts of an existing fixture with the a Retrofit unit will not void the UL/ETL Listing of the fixture.
  • ETL Listing is the same as UL Listing. They perform the same test, and the certification is the same. The only difference is that the company who performs the test.

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