How To Evaluate Cost-Effectiveness of LED T8 Lamp Retrofits for Troffers

Life is more complicated these days for facility managers charged with, among many other tasks, maintaining an effective building lighting system for the occupants while trying to reduce, or at least stabilize, energy costs.

While there is a wide range of lighting tasks and types of light fixtures in commercial and institutional buildings, by far the most common is the general space lighting provided by fluorescent tubes mounted in troffers. In 2016, the U.S. Department of Energy (USDOE) estimated there were over 300 million troffers installed in the country.

With such a large installed base, it is no wonder LED lamp and fixture manufacturers have focused on LED alternatives.

This is both good and not so good news for facility managers. At first glance, retrofitting with LED equipment holds out the promise of significant energy savings and lower long term maintenance costs due to long rated lamp life.

However, once facilities staff researches the many LED options for retrofitting existing fluorescent fixtures, each with it’s own set of costs and installation requirements, and, compares the LED option to a fluorescent upgrade, the path to lower energy and maintenance costs gets decidedly more challenging.

In this post we will show facility managers how to get an initial “first look” on the potential of a cost-effective LED retrofit.

Review of LED T8 Lamp System Options

LED T8 lamps typically are available in these three set-ups:

  • Ballast Compatible – direct replacement, requires instant or programmed start ballasts
  • Ballast Bypass with Internal Driver – re-wire line voltage directly to the sockets
  • Ballast Bypass with External Driver – replace existing ballast with LED driver

Generally, when considering both material and labor for installation, the cost of the Ballast Compatible option is lowest. The Ballast Bypass / Internal Driver option has the next lowest cost and the Ballast Bypass / External driver will be the most expensive.

Of the three LED T8 options, the Ballast Bypass / External Driver combination provides the highest efficiency and longest lamp life compared to the other options. While this may be true, it does not mean the other two options should be dismissed as viable candidates for the retrofit. Much depends on the existing fluorescent troffer installation and, of course, the budget.

Lamp / Ballast Combinations Typical of Existing Fluorescent Installations

Facility managers should consider the benefits of an LED retrofit based the existing fluorescent system. Here are four likely installations:

(1) T12 fluorescent lamps and rapid-start ballast, either magnetic or electronic

(2) T8 fluorescent lamps and rapid-start ballast, either magnetic or electronic

(3) T8 fluorescent lamps and older, standard-efficiency, instant-start electronic ballast

(4) T8 fluorescent lamps and newer, high-efficiency, instant-start (or programmed start) electronic ballast

When LED retrofits are being considered, each of these configurations will present different opportunities.

Fluorescent Lamp / Ballast Combinations (1) and (2)

There is a much greater chance for an LED retrofit to provide an attractive return on investment when the existing installed lamp / ballast system is either T12 or T8 lamps using magnetic or electronic rapid start ballasts. These systems are inefficient and generally have higher maintenance costs. LED retrofit costs will be higher, because of the requirement for either a new instant start / program start ballast or an external driver and possibly new sockets, but the long term cost-effectiveness will likely be excellent.

Fluorescent Lamp / Ballast Combination (3)

The T8 lamp and older instant start ballast combination can be a good candidate for LED because the relatively low overall system efficiency of the existing system allows room for improvement.  One of the LED T8 retrofit options is designed to use the existing instant start ballast and usually the same sockets which means a simple and lower cost installation.

This retrofit does not require an electrician. It is simply plug-n-play.

However, the energy savings may be compromised by the inefficiency of the older ballast. In addition, there is the possibility that the ballast may be toward end of life and need to be replaced in the near future – another cost to consider.

The main benefit of this type of LED retrofit is that it minimizes up front retrofit costs. Overall performance will be marginally lower than a retrofit that uses LED T8 lamps designed to operate off an external driver – bypassing the existing fluorescent ballast.

Fluorescent Lamp / Ballast Combination (4)

If the existing troffers utilize newer T8 lamps and a high efficiency instant start ballast system, this set-up will not generally present a strong opportunity for an LED retrofit because the fluorescent system is already energy efficient. The easiest, lowest cost upgrade to get additional efficiency is simply to do a direct replacement with new 28 watt T8 fluorescent lamps replacing the existing 32 watt lamps. Instant energy savings with very similar illumination performance will be the result.

The 28 watt fluorescent replacement will also likely mean lamps with a 35,000 to 40,000 hour rated life which will lessen the advantage of lower maintenance costs (fewer lamp changes) often promoted as one of the major benefits of LED.

CALiPER Study Provides Additional Analysis of LED T8 Lamp Retrofit Cost-Effectiveness

A recent USDOE LED linear T8 cost-effectiveness study, published through the CALiPER program (Commercially Available LED Product Evaluation and Reporting), goes into significant detail about the process of analyzing an LED retrofit for existing troffers. This report is recommended reading for any facility manager considering an LED T8 retrofit.

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Dave Burtner

Dave has been active in the lighting industry since 1994. Formerly a member of the Illuminating Engineering Society of North America and certified by the National Council On Qualifications for Lighting Professionals, Dave now writes blog posts, lighting tips and provides lighting product assistance for the Topbulb website.

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