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 T5,T8 Picture2” 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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17 Responses

  1. Hey Jeff. Looks like you all could be on to some helpful things.Look forward to more. Thanks Peter MillValley Construction

  2. Couldn’t have said it better myself. Thank You for the great post. I have meant to write a similar story on my blog. Looks like you got there first. Cheers.

  3. Now the price of the T5 tube has dropped a lot. We can buy it with $5 – 6 each.

  4. Thanks a lot, been enlightened by your article. Much apreciated.

  5. Don’t forget to account for the total system wattage, which includes the ballast. You can’t just compare the 32W to 28W lamp rating alone and be done. The real power consumption is driven by the ballast and lamp combination. Keep in mind that T5’s require a program start ballast, which typically draws more power than an instant start ballast. Depending on the application, you may be able to use a T8 with an instant start ballast, and be much more efficient, but not always. With more occupancy sensors being used, program starts are the way to go regardless of lamp selection.

    Especially when dealing with classrooms (in my experience), the T5 rarely beats the T8 in terms of system lumens/watt, lamp life, initial cost, or re-lamping costs.

  6. you forget to mention the power consumption of the the T8 magnetic ballast. a 36watt T8 would actually consume more like 54watts and not 36 watts.

    • Although T-8s in the newest of technologies use electronic ballasts, not magnetic ones. All of the retro-fit projects we do, are eliminating the use of the old and heavy magnetic ballast and using the electric ones with t-8 lamps.

      • I have a building where im thinking of changing to T-8 technology, but need help in finding a company to retofit and design it.appreciate the help.

    • Well said. A T8 with an analog ballast loses approximately 50 % of its electricity, meaning a 32 W T8 with an analog ballast uses +/- 50 Watts of electricity, whereas your 28W T5 will use less than 30 Watts.

      T8s with electronic ballasts can be a great option, but haven’t experienced them personally.

    • Who has a T8 magnetic ballast. I think you are confusing it with T12

    • Whose using t8 magnectic?? We use t8 electronic ballasts. Me?? I’m a t8 fan . I hate t5 power consumption and I hate initial cost and 4 times the maintenence cost

  7. how many tubes can be lit by 1 ballast? still just the 1?

  8. Reset Electronics has the perfect UL and ULC rated solution to convert T12 and T8 fixtures with no construction required throughout North America at a fraction of the costs mentioned above. Check us out at http://www.ecopowercanada.com and/or call us from anywhere in Canada or the U.S. at 613-596-5544 or toll free at 1-888-758-7889, ext 203. Brighten up and save with T5 lighting!

  9. Expert engineer. I found many useful knowledge here. Thank for the post.

  10. We have 32 – 3 lamp t8 fixtures. it is too much light and we removed one of the lamps from each fixture. Is there a downside to doing this in terms of lamp life or otherwise?

  11. Well written . Thank you. Have to agree , I love t8 cost t8 efficiency and t8 maintenence and bulb cost. T5 just plain uses to much power and bulb replacement requires a loan. Lol and I love that t8 you can burn 1 or 2 or 3 or 4 bulbs and they light where t5 went backwards and if a bulb fails it takes out its partner bulb as well…

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