In this article we break down the factors to be aware of before deciding to convert from Metal Halide to LED. Here are the 9 reasons 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. A popular online website shows the specifications a new Metal Halide bulb:
- Color Temperature: 4000K
- Initial Lumens: 32,000 to 36,000
- Life Hours: 20,000
A white paper by the Dark Sky Society rated the mean lumens for a 400W Metal Halide to be 20,500 lumens. 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. 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 quick. At half life of the bulb, around 8,000-10,000 hours, lumen depreciation is already at 50%.
Let’s look at the operating nature of the bulb. A Metal Halide bulb is omni-directional. That means light distribution in every direction. So it produces as much light 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 issue is how effective the reflector is at bouncing light downward. A lumen that bounces off the reflector and bounces back into the fixture a lost lumen. Anything more than one bounce is throw-away. You can lose as much as 30% or greater of the light in this reflective bounce. So lets do the math of a metal halide bulb. In an industrial indoor bay fixture, 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: 8,640Total 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 that gets in the way of moving 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 HID, all the light is directional. Reflectors are not required. There is nothing to reflect. 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. 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. 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.
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, it’s 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 or more Metal Halide bulb replacements.
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.
Here’s how to calculate lumen efficiency. 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.
Remember the golden rule: Efficiency Saves Money!
4. LED vs Metal Halide Energy Savings
In the above discussion, lets point out something important. 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, 23,250 lumens to replace 400W Metal Halide is over kill. For years, we have been selling our 100W HID Retrofit at 15,500 lumens to replace 400W Metal Halide. Here is a recent example by a customer did. He wanted to compare our retrofit kit vs his existing Metal Halide fixture.
In the comparison picture below, the LED produces enough light to cast a shadow from the pole in the light generated by the metal halide light.
5. Savings on Maintenance
We have many customers who convert to LED because of maintenance 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. If you have a facility loaded with lights, this can be a significant recurring cost every year.
Reduced maintenance time on lights do not translate into dollars saved. This is because it is unlikely that people will lose their jobs over the fact there is much less work to do. These people will have time to focus on other tasks. Focusing on more important maintenance can be very important to any business.
6. Quality of Light
When you take a measurement of light with a light meter, it reads lumens. Foot candle is a measurement of all the fixture contributing to light at a location. But let’s think about that light that is being measured. Metal Halide creates all sorts of light, in all spectrum’s, visible or otherwise. This includes UV and IR spectrum’s, visible to the measuring device but not visible to the human eye. LED does not produce UV and IR. Light produced by LED is all visible to the human eye.
So there is a fun little test you can do. Have 2 light sources, LED and Metal Halide. And first ask, which one is brighter? In many instances, it should be the LED Light source. And then use a light meter, and the light meter may say the Metal Halide area is producing more foot candles. And so now you know part of the reason, but wait, there’s 2 other pieces of information you need to know.
One is Color Rendering Index, or CRI. It is a measurement of Quality of Light. It’s a scale between 0 and 100, 100 is excellent. And LED tends to have a high CRI value. So the other golden rule we say is “You need less quantity when you have more quality”. Metal Halide bulbs can be good, and are much better than High Pressure Sodium. But LED tends to be much better, so we perceive the light generated by LED to be brighter. More about this in the next section.
7. Photopic vs Scotopic Lumens
Many years ago, the discussion of photopic vs scotopic lumens as voodoo magic talk. There were those who believed in the difference and as many who discounted it. This is a discussion of how humans see light (scotopic) vs how a light meter perceives light (photopic). It is true people are able to see, and light is a big part of why we are able to see. Walk into a dark bat cave and you will understand how important light is. Our eyes consist of rods and cones, and how they work allows us to see colors and perceive objects at night. You will notice that it is harder to see colors in the dark. That is how our eyes work. Cameras and light meters work when detecting light. But what they do read they register and they interpret what it is ‘reading’.
Scientists and physicists tried to make sense of this by coming up with “scotopic lumens”. They then took it a step further and created a series of facto. These factors compare different light sources by how lights appears: scotopic versus photopic. What came out was a series of factors between 0 and 3. Some light sources have reduced effective lumens, like High Pressure Sodium. Some light sources increased by these factors, like LED. The factor associated with LED was higher than Metal Halide. It helps to understand why LED Lights are brighter than other light sources. Even though the light meter tells us something different.
8. Rebates at time of purchase
Utility companies are trying to get their customers to convert to LED. Why? It’s a matter of economics for them. Demand for electricity is growing. So once they reach capacity, they have to choices, build more capacity or reduce demand. Reducing demand is far more cost effective than increasing capacity. Utility companies offer rebates to those who buy LED. They want you to convert from Metal Halide. Every utility company runs their own rebate program. But in general, there are some consistent processes and guidelines. For the most part:
These rebates help reduce the cost and will affect the pay back of the investment. With reduced cost, the time to repay the investment goes down with addition of rebate dollars.
With Metal Halide there are no rebates. Sorry.
9. New versus Retrofit
So at this point you are thinking that converting from Metal Halide to LED is a good idea. But this is where the journey begins. What to choose, what vendor to work with, new or retrofit. Think of the LED Market as the wild west. And with every gun show there are the snake oil salesman trying to get you to buy their lotions. In the LED world, there are many lotions, misconceptions and marvelous marketing ideas. For example, well built LED Retrofits will perform as well as a new LED fixture. It doesn’t always make sense to replace the fixture, nor does it always make sense to retrofit a fixture.
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Comparison Table of LED vs Metal Halide
|Color Temperature||LEDs are available in a wide range of color temperatures from 2700K (warm yellow) to 6500K (cool blue).||Metal halide lamps generate a white light between 3000K and 5000K.|
|Color Rendering||CRI for LED is dependent on the particular light in question. That said, a very broad spectrum of CRI values is available ranging generally from 65-95.||Metal Halide are a good source of high CRI white light. It is a better light than high pressure sodium.|
|Turning On and Off||LEDs are an instant on and install off. No noticeable strike time is detectable.||Metal Halide lights have a long warm up time and can take 15-30 minutes to get to full power.|
|Dimmable||LEDs are controllable when equipped with the proper driver. Most industrial dimmers are 0-10V dimmers. Commercial consumer LEDs are triac dimmable using a regular LED compatible dimmer switch.||Metal halide lights are dimmable using electric or magnetic ballasts.|
|Directionality of Light||LEDs are directional and the light goes where pointed. Without optics, reflectors are not required unless you need a specific distribution pattern.||Metal Halide lights are omni-directional emitting light in a 360 degree pattern. To focus the light, reflectors and lenses can be used to collect the light and then direct it as needed.|
|Lumens per Watt||LEDs are very efficient with efficiencies approaching 200 lumens/watt. Not all LEDs are the same, and efficiency varies from product to product.|
Metal Halide lights average efficiency range between 70 and 100 lumens/watt. This does not include ballast draw which can add another 15% of energy consumption.
|L70 in hours||LED L70 times (years passed until lumen output reaches 70% of initial lumens) range from 30,000 to over 200,000 hours.||Metal Halide lights have a very quick L70 period, when a bulb reaches 30% of its life, it has reached its L70 mark. When a bulb is at 1/2 life, it is only producing 1/2 of its intial lumens.|
|Light Emissions||LEDs do not produce Ultra Violet or Infrared Light unless designed to do so. The light it generates is all visible light.||Metal Halide lights produce both IR and UV light.|
|Heat Emissions||LEDs produce very little heat. All LED lights do requires some sort of heat sink to reduce the heat produced by the LEDs.||Metal halide bulbs produce a tremendous amount of heat. Fixtures designed for Metal Halide must be large enough to handle the heat generated. A Metal Halide bulb turned on for a few hours is far too hot to touch.|
|Failure||LEDs fail over time by producing less light.||Metal Halide bulbs exhibit an end-of-life process called cycling. The lamp may go on and off. The bulb will fail at some point.|
|Lifespan||Industrial LEDs last between 50,000 and 100,000 hours or more. The lifespan of a LED driver is different than the LEDs themselves. It may be possible to replace the LED driver in the fixture to extend the life of the product.||Metal Halide lights have typical bulb lifespan values range from 6,000 hours to 20,000 hours. Metal Halide ballasts operate on a different life cycle with it’s own lifespan cycle.|
|Lifetime Costs||LED lighting has higher initial cost and very low lifetime costs. It pays back over time with lower energy consumption and reduced maintenance costs.||Metal halide lights have a lower initial cost but are expensive to maintain. Metal halide bulbs consume more energy than a LED Fixture and have a higher maintenance cost.|
|Maintenance Costs||There are few maintenance costs associated with LED during the lifespan. Only fixture cleaning if needed.||Metal Halide bulbs need regular re-lamping and ballast replacement. It is not uncommon to do 4-6 bulb replacements over the lifespan of a comparable LED product.|
|Shock Resistance and Impact Rating||LEDs are solid state lights which are difficult to damage. In extreme conditions, look for lights with an impact resistance rating (IKxx)||Metal halide bulbs are fragile. If broken, metal halide bulbs need special handling and disposal.|
|Temperature Conditions||Varies, but -30C to 50C is pretty common. Extreme LED fixtures are available up to 90C||Data shows -40C to ??|
|Warranty||5 to 10 years.||1-2 years.|
There you have it, 9 backed up and legitimate reasons the fight of LED vs Metal Halide is no longer a fight. LED is a clear winner in every aspect of a light. It as the perfect HID Replacement.