Although we evaluate an existing lighting system based on pupil lumens, we still compare photopic lumens and lumen maintenance to determine the best solution. For example, the photo (on the left) is of a high school parking lot with a 250W HPS bulb (right side) next to a 54W LED bulb (left side) at 6500K color.
Which one looks brighter, and is easier to see true color? The LED bulb has a higher scotopic sensitivity, and thereby the perception of brightness of the area is influenced by rods in the eyes and appears brighter. Although the 250W HPS bulb measures higher photopic lumens, 12,850 vs. 6,480, it has less overall pupil lumens, 8,851 vs. 11, 430. Additionally, only 29% of the energy used in a HPS lamp produces light.
Reasons To Consider LED Replacement Bulbs vs. T8 Fluorescent Bulbs
Here are 6 solid, factual based reasons why you should consider DIRECT Replacement LED Bulbs over T8....
- LED Replacement Bulbs are 30-55% More Efficient
You get more light from a LED replacement bulb and they use less wattage. Our LED replacement bulbs only use 15 to 22 watts vs 28-32 watts with T8 making the LED a 30-55% more efficient light source. The LED replacement bulb emits light at a 120 degree pattern vs the 360 degree pattern given off by T8 fluorescent bulbs. In this case, only 30% of the light given off by the t8 fluorescent is actually hitting the intended target.
- LED Transfer Light vs. Heat
LED lamps use their energy to produce light. Most lighting sources including fluorescent use heat to generate light which is why traditional incandescent, metal halide and fluorescent are losing favor with property owners.
- LED Still Give Off Light At End-Of-Life
A fluorescent bulb at the end of its life is very simple to spot, because it is flickering, has burnt ends or not on. A T8 bulb is considered end-of-life at 60% of its light output, which equates to roughly 14,400 hours. LED replacement bulbs on the other hand, calculate the end of life at 70% which is approximately 50,000 hours. At which the LED lamp is still on but the amount of light output starts to deteriorate. In order to keep up with LED, you will have to replace the T8 bulbs 3.5 times.
- LED Replacement Bulbs Have No Mercury
One of the most important differences lies in the fact that there is no Mercury or Glass Content with LED lighting. In most states over 10 Million lamps are disposed of in landfills each year. Those 10 Million lamps hold roughly 400 lbs of toxic Mercury waste that gets deposited each year. Estimates are that only 2 out of 10 bulbs are effectively recycled.
- LED Lamps Do Not Give Off UV
LED replacement lamps do not emit any light in the non-visible light spectrum (UV). UV/IR light causes colors to fade in fabrics and signage, while also being the leading cause for eye strain and eye fatigue. Fluorescent T8 bulbs emit UV/IR light.
- Reduced Maintenance Cost
New Led lighting products are far superior to technology that is even five years old. We used new LED lamps and fixtures in one facility that has a 50,000 hour life or 12 years at the level of usage in this facility. Each year, the owner spent $2500-$3500 per year to replace worn out ballasts and change burned out light bulbs. Since they upgraded to LED lighting that has a 50,000+ hour life, they will not need to spend that money each year. By upgrading the lamps to LED’s, they eliminated the need for routine annual maintenance which saves $2500-$3500 a year or $30,000 over 12 years. That is an expense they won't have to pay out. Which becomes money in their pocket.
Intel Tests Scotopic vs Photopic Vision
An experiment at Intel Corporation proved the scotopic-photopic theory. Described in Dr. Sam Berman’s article “The Coming Revolution in Lighting Practice,” Intel facilities staff observed during the study that one could see better under the scotopically rich lighting, and that this lighting was actually perceived as brighter even though a traditional light meter would indicate the opposite.
Intel realized they would achieve larger energy savings by reducing the number of lamps needed while at the same time improving overall lighting perception and effectiveness. In the campus’s eight buildings, scotopically enhanced lamps have yielded annual lighting energy savings of slightly larger than eight million kilowatt hours.
Footcandle Readings No Longer Enough
Light meters see light as photopic, however with the color rendering of todays newer lighting technology that is not always enough. That is how we can have a lower FC reading on a meter and yet to the human eye, the area is significantly brighter. The human eye is a far better "light meter" than any little gadget.
We Have Seen "The Light"
We have witnessed this first hand on one of our projects. We replaced 1000W metal halide fixtures with 240Watt LED fixtures. The results? The light meter said that there was less light. The human eye said not only is there more light, but the colors look more accurate as well.
How Does Scotopic vs Photopic Relate to Energy Efficiency?
This topic is relevant to energy efficiency because when you are re-designing a facility for new lighting, you may be able to reduce the wattage of your fixtures even further. If you understand the relationship between Scotopic and Photopic, you may be able to reduce your energy costs even further.