First and foremost, we need to understand what DLC stands for. Design Lights Consortium (DLC) can be described as an organization made up of public utility companies and regional performance efficiency agencies with a joint mandate. This collaborative organization is in the best position to certify the quality of energy-efficient lighting. They also look into and characterize the performance of lighting products such as LEDs. The organization is mandated to promote the use of good quality, energy-efficient lighting designs in all setups, especially the commercial settings.   They offer a certification, known as DLC listed Lights, for certifying the efficiency and quality of lights.

V5.1 is one of the two Solid-State Lighting Technical Requirements versions (V5.1 and V5.0, which were released in 2020). The version (V5.1) is designed to enhance the quality of high-performance, energy-efficient commercial lighting products in the market. Its other goal is to improve the controllability of the various lighting products. All this work is achieved by establishing and reporting standards and requirements for all DLC-listed products. DLC V5.1 continuously captures the advancements in lighting quality properties. These characteristics include discomfort, glare, color performance, and light distribution. It also helps realize user benefits and maximum energy savings by enhancing the control functionality of the available energy-efficient technology. 
 
The characteristics of lighting that affect productivity, performance, comfort, mood, safety, health, and wellness, among other things, are referred to as lighting quality. V5.1 adds new spectral quality and light dispersion requirements to improve the light quality of DLC-listed items. Additional energy savings are supported by the V5.1 lighting controllability criteria, promoting better light quality for people living and working in the built environment.

What is DLC 5.1 Premium?

For lamps and retrofit kits, the DLC advanced version lamps belong to the higher-performing category. Compared with the DCL standard, the DLC standard is more advanced. The advanced rating indicates that these lighting devices perform better in terms of energy efficiency and are superior to the level required by the DCL standard in terms of light quality and controllability. The DLC advanced version logo means that the lighting products must meet more stringent energy efficiency, light quality, and controllability requirements. In other words, lighting products that have obtained DLC advanced version certification have undergone more rigorous testing.

It should be noted that only lamps and retrofit kits meet the conditions for applying for certification in the "DLC advanced" category. Many people often misunderstand or sometimes overlook the qualification requirements for "DLC advanced" certification. Please note the following types of products do not meet the conditions for being classified as "DLC advanced" certification:

- Replacement bulbs
- Items whose main purpose is described as "professional use"
- Certain retrofit kits (applicable to linear styles of lamps with 2x2, 1x4, and 2x4 structures)

The indicators used in the DLC advanced version test and report for version 5.1 are as follows:

• Efficiency: More than 15 lumens per watt. This far exceeds the standard efficiency requirements. This means that DLC V5.1 advanced version is more energy-efficient than the standard version.
  
• Color temperature: All lighting products except high ceiling lights for indoor use. The color temperature range is 2200K to 6500K, and the product must have a color temperature consistent with at least one basic, flexible, or extended nominal four-step four-sided color temperature.
  
• Uncomfortable glare: Applicable to downlights. The lamp does not meet the classification standard of v5.1 advanced version.
  
• Controllability: All lighting products should have a continuous dimming function. Please note that the advanced version classification does not accept stepped dimming.
  
• Light efficiency stability: The light efficiency stability value of DLC V5.1 advanced version is not published in the QPL.

5.1 and 5.0 have what differences?

While providing better lighting conditions for individuals in specific environments, DLC also requires achieving additional energy-saving effects, which may reduce your energy expenses. The V5 plan includes a design method that helps cover all lighting quality indicators and ensures that the listed products are all high-quality lighting products. Additionally, it helps distinguish outstanding products and achieve more energy-saving effects.

a) The demand for brightness adjustment is a major issue.
Dimmable lighting helps achieve higher energy-saving effects. It also brings more comfort and control to users. All DCL products must meet the new dimming requirements. Dimming is a requirement for DLC V5.1 and V5.0. However, there are subtle differences between the two. For example, in V5.1, the new dimming policy requires that almost all products have dimming capabilities. On the QPL, most products need to have dimming functions. This requirement aims to achieve a situation where all listed products can have dimming functions, thereby improving energy-saving effects and ultimately enhancing user satisfaction. This is different from V5.0, where only retrofit kits and indoor lamps need to have continuous dimming functions.

b) Low Glare
A lower UGR (Unified Glare Rating) indicates less glare. A visually more comfortable environment is typically associated with a lower UGR value. The standard UGR value for lighting products is 19 or below.
Some indoor SSL DLC V5.1 high-end lighting products require the use of UGR indicators. Therefore, these lamps have high energy efficiency and good glare control performance. This helps to reduce or eliminate the uncomfortable glare specific to SSL V5.0.