What Is the Difference Between Edge-lit and Back-lit LED Panels?

Ceiling lights called LED panels make a great contribution to energy saving, especially in commercial areas. For this reason, fluorescent ceiling lamps are rapidly being converted to LEDs today.

There are two different design approaches for LED panels; edge-lit where the light source LEDs are placed at the edges, and back-lit where the LEDs are placed on the base behind the light emitting surface. What are the differences between edge-lit and back-lit?

In the model called edge-lit, LED chips are placed on the inner edges of the luminaire. The light coming from the sides is directed downwards with the help of the diffuser in the middle. Directing the light in this way and transporting it out of the luminaire causes some losses in the light.

In back-lit panels, the LED chips are placed at the base of the luminaire. The light is thrown out of the luminaire by passing through a softener diffuser in the direction of its propagation. The diffuser used in the back-lit panels transfers the light out with higher efficiency. Therefore, it can be said that back-lit panels have higher light output than edge-lit panels with the same power consumption. In other words, the back-lit has higher luminous efficiency and saves more energy.

To explain with a simple example based on the current state of technology; back-lit LED panels have a luminous efficiency of 100-150 lm/W, while edge-lit LED panels have a luminous efficiency of 70-100 lm/W.

Figure 1. Light distribution in edge-lit and back-lit LED panels

Edge-lit panels are generally cheaper than back-lit panels. Although edge-lit panels seem to be cheaper in terms of purchasing cost, it can be said that lower system costs will emerge with back-lit panels when energy savings (operating cost) are added to it.

The advantage of edge-lit panels is that they are thinner. Thin body makes installation easy, application more flexible.