Below is my contribution to the May issue of tED Magazine. Reprinted with permission.

More than 360 million troffers provide general lighting in commercial buildings, according to the U.S. Department of Energy (DOE). Fluorescent remains the most predominant light source. The development of LED lighting, however, has created a major retrofit opportunity.

“At a base level, retrofit kits provide a simple way to retain existing light fixtures while minimizing expenses and providing longer life than traditional lighting,” said Eric Marsh, Product Portfolio Manager, Cree, Inc. ( “The next option is a full fixture replacement, in which the fluorescent troffer and pan are changed altogether for a brand-new LED troffer.”

Switching to LED can generate high energy savings, reduced maintenance costs, instant ON at cold temperatures, and controllability. This article evaluates the major options: replacement lamps/retrofit kits and new luminaires.


Tubular LED replacement lamps, or TLEDs, offer direct replacement of fluorescent lamps in existing luminaires. The lamp incorporates LEDs, optics and heat sinking into a single ready-to-install unit. The majority are bi-pin-based T8 products designed to replace 2-ft., 4-ft. and U-bend T8 and T12 lamps. Some products are also available to replace T5 and T5HO lamps.

“TLEDs can generate energy savings in the 40 percent range when paired with a traditional fluorescent ballast and additional energy savings when paired with a dedicated LED driver,” said Jon Zelinsky, PE, Contractor Marketing Director, Philips Lighting. “Retrofit kits can drive energy savings in the 50-75 percent range.”

The DesignLights Consortium (DLC) maintains the Qualified Products List (QPL), identifying TLED products that satisfy performance criteria updated in 2016. DLC requires a minimum efficacy of at least 110 lumens/W as a bare lamp and at least 100 lumens/W as tested in a typical luminaire. (In comparison, a bare fluorescent lamp has an efficacy of about 100 lumens/W). Many utilities rely on the QPL to qualify eligibility for their rebate programs. According to rebate management firm BriteSwitch, the average rebate for a TLED is $6.84 in 2017, with rebate funding in decline as costs decline.

One indicator of TLED’s steady adoption is the Linear Fluorescent Lamp Index, which is based on sales by members of the National Electrical Manufacturers Association (NEMA). NEMA estimated that in Q32016, TLED lamps accounted for nearly 13 percent of fluorescent lamp shipments.

TLED lamps are categorized as three major types:

• UL Type A: The lamp operates on a fluorescent ballast. Pros: This “drop in” lamp provides simple installation and, if appropriately listed, does not change the safety certification of the luminaire. Cons: Lower efficacy due to ballast losses, and the TLED lamp must be compatible with the ballast, which remains a point of failure.
• UL Type B: The lamp is powered by an internal driver, which allows it to bypass the ballast. Line voltage wires to the lamp sockets. Pro: Little rewiring, as the installer removes the ballast and rewires the sockets. Con: It requires electrical modifications and proper labeling to ensure fluorescent lamps are not installed in the modified sockets.
• UL Type C: The lamp bypasses the ballast and operates with an external driver, which connects to the sockets using low-voltage wiring. Components should be packaged in a UL-classified kit. Pros: High efficacy, multilamp driver operation, greater control capabilities. Con: The most labor-intensive option.

With each option, the installer may need to replace the existing lampholders to support the heavier TLED lamp. In February 2017, the American National Standards Institute (ANSI) revised two lighting industry standards to include G6.6 lamp bases and holders. This provides a new connector system specifically designed to hold and power TLED lamps across a wide range of voltages. The base includes two internal power pins and an additional ground pin that mates to the compatible lampholder.

“If you are trying to maintain your current look in a space, are looking for a fast and easy installation, have budget restrictions, or are spot relamping in a massive building, TLED lamps are a great option,” said Alfred LaSpina, LED Product Group Marketing Manager, LEDVANCE ( “LED lamps are now being produced with optimized glass optics that mimics the light distribution and look of traditional lamps.”

Image courtesy of Philips.

Retrofit or replace?

LED troffers and panels offer a fresh alternative to retrofitting existing luminaires. Among the more than 7,300 LED troffer/grid ceiling luminaires listed in the DOE Lighting Facts database in December 2016, the majority produced comparable light output as their fluorescent counterparts, but at a higher efficacy. About one out of 10 listed products operated at an efficacy of 125 lumens/W, in fact, identifying the product as DLC Premium. That efficacy is generally lower than TLED bare lamps but at the high end of TLED efficacy when accounting for TLED light losses when operating within a luminaire. It translates to up to 70 percent energy savings compared to standard fluorescent troffers, which can be accelerated with controls.

LED luminaires are purpose-built for the light source’s unique characteristics, potentially resulting in higher-efficacy quality lighting with a modern aesthetic. However, luminaire replacement typically poses a higher cost than replacing the lamps with TLEDs.

A third option is a retrofit kit, which packages the lamp or a light engine assembly with optics and electrical components to produce a repeatable solution. By incorporating optics, retrofit kits can improve light distribution and aesthetics while expanding control options, achieving a solution close to a new luminaire. Retrofit kits offer a middle-of-the-road option in terms of cost and lighting quality.

Below are several considerations for selecting an option that is optimal for a given application.

Existing conditions. TLED lamps and retrofit kits lend themselves better to applications where the existing luminaires are relatively new and in good condition, and/or where working above the ceiling is prohibitive. New luminaires and retrofit kits lend themselves well to applications where the luminaires are older and showing wear and tear.

Number of lamps. “Troffers may have any number of lamps—one, two, three, four—so one would have to consider the number of lamps and ballasts that an owner has,” Zelinsky said. “A four-lamp and two-ballast fixture may be more expensive to replace individual components instead of putting in an LED retrofit kit or new luminaire.”

Compatibility with ballasts. “One potential disadvantage of replacing fluorescent lamps with LED lamps instead of replacing the luminaire is ballast compatibility,” LaSpina said. “Working with a lighting manufacturer that provides an extensive ballast compatibility list for their TLEDs will ensure you have lamps that work with existing ballasts.”

“Additionally, it is worthwhile to consider the age or expected remaining life of the ballast in the fixture,” Zelinsky said. “A ballast that may need to be replaced in the near term anyway would wind up adding labor costs.”

Light level and distribution. The new lighting must satisfy the application’s maintained light level requirements. Lower-output lamps and luminaires are available for spaces that are overlighted. Alternately, the space could be redesigned for fewer luminaires. In applications requiring uniformity, light level must be evenly distributed across the workplane. TLED lamps are directional (some with light emission as narrow as 105 degrees) while fluorescent lamps are omnidirectional, which may result in dark spots between installed luminaires. While energy is important, the designer should ensure at a minimum that the new lighting maintains existing lighting quality in terms of light level, uniformity and glare.

Space appearance. “A full fixture replacement is ideal for projects in which the goal is to transform the space,” said Jeff Hungarter, Senior Manager, Product Marketing, Cree, Inc. “Replacing the luminaire enhances the look of the ceiling to be modern and up to date. Other benefits include efficacy performance enhancements, improved dimming and control systems, better light quality and longer warranty.”

If the owner rules out new luminaires, Cree’s Marsh advised retrofit kits over TLED lamps. “A retrofit kit basically looks like an entirely new LED troffer in the space, providing a fresh new look,” he said. “At this point, it’s hard to think of a situation where TLED lamps make much sense.”

Lighting controls. “It’s always a good idea to make sure that you are taking the opportunity to include controls as part of the retrofit,” said Ethan Biery, LED Engineering Leader, Lutron Electronics. “Controls can significantly increase the flexibility and comfort of space lighting, and in all cases, control will increase energy savings.”

The ultimate option, he pointed out, is new dimmable luminaires with high-quality drivers, combined with an integrated intelligent lighting control system that provides robust control capabilities. The next level would be dimmable retrofit kits with compatible controls. If TLED lamps will be installed, the first step is to ensure compatibility with the existing controls, if present. He advises against pairing a UL Type A TLED retrofit with existing fluorescent dimming ballasts. In Biery’s view, TLED retrofits are ideal for applications requiring only switching and that will never require dimming.

“No matter which option is chosen, the same concerns with control of all LED fixtures apply: ensuring compatibility and good dimming performance with any control system being used,” he added. “Poor performance can result if you choose a seemingly quick, lowest-cost TLED lamp retrofit.”

Final word

“Know the goals of your customer,” LaSpina advised. “Are their main priorities energy savings, a new look for the space, or ROI options and total cost of ownership at end of life? This will help you pick the right solution for the application. If you tie it to utility rebates, it is even better for the customer.”