Don’t believe everything that spec sheets say. Flat panels are made up of several layers of different materials. The LED’s are mounted in the frame and face the light guide plate (LGP) which is the 3rd part from the left. This is where the magic happens and the light spreads evenly across.
Next is the diffuser we see. The LGP can be made of several materials. The BEST material is PMMA, which is an acrylic. It costs several dollars more ($2-$4) than the cheaper LGP but never turns yellow.
The lowest cost material is PS or polystyrene. This can turn yellow over 8,000-10,000 hours of operation. Another material referred to as MS or methylmethacrylate styrene is widely used as LGP and is lower cost but can turn yellow after several years of 24/7 operation. Even though the LED’s have little to no UV, when in close contact with LED’s, yellowing of the LGP can occur. The change will be gradual, but what looks like 4000K today may look like 3000K 5 years from now, and the color change is usually seen towards the center of the fixture.
During our evaluation we also found that units flicker. This is not noticeable to the naked eye but will be revealed by looking through a cell phone camera. This can be a problem for people who are sensitive to it. Flicker-free drivers usually cost about $1.60 or so more (to the manufacturer) than the non-flicker-free type.
When you purchase the lowest cost panel you are likely getting either a PS or hopefully at least MS which will last a bit longer (but you really won’t know until it’s too late).
What we are seeing from many factories is a 5 year warranty with a limit of 8-12 hours of operation per day. Many manufacturers do not want to offer a 5 year warranty at 24/7.
Our panels are PMMA and we DO offer a 5 year 24/7 warranty.
In addition to the above, there are many differences in performance. Our panels are 130 Lumens per Watt but some others are as low as 85 LpW. Many panels put out too much light – 40W seems to be very popular.
A 40W 100LpW is 4000 Lumens. This is too much light for a 2×2 in many cases. Our 25W 130 LpW is 3250 Lumens and is suitable for most applications.
If the goal is saving energy, which saves money, then the lower cost of the less efficient panel is quickly washed out by higher energy costs.
The point is, you get what you pay for.