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How To Calculate Lighting Costs For Metal Halide Fixtures

 

I See New Metal Halide Fixtures Are Going In Daily.....Despite The High Annual Cost Of Operation....

how to calculate the cost of metal halide fixtures

Every day I drive by new construction sites and just shake my head in disgust. 

Why is that? 

I still see new metal halide fixtures being installed everywhere. 

In Kentucky, I have even seen a utility, who is paying out incentives to business to get rid of their metal halide fixtures, are still putting up metal halide fixtures to light up their streets. 

It is ridiculous because I have done the calculations on how much it costs to operate these metal halide fixtures. 

The upfront costs may be low, but once you factor in maintenance and the cost of electricity, the metal halide fixture is one of the worst possible options you could use to light up your facility or grounds around your building.

Don't believe me? 

Get out a piece of paper and calculator and follow along.....

How Do Calculate The Energy Cost Of A 400 Watt Metal Halide

1. How Many Watts?

In order to determine the watts that your fixture uses, you must determine what size your metal halide fixture is.  Once you determine that, you can then find the "actual" watts that the fixture uses. 

Here is a list of metal halide's we typically see.  Figure out which one you have and choose the actual wattage on the right.

  • 175 Watt Metal Halide  Fixture = 205 Actual Watts
  • 250 Watt Metal Halide Fixture =290 Actual Watts
  • 400 Watt Metal Halide Fixture = 458 Actual Watts
  • 1000 Watt Metal Halide Fixture =1,081 Actual Watts

2. How Many Fixtures?

Now that you have the watts, you have to determine how many fixture you have.  This is one of the easier steps in calculating your lighting costs unless you have a lot of fixtures. 

If you have a lot, you may want to have someone help you take a count.  It is easy to lose track with your neck bent looking straight up at the ceiling (...plus you don't want to walk into anything and bump your head!)

3. How Many Total Watts?

This is simply the number of fixtures multiplied by the number of watts for your type of fixture.  So if you have 20 - 400 watt metal halides, you would simply multiply the following:

20 fixtures x 458 watts = 9,160 Total Watts

4. How Many Kilowatts?

Now take your total watts and divide by 1000 to get your total kilowatts.  Using the example from above:

9,160 Total Watts / 1,000 = 9.16 Kilowatts

5. How Many Hours Are Your Lights On Each Day?

This is relatively simple to calculate.  But here is a chart for quick reference.  It is easiest to go by the type of shifts you have for your company, you don't have to be exact here, just close.

Here are the most common total hours per year;

  • 8 hrs per day = 2,000 hours per year
  • 10 hrs per day = 2,500 hours per year
  • 12 hrs per day = 3,000 hours per year
  • 16 hrs per day = 4,000 hours per year
  • 24 hrs per day = 6,000 hours per year

For our example, we will choose 12 hours per day, or roughly 3,000 hours per year that our 400 Watt Metal Halide's are lit up. 

6. To find Kilowatt/Hours (Kwh) we multiply;

9.16 Kilowatts x 3,000 hours per year = 27,800 Kwh

7. What Is The Cost of Your Energy?

27,480 x .08 = $2,198 per year in annual energy costs

8. How Much Per Each 400 Watt Metal Halide?

$2,198 / 20 = $109.20 per year/per 400 Watt Metal Halide

Cut Your Annual Energy By 50% Or More With New Technologies

There are many technologies available that can easily cut that number in half.  We have covered the topic very thoroughly here on our blog, so I thought you might want a little help in locating related articles.

What's Cheaper To Maintain...400W Metal Halide Or T5?

Metal Halide Fixtures:Does A Fixture Use Power With The Bulb Removed?

How To Reduce Wattage In Sensitive Areas Requiring Hazardous Lighting

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

Maintenance Cost Comparison:400 Watt Metal Halide vs.Fluorescent T5

How To Reduce Gymnasium Lighting Cost By Over 50%.....Real Project

Learn More About Energy Efficiency...

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Comments

I see the same thing here in the Pacific Northwest. It really is a shame that people don't know about all of the better options they have out there.
Posted @ Friday, July 27, 2012 1:44 PM by Jordan
the math does not add up. 9.16 not 91.6
Posted @ Monday, December 17, 2012 6:33 PM by
has anybody pointed out that, regarding your 400w metal halide example that 9160 watts divided by 1000 equal, in fact, 9.16 kw? also, real metal halide watts calc for 400w is about 458 watts and 12hr/day x 365 days/yr = 4380 hrs. (exterior lighting on photocell.
Posted @ Wednesday, December 19, 2012 6:28 PM by MICHAEL T ROBERTS ELECTRIC
Make sure you fully understand the math before making these statements and "advising" the public. For your example, you are looking at an annual cost of $110 per luminaire...you're off by a factor of 10 since you converted watts to kw incorrectly. LED is still expensive and people don't want to wait 10+ years for payback on their investment. This is why you still see metal halide installations.
Posted @ Wednesday, March 13, 2013 11:38 AM by Eric
Wow...no one actually looked at lumens produced, plus this guys math is way off as someone already noted. This is what make me a little angry, it really shows they don't know what they are talking about. Show me a replacement LED fiture to a equivalent 400w MH fixture that produces the same lumen output. A typical 400 watt MH bulb puts out almost 30,000 lumens, so at 458 watts that is 65.5 lumens per watt. Most LED and CFL are not that efficent, although they do have smaller bulbs that are. In other words the public utilities still put them in because they are very efficient. It makes sense to put LED's into street lights and stop lights because of the high cost of maintenance (replacing bulbs) in these areas.
Posted @ Saturday, April 20, 2013 8:09 PM by Jesse
You cannot match lumen for lumen when replacing MH with LED. Seattle did this when they first started replacing their streetlights back in 2007 and they got all kinds of complaints that there was too much light. 
 
In a typical MH or HPS fixture there is a lot of trapped light that never gets to the ground. In an LED fixture virtually 100% of the light hits the surface you are trying to illuminate because of the direction nature of LEDs. You can typically get by with 1/4 to 1/3 the lumen output and have better light on the ground. All you have to do is see an actual LED installation to understand what I am talking about.
Posted @ Wednesday, June 05, 2013 3:30 PM by Steve
I apologize, the math was off by 1 decimal point. But even with the math off, the point is Metal Halide is still an out of date technology. If you made the same mistake with comparative technologies, it would still show the cost at 1/2 the operating costs of MH. I corrected the math for all of those who emailed me, thanks again for pointing that out.
Posted @ Wednesday, July 31, 2013 3:04 PM by Jimmy Hovey
LED technology is advancing so quickly that you can easily lose track of the latest advances. For example, the DOE just released another Gateway report on an LED streetlight installation, this one in Kansas City. An LED streetlight demonstrated a real-world net efficacy of 83 lumens per watt, compared to the 45 lpw of HPS. The trick (as others have noted) comes in the much higher fixture efficiency possible with LEDs (because who really cares how high your bulb efficacy is if you can't get those lumens on the ground?). Then add in the increased uniformity — which means you don't need to have a huge hot spot right underneath your pole just to maintain illumination levels between poles. Then throw in the increased visibility because of better color rendition and you can see that you don't need anywhere near the lumens of an HPS or MH bulb to effectively light the streets...not to mention an entire new level of savings possible with intelligent/adaptive controls, just beginning to be demonstrated.
Posted @ Wednesday, September 18, 2013 11:16 PM by richard gaughan
There are quality LED Lamps pushing 130 Lumens Per watt. I have replaced 400w and even 1000wMH with LEDs with excellent results. We will be installing 2000w equivalent LED lamps in the next 2 weeks. I have a 237W LED 45ft. from the floor emitting 30+FC on the floor.
Posted @ Thursday, December 05, 2013 10:13 AM by Darrel
Dear Jimmy, 
 
You are doing a great service by raising the awareness level about need for Energy Efficiency in our systems to enhance sustainability of our planet. Ever grateful.
Posted @ Sunday, July 27, 2014 10:16 PM by Rajive
LED saves power, but can it be used in dusty area like Rolling mill or ceramic industry ?...Because here the dusts are sticky and will block the luminous and may create problem in maintenance..
Posted @ Monday, August 25, 2014 11:14 AM by syed ibrahim
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