We all know or at least heard that converting from Metal Halide (High Intensity Discharge) to LED will save you money. But how much? Are there any other reasons or difference you should know about with LED vs Metal Halide lights?
In this article, we break down all the factors that you should be aware of before making a decision to convert from Metal Halide to LED. Here are the 9 reasons we think LED wins over Metal Halide.
1. Lamp (Source) Efficiency Vs Fixture (System) Efficiency
Let’s take a look at the information on a typical 400 watt metal halide bulb. While specifications may vary, a visit to a popular online website that sells Metal Halide bulbs shows that a brand new bulb has the following specifications:
- Color Temperature: 4000K
- Initial Lumens: 32,000 to 36,000
- Life Hours: 20,000
A recent white paper by the Dark Sky Society rated the mean lumens for a 400W Metal Halide to be 20,500 lumens and the rated life expectancy to be around 15,000 hours. But for purposes of this discussion, we will stick with the numbers we are familiar with.
There is a lot of interesting information to look at. Initial lumens is a very high number, but in reality, a Metal Halide bulb starts off very bright and then drops its lumens rather quickly, settling in at a lower lumen output rather quickly. It is not uncommon to lose as much as 20% in the first 6 months alone. So while 36,000 lumens sounds impressive, within 6 months, it can be below 30,000 lumens. Lumen depreciation in a metal halide bulb is relatively quick. It is noted that at half life of the bulb, around 8,000-10,000 hours, lumen depreciation is already at 50%.
Similarly, let’s look at the operating nature of the bulb. A Metal Halide bulb is omni-directional. That means light is distributed in every direction. So it produces as much light horizontally parallel to the ground as it does facing downwards.
To make this light useful, you need to gather it, collect it, and deliver it to where you want it. In fixture design, you add a reflector to do this job. The main problem with reflected light is how effective is the reflector getting the light that bounces off of it to the ground. A lumen that bounces off the reflector and bounces back into the fixture is considered a loss lumen. Anything more than one bounce is throw-away. As much as 30% or greater of the light can be lost in this reflective bounce. So if we do the math of a metal halide bulb in an industrial indoor bay fixture, if we assume the initial lumens of the lamp at 36,000 lumens, after 6 months we would expect the fixture effective lumen efficiency to be:
36,000 lumens – 20% (initial lumen loss) = 28,800 lumens
Lumens loss from reflector bounce: 8,640
Total lumens after 6 months in indoor bay fixture: 20,160
This does not take into account any lenses or shields that the fixture might already have. Keep in mind, this is bulb lumens, not fixture lumens, so anything else added that gets in the way of getting light to the ground will always take away from effective lumens.
Compare this to LED. If you think of a LED fixture or one of our LED Retrofit Kits that replaces MH and HID technology, all the light is directional, in that, it is directed to where it is needed. Reflectors are not required. There is nothing to reflect. In terms of lumen depreciation, it does happen in LED, but it takes a lot longer for it to happen. For example, our retrofits have a L70 (lumen depreciation to 70% of initial lumens) of over 100,000 hours. So where as Metal Halide loses a lot of lumens in the first 6 months of life, LED tends to maintain its lumens for a lot longer.
2. Operating Life
As mentioned, the operating life of a typical Metal Halide bulb seems to be around 20,000 hours. Larger bulbs, like a 1000 watt Metal Halide, are around 15,000 hours. In terms of LED solutions, there are different ways suppliers describe the life of the product. One way is to mention L70. L70 is not a measurement of end of life, but it is a measurement of lumen degradation up to 70% of initial lumens. This does not mean the driver or ballast or some other component might fail prematurely.
What we do know is the life of a Metal Halide bulb is around 15,000 to 20,000 hours. What we also know is that at half life, it has already lost 50% of its initial lumens. So while not dead, highly ineffective. For the record, it still consumes 400+ watts even though it is half as bright.
Compare that to our Retrofit Products rated at 100,000 hours (L70). So by the time the LED head reaches 100,000 hours, you have done 5 Metal Halide bulb replacements, possibly more.
3. Efficiency (lumens/watt)
This is the pre-cursor to the next topic, energy savings, but the basic premise is the more efficient the bulb is, the more money you will save. So let’s calculate the lumen efficiency of metal halide versus LED.
To calculate lumen efficiency, you need to take the total lumens produced and divide it by the total watts consumed. In the case of Metal Halide, you also have to include ballast draw. If you recorded the total watts consumed of a typical 400W bulb, it is around 455 watts. The ballast consumes about 15% more energy over and above the bulb consumption.
So calculating lumen efficiency for metal halide: 36,000 lumens / 455 watts = 79.12 lumens/watt.
Let’s compare that with our 150 watt Retrofit Unit: 23,250 lumens / 150 watts = 155 lumens/watt. Almost double of Metal Halide.
And remember the golden rule: Efficiency Saves Money!
4. LED vs Metal Halide Energy Savings
So in the above discussion, something important was pointed out. Above we talked about the mean lumens of a 400W Metal Halide to be around 20,500 lumens. Our 150W retrofit kit produces 23,250 lumens, but instead of burning 455 watts, it consumes only 150 watts. That represents a 66% savings in energy consumed to produce more light. But the truth of the matter, we think 23,250 lumens to replace 400W Metal Halide is over kill. For years, we have been selling our 105W Retrofit and it’s more efficient replacement, the 100W retrofit at 15,500 lumens to replace 400W Metal Halide. Here is a recent example of a trial a customer did to make sure the lumen output of our 105W kit would be as good as what he was currently using.
Notice: in the comparison picture below, the LED produces so much light it casts a shadow from the pole in the light generated by the metal halide light.
5. Savings on Maintenance
We have just as many customers wanting to convert to LED because of maintenance savings as they do for energy savings. Think about what we discussed, over the life of the LED product, a customer would have to do 5-6 bulb replacements. The higher the installation height, the higher the cost of replacement. And if you have a facility loaded with lights, this becomes a significant budget amount every year that you must take into consideration. Now, we know that reduced maintenance time on lights does not translate into dollars saved because it is highly unlikely that people will lose their jobs over the fact there is much less work to do. However, these people will have time to now work on things that matter, like fixing the machines that make the company money instead on replacing lights that cost the company money.
Read Part 2 of this Post for Reasons 6 – 9