Why is it you can replace some lights with more ‘advertised’ lumens with a LED light with less lumens. Here are 4 reasons why you can use less LED lumens to replace traditional HID lights
1. You need less lumens when you have Focused Directional Lumens
LED light is directional. Conventional light sources are omni-directional. They require reflectors to gather the light and focus it. Any reflection that is over 1 bounce effectively loses the effect of the lumen. It has been proven that you can lose up to 30% of the effective lumens in this process.
2. Quality of Lumens – you need less quantity when you have better quality
This is related to Color Rendering Index, or CRI. The best explanation is a simple test. Compare LED Light to High Pressure Sodium. It is not uncommon to have customers tell you that 20,000 lumens of LED appear brighter than 60,000 lumens of HPS. The basic truth is you need less quantity when you have higher quality. CRI is a scale between 0 and 100. It measures the quality of an artificial light source compared to a high quality light source, like the sun. Read more about CRI here.
3. Photopic and Scotopic Lumens
This has to do with how a camera perceives lumens and how humans perceive lumens. Photopic lumens are lumens detected by a light meter. Light meters register photopic lumens. Scotopic lumens are lumens detected by the human eye. LED produces light within our range of visible spectrum’s. The light created by LED is light we use. It is rare to see a LED light produce IP or UV spectrum. These wavelengths are invisible to people, so they have no value to us from a vision perspective.
Scotopic lumens uses a factor to adjust the photopic value of light. It gives a truer representation of how useful the lumens are. The factor, developed by scientists, is an attempt to level the playing field. The factor’s used to adjust the effective value of the lumen. This factor may move the photopic lumen up or down. HPS lights have a factor that reduces the effective scotopic lumen amount. LED has a factor > 1.7, which means the lumens it is producing is far more effective to us. Less photopic LED lumens are needed, where as more HPS lumens are needed to effectively light up an area.
4. Lumen Degradation
It is not uncommon for HID bulbs to have lost up to 50% of its initial lumens after only 5000 hours of life. Yet these bulbs are rated for 20000 hours. That means the customer is using a bulb that is performing poorly for 15000 hours of its life. As well, as lumens degrade, so does the quality of the light (CRI). And so the “effective lumens” of the light is dropping quickly.
We have been very successful replacing 400W Metal Halide bulbs with our 100W LED to HID Replacement Kit. The comments we here back is the light is brighter and the area is brighter. It currently produces 15,500 lumens.
Another example is 120W LED Bay Fixture producing 18,000 lumens. This is designed to replace upwards of 400W metal halide. If you have a bay fixture with a 400W Metal Halide bulb, this light is going to be a dramatic improvement over what you have.
A HID fixture is a lighting device that consists of a fixture, a HID bulb, a ballast, reflectors and a mount. HID is an acronym for High Intensity Discharge, and applies to a family of high lumen bulbs. Mercury Vapor, Metal Halide. Ceramics, Sodium Vapor and Xenon based bulbs are all considered to be HID bulbs. All HID bulbs need a ballast that converts AC line power into energy used to power the HID bulb.
The bulbs are omni-directional in nature, and they create light in all directions. To focus HID lights, adding reflectors and lenses to the fixture to direct the light where its needed. HID bulbs are very bright, but required a long strike time to produce greatest levels of light. If you switch off a fixture, the amount of time it takes to re-cycle the fixture is considerable. The two most common HID bulbs are metal halide bulbs and sodium vapor bulbs. Both bulbs are distinctive. Sodium bulbs are orange in color, metal halide are whiter.
Applications for HID Fixtures
HID fixtures are for high lumen applications. Indoor applications like gymnasiums, warehouses, bay fixtures, shop lighting, recessed lights and factory lights. Outdoor applications include parking lots, stadiums, street lights and area lights. HID bulbs come in a variety of wattages for different applications.
Large fixtures with high wattage bulbs use 1000W, 1500W and 2000W HID bulbs.
Smaller bulbs used in bay fixtures and parking lit lights use 250W and 400W bulbs.
Smaller wall mounted fixtures with less lighting requirements, 100W and 150W bulbs.
Life of a HID bulb
HID bulbs have different lifespans, between 12,00 hours to 20,000 hours. During this lifespan, light out degrades with the age of the bulb. It is not uncommon that after 1/2 life of the bulb, the HID bulb has lost over 50% of its effective lumens.
A bulb that has used 80% of its life is only producing 20% of its initial lumens. Thus, it is not uncommon to replace bulbs well before complete End of Life.
A phenomenon associated with HID lamp wear and aging is discoloration of the light. In whiter based HID bulbs, this means the shift is to a blue or violet shade.
Converting HID Fixtures over to LED
So why are users of HID Fixtures converting to LED? When LED was in its infancy 11 years ago, LED barely produced enough light to replace HID bulbs. LED was inefficient, and expensive.
LEDs have matured, and mass production has brought down the cost of the product. LED options now produce enough lumens to compete against their HID counterparts. LED offer several advantages over the HID fixtures.
LED is energy efficient, using 25% of the energy that a HID bulb uses to produce the same amount of lumens.
LED’s life spans are longer than HID bulbs. A 20,000 hour HID bulb has a L50 of 10,000 hours. Some LED fixtures currently have a L70 exceeding 100,000 hours.
The purity of LED light is better than HID lighting. Some metal halide bulbs have a high Color Rendering Index (CRI), but most LED products have a high CRI. Sodium Vapor bulbs have a horrible CRI.
Replacing HID fixtures or Retrofitting HID Fixtures
There are 2 options that are available converting HID to LED: replace or retrofit. Replacement means removing the fixture and a installing a new LED fixture. Retrofit is removing HID components from the fixture and replacing with LED components. Both options have pros and cons. Which one to use depends on circumstances unique to the fixture and installation.
LED Kits for HID Fixtures are a series of 11 kits designed to replace all HID bulbs ranging from 150W to 1500W. HID Retrofit Kits are a certified retrofit solution. As part of the installation process, remove the reflector as it is not required. Expect energy savings around 75% over their HID counterparts. Life span should exceed 10+ years under normal operating conditions.
We all know that converting from Metal Halide (HID) 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 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:
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:
Utilities offer both prescriptive and custom rebate options. A prescriptive rebate specifies which LED fixtures can replace a metal halide fixture. A custom rebate is for those exceptions not covered by prescriptive conditions
Most LED products need to be DesignLights Consortium Qualified. This is a symbol of efficiency and performance. It is the equivalence of Energy Star for consumer products. It tells the customer the lights passed a specific lighting standard.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Varies, but -30C to 50C is pretty common. Extreme LED fixtures are available up to 90C
Data shows -40C to ??
5 to 10 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.
How many LED watts does it take to replace a 1000 watt metal halide?
It’s a simple question that requires a complex answer. You can’t base your decision off of watts. Instead, you need to base your decision based on the amount of lumens you need. Once you get the lumens dialed in, find a fixture that produces that lumen amount.What is a lumen?
In simple terms, it’s a unit or measurement of light. For light fixtures, we calculate the total lumen output. That tells us how bright the fixture will be.
Does this matter? A lot more than you may think. It’s what matters when replacing old light systems.
When replacing an existing fixture, determine the lumen output per fixture. Metal halide fixtures, with fresh bulbs, output at 100,000 (initial) lumens per 1000 watt bulb. You do not need to replace 1000W Metal Halide with 1000W LED. Instead, you need to find the equal replacement for the 100,000 lumens. You can forget about replacing watts and focus on replacing lumens.
In the above example, 1000W producing 100,000 lumens, the efficiency is 100 lumens per watt. In the world of today’s lighting, this is OK, but not great. You need to be aware of some other factors going on.
100,000 lumens may seem bright. It is. Metal Halide bulbs have high initial output. They suffer from fast lumen depreciation. It is common for a metal halide bulb to have lost 50% of it’s lumens at half-life.
L70 is a term for the number of hours before a bulb is performing at 70% of initial lumen output. For metal halide, 70% of its lumen output calculates to about 5000 hours. So, while the specs say 100,000 lumens, it won’t be 100,000 lumens for long. LED maintains its lumens much better.You will notice L70 times for LEDs are 50,000 and 100,000 hours, not 5,000 hours like it is for metal halide bulbs.
Loss of Light due to Reflection
LED light is directional. HID light sources are omni-directional and need reflectors to focus light. Any reflected lumen that bounces more than once is a lost lumen. Studies show that you can lose up to 30% of the effective lumens in the reflective process.
If a metal halide bulb has 100,000 initial lumens, the loss associated to reflected lumen bounce is around 30,000 lumens.
Quality of Lumens
This relates to Color Rendering Index, or CRI. Its a measurement of quality, not quantity. The higher the quality, the less quantity you need. Often, customers tell us that 20,000 LED lumens appear brighter than 40,000 HID lumens.
The basic truth is you need less quantity when you have higher quality.
Photopic vs Scotopic Lumens
This has to do with how a camera perceives lumens versus how humans perceive lumens. Photopic lumens is light detected by a light meter or camera. Scotopic lumens are lumens detected by the human eye. LED produces visible scotopic light. It is rare to see a LED light produce IR or UV invisible spectrums. These wavelengths are invisible to people, so they have no value to us from a vision perspective. Light meters detect invisible spectrums, giving a false perception of brightness.
The science of scotopic lumens includes a factor used to adjust the photopic value to give a true representation of the lumens quality. This factor is the S/P ratio. The S/P ratio attempts to level lumen quality between light sources. The factor adjusts the effective value of lumens, up or down, from the photopic lumens.
Assume you have an 40,000 lumen high-pressure sodium (HPS) fixture and a 12,000 lumen LED fixture. Is the LED fixture capable of replacing the HPS fixture? Based on this data, you may think that the LED will only deliver 25% of the light provided by the HPS light.
Consider the following S/P ratios:
LED S/P ratio = 2.0
HPS S/P ratio = 0.5
The scotopic lumens provided by each light source would be the following:
LED scotopic lumens = 12,000 lm x 2.0 = 24,000 lm
HPS scotopic lumens = 40,000 lm x 0.5 = 20,000 lm
The LED would appear brighter even though it is 28,000 less lumens.
Light sources with higher scotopic factors need less lumens for us to perceive and detect the light.
Summary: How to convert 1000W Metal Halide to LED
The basic takeaway from this is you need far fewer LED lumens than metal halide or HPS lumens.
Metal Halide bulbs are very bright out of the box, but degrade.
LED light is directional. LED light goes where its pointed. It is very efficient.
LED light is high quality light. You need less quantity.
So how much LED Lumens do you need?
Only a photometric can tell you exactly how much you need. But in our 10+ years of selling LED lighting, our general rule of thumb is:
Indoors: 45,000 to 65,000 lumens (depends on application and mounting height)
Outdoors: 40,000 to 75,000 lumens (depends on application and mounting height)
By searching for LED to replace 1000W HID you can find LEDs that are more efficient than 100 lumens/watt. Lumen efficiency for LED is getting closer to 200 lm/watts. This will allow a cut of watts used by 75% or more.
But What Does “replacing” Consist of?
Replacing can consist of two things: retrofitting or full replacement. The difference is simple, a retrofit kit is like replacing the light source in the fixture. While full replacement includes replacing the existing light source and fixture. To be able to decide which one is best for you will depend on your facilities’ situation. If your existing fixture shell is in good condition, retrofitting will work. If they are old, outdated and need replacing, a full replacement is the best option.
Are the LEDs in a retrofit kit as good as a LED fixture?
Yes. Retrofit/hid replacements perform or last as long as a new fixture. Retrofits don’t always make sense. But they do if you have a significant investment in your fixture or the look of your fixture. Our retrofit kits have 10 year warranties. They have been installed inside sealed fixtures in hot locations, like Arizona, Nevada, California and even in the Middle East.
It is possible to replace a metal halide fixture with LED technology. It can be as simple as retrofitting or replacing your existing fixtures.
An investment in LED will pay back in many ways. This includes lower energy usage, lower maintenance costs and higher quality of light produced.
This blog post is our second to one of our most popular ones, “How Many Watts does it take to replace 1000W Metal Halide”. Many of the concepts are the same but there are some differences between 400W and 1000W Metal Halide. One of the most common questions we get asked is
“How many LED watts does it take to replace a 400 watt metal halide bulb?” “I just talked to another LED company and they said to use their 150W LED Fixture. How much is your 150W LED Fixture?” “I’m looking to convert my fixtures over to LED High Bay Lights and what wattage should I get?”
This approach is fraught with error. The amount of watts a LED fixture consumes does not guide replacing an existing Metal Halide or HPS light. Let us explain.
How many LED Watts does it take to replace a 400 watt metal halide?
The best advice we can give anyone is never buy a LED product based on watts. Buy it based on lumens and then figure out how little watts you can use to make those lumens.
What is a lumen?
In simple terms, it’s a measurement of light that defines how much light a certain fixture or bulb produces. It is the light you are replacing. Fixtures produce lumens and consume watts. And all the fixtures lumens combined provide a foot candle measurement. When we do a photometric calculation, we use the data associated with that fixture or bulb. We then insert it into photometric software, and calculate the foot candles for the area. In real terms, a light meter will give you a foot candle reading at the place you are standing. Move close to a light source, the foot candles will rise. Move away, it will fall. The foot candle reading between 2 fixtures is the collective lumen output. These 2 fixtures distributed to that point where you are standing.
Why does this matter? A lot more than you may think. Because it’s what matters when replacing old systems with new lighting technology.
To replace an existing fixture (or entire system), you need the lumen output per fixture. Let’s say your metal halide fixtures produce 32,000 lumens per 400 watt bulb. So instead of thinking, “I need 400 Watt LED to replace 400 Watt Metal Halide,” you need to be thinking
“I need an LED that can replace 32,000 lumens.”
Take this example of 32,000 lumens for a 400 Watt metal halide. That means its outputting 80 lumens per watt. In the world of lighting, this isn’t that efficient, with LEDs approaching 200 lumens per watt. But, there are some other factors going on here that you need to be aware.
Understanding Initial lumens and L70
32,000 lumens seems bright. Metal Halide Bulbs have high initial output because they suffer from rapid lumen depreciation. It is not uncommon for a metal halide bulb to lost 50% of it’s lumens at half life. Full life for a metal halide bulb is 15,000 hours. That means at 7500 hours of use, it has lost half (or 16,000) of its lumens.
L70 is a term the number of hours before a bulb is performing at 70% of initial lumen output. For metal halide, that calculates to 5,000 hours of use.
You will notice L70 times for LED is in terms of 50,000 and 100,000 hours, not 5,000 hours like Metal Halide bulbs.
Loss of Light due to Reflection
LED light is directional, that means all its light shines where pointed. It does not need a reflector to collect it and deliver it to where its needed. Conventional light sources are omni-directional. They need reflectors to gather the light and focus it where needed. Any reflection of a lumen that is over 1 bounce in the reflector is a loss of that lumen. You can lose up to 30% of the effective lumens in this reflective process.
If a Metal Halide bulb has 32,000 initial lumens, the loss accounted to reflected lumens drops the lumen output to around 20,000 lumens.
Quality of Lumens – CRI
Color Rendering Index, or CRI, is the best way to compare the quality of light sources. The higher the quality of light, the less quantity you need. It is common for customers to report that 20,000 lumens of LED appears brighter than 60,000 lumens of other light sources, like HPS.
The basic truth is you need less quantity when you have higher quality.
Photopic vs Scotopic Lumens – How we perceive light versus how a light meter perceive light.
Photopic lumens are lumens detected by a device, like a camera or a light meter. It picks up all sources of light that we cannot see, like UV and IR. Scotopic lumens are lumens detected by the human eye. Its how we as people perceive light.
LED produces light within these spectrum’s, which means the light perceived by LED is light that we use. It is rare to see a LED light produce IR or UV spectrum’s. These wavelengths are invisible to people, so they have no value to us from a vision perspective. It is common to stand under one LED and one traditional light sources. First read the fc measurement with the light meter of both light sources. Then ask individuals standing near by what light source they think looks brighter. And have the one that looks brighter contradict what the light meter tells us.
We perceive light sources and brightness different, in some cases, than light meters.
Summary: Converting from 400W Metal Halide to LED
The basic takeaway from all of this is you need far less LED lumens than metal halide or HPS lumens.
Metal Halide bulbs are very bright out of the box, but not so much even after only 6 months of use.
LED light is directional. The light goes where needed. No loss due to reflection.
LED light is high quality light. You need less quantity when you have higher quality.
So how much LED Lumens do you need?
Only a photometric can tell you exactly how much you need. But over almost 10+ years of selling LED lighting, our general rule of thumb is:
Indoors: 15,000 to 25,000 lumens (depends on application and mounting height). You would find these lights in a warehouse, factory, gymnasium, auditorium or swimming pool.
Outdoors: 14,000 to 20,000 lumens (depends on application and mounting height)
By searching for a LED to a 400 Watt Metal Halide you can find fixtures that output at over 100+ lumens / watt. If you choose a reputable company with high quality product, you can reach higher than a 150 lumens / watt output. This allows you to cut your wattage usage per fixture by 2-3 and sometimes 4 times. This will save a lot of energy when you replace many fixtures.
What are my “Replacement Options”?
Replacing can consist of two things: retrofitting or replacement. The difference is simple. A retrofit kit is like replacing the light source (bulb and ballast) in the fixture. But, full replacement includes replacing the entire fixture including bulb and ballast. Which is best for you? That depends on your facility, fixtures, needs, and priorities. If your existing fixture shell is good to use and not outdated or falling apart, a retrofit kit will work well. If they are old, outdated, leaking or need replacing: a full replacement is the best option.
Are the LEDs in a retrofit kit as good as a LED fixture?
Yes. Despite of what you heard, there is no reason to think or believe that a retrofit conversion kit won’t perform or last as long as a new LED fixture. Retrofits don’t always make sense, but they do if you have a significant investment in your fixture or the look of your fixture. Our retrofit kits have a 10 year warranty. They are in closed sealed fixtures in hot locations like Arizona, Nevada and even in the Middle East.
Keep in mind that retrofitting is usually cheaper. This is because it’s easier to do and not as material intensive as a full replacement. So if you can retrofit, go with that over a full replacement!
It is possible to replace a metal halide fixture, that of any wattage (30 on up to 1000+), with LED technology. It can be as simple as retrofitting your existing fixtures or more work intensive to replace.
It may seem difficult and expensive but the benefits far surpass the cons when upgrading to LED. An investment in LED will provide payback in many ways: less energy usage and the higher quality of light produced.
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.
1. 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.
2. 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.
Initial Lumens: how many lumens will the fixture produce brand new
L70 Lumens: how many hours will it take before the fixture produces 70% of the initial lumen value
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.
3. 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.
4. Putting it all together – how to determine the best LED fixture to consume the least amount of energy.
So lets say you are in the market to replace your existing lighting. Here are the steps to follow.
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)
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.
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.
5. 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.