Lighting Technologies: T5 lamps vs. T8 lamps

As engineers, we strive to find ways of utilizing new technologies in our clients’ buildings that not only provide energy savings, but do so at a justifiable cost to the end user. Typically, our standard at Mullinax Solutions, Inc. is to push technologies that offer a 2-10 year payback, depending on the application and technology type. T5 fluorescent lamping is fairly new technology that is garnering attention in today’s energy conscious society. Below is a brief look at our experience and opinion on the T5 lamping technology.

T5 fluorescent lamps are advertised as the next step up in terms of energy savings when compared to the standard T8 fluorescent lamp. Standard T5 lamps are 28 watts and standard T8 lamps are 32 watts. On a per lamp basis, it’s a 12.5% energy savings. From that perspective alone, it sounds like an attractive alternative. However, there are a number of disadvantages to the T5 technology. T5 lamps are not the same length as the 48” T8 lamp. Instead, they are 2” shorter, at 46”. Building owners or facility managers who desire to use them will not be able to easily retrofit existing T8 fluorescent fixtures with T5 lamps. There are retrofit lighting trays available that close the 2” gap and allow for the usage of T5 lamps in T8 fixtures, but that is just one more element that increases the retrofit application costs. Speaking of costs, a standard T8 lamp will run you about $2 a lamp where a standard T5 lamp is about $8-10. That’s a fairly large cost increase to only net 4 watt savings on each lamp. In 2006, we fell victim to the promises of the T5 technology. While working on the electrical design for a new elementary school, a lighting representative sold the idea of T5 lighting fixtures to us, which at the time was a newer technology. Their sales brochures and limited data lead us to specify their new fixtures and lamps. After design documents were completed, much like the majority of new construction projects, the time for value engineering came. One of the first items on the list was the use of parabolic T8 fixtures instead of the T5 lighting fixtures. In considering the ramifications of this change, we decided to put the savings promised by the T5 fixtures to the test. An energy model was constructed and we compared the yearly savings of utilizing T5 fixtures vs. the standard equivalent of T8 fixtures. Our results netted the owner a payback on the initial cost of approximately 13 years. That figure in itself did not take into account any of the lamp replacement or maintenance which would also have been more expensive than that of the T8 lamped fixtures. Ultimately, we ended up changing all of the T5 fixtures to standard T8 fixtures.

The T5 lamping technology in itself, is not impractical by any means and it is not our intention to present it in this light. Nowadays, the minor energy savings does not justify the high initial costs, in our opinion. Furthermore, there are newer technologies today that further negate the advantages of T5 lamps, such as 28 watt T8 lamps, high lumen output T8 lamps, and LED tube lights. The majority of these alternatives stack up well when compared to T5 lamps, and would likely yield shorter paybacks to the end user. All negative criticism aside, there are certain applications where T5 lamps make sense. T5 high output lamps (at 54 watts each) are a great alternative for certain high ceiling applications (gymnasiums, retail, high ceiling coves, or industrial applications).

In conclusion, we believe that building owners and designers looking for energy savings in fluorescent applications should first consider the newer 28 watt T8 lamps, more efficient ballasts, and reliable lighting control schemes. T5 lamping and fixtures may be a modern option, but in our experience, there are more cost effective solutions in today’s market.

Author: Jeffrey Morgan, P.E. – Mullinax Solutions Project Manager

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