5 Steps To Calculate Total Fixture Wattage For Metal Halide Fixtures

Posted by Jimmy Hovey on Tue, Mar 20, 2012 @ 20:03 PM

Metal Halide Fixtures Are Some Of The Most INEFFICIENT Lighting Options Available....Do You Have Some?

Metal halide fixtures are still being specified into projects even though they are one of the worse possible options when considering upgrading your lighting.

I am not sure why the Contractors, Utilities, Engineers and Lighting designers can't get together, but just in case you are considering a project with Metal Halide, you will be want to compare your total fixture wattage against some other options.  

Your goal should be to get the best possible lighting for your application for the lowest cost of operation and maintenance over the life of the lighting system. 

Step 1 - Determine If You Have Metal Halidemetal-halide-fixtures-400-watt-metal-halide-bulb Fixtures

In order to calculate your total fixture wattage, you need to know what kind of fixture you have.  

There are numerous variables, but typically we see a lot of 400 watt metal halides in the facilities we are in.  That is most common in warehouses, retail stores, and gymnasiums. 

We have even seen the 1000 watt metal halides in interior applications. 

On the exterior, expect to find 250 watt and 175 watt metal halides as the most prevalent.  As you can see from the extensive range of options, it is important to know what your wattage is to get accurate calculations. 

Step 2 - Identify The Type Of Fixture You Have

There are primarily 4 types of metal halide fixtures;400-watt-metal-halide-fixtures-hovey-electric

They are:

  • High-bay
  • Low-bay
  • Shoe box
  • Wall packs
The type of fixture is usually a good indicator of the type of wattage.  Higher wattage fixture are used where you need ALOT of light; think of baseball fields.  Lower wattages are used in parking lots and building perimeters. 

Step 3 - You Need To Know How Many Fixtures You Have

Once you have identified the type of fixture you have in your facility(you may have many types) total up the number of each type in each area. 

If you have a lot of fixtures to count, get some help. You can easily get lost in your count walking around looking up in the ceiling (oh ya, don't trip on anything either!)

Now that you have your fixture count, you are ready to calculate your total wattage. 

Step 4 - Identify the Wattage for Each Type of Metal Halide Fixtures

There are basic a couple of different ways to figure out the wattage of the fixtures in your facility.  One is complicated and the other is not so complicated. 

You don't have to be exact when determining your fixture wattage.  You should be able to determine from a distance what the type of fixture is and then determine the wattage. From there you can use averages like the ones that we use when doing an energy efficiency assessment. 

Here are the fixture wattages that we typically use:

  • 1000 Watt Metal Halide is rated for 1081 Watts

  • 400 Watt Metal Halide is rated for 458 Watts

  • 250 Watt Metal Halide is rated for 290 Watts

  • 175 Watt Metal Halide is rated for 205 Watts

By using the averages, we are able to get a good comparison against newer technologies with lower fixture wattages.

Step 5 - Multiply Your Quantity of Fixtures by the Wattage of Your Existing Fixture.

Just take the information from each step above and list out the data that you have.  That way the final step is pretty easy.  You can do this by hand, but if you have a lot of different types of fixtures I would suggest using a spreadsheet. 

So let's look at an example project and assume you found the following in each of the steps;

Step 1 - You have Metal Halide

Step 2 - You have 1000 watt high bays

Step 3 - There are 100 fixtures

Step 4 - Your wattage is 1081 watts per fixture

Step 5 - (This step....)

Simple math....

Take 100 fixtures x 1038 watts = 103,800 Total Fixture Wattage

If you have more than one type of fixture, you just simply repeat Steps 1 - 5 to get the total wattage of your entire facility.

Note: You can easily replace a 1000 watt metal halide with an inductive lighting option that is 250 watts.  So in this example, your total fixture wattage would be 25,000 watts instead of 103,800.  We know it works, we have replaced 1000 watt metal halide fixtures with 250 watt induction lighting.

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Energy Efficient Lighting:400 Watt Metal Halide vs. T-5 Retrofit

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Topics: metal halide fixtures, fixture wattage, calculating wattage, how to calculate watts, metal halide, 400 watt metal halide, wattage