T5 Linear Fluorescent Offers Advantages Over T8 For Certain Applications

T5 fluorescent light bulbs are often overlooked as an excellent option for specific types of lighting in new construction and remodel projects. T5 fixtures can often be found in office lighting where ceiling fixtures supply the ambient illumination over workspaces. T5s are also frequently used in wall wash applications and in high bay direct lighting installations.

This post will briefly explore the key differences between T5 fluorescent and T8 fluorescent systems, and show where T5 often results in better performance, lower energy costs and lower initial installation costs. We will also compare T5 fluorescent to T5 LED lamps.

Main Physical Differences Between T5 and T8 Lamps

• T5 lamps have a diameter of 5/8" compared to 1" diameter of T8 lamps.
• T5 lamps are available only in metric lengths (and are generally shorter than equivalent T8).
• T5 lamps utilize a G5 mini bipin base while T8 lamps use a G13 medium bipin base.
• T5 lamps only operate on electronic ballasts.

Shorter tube lengths, different socket requirements and usually different ballasts make T5 unsuitable for most retrofit projects.

What Advantages Do T5s Offer Over T8?

With a focus on new construction and remodel projects, T5 fixtures offer considerable benefits for specific lighting applications.

• The small diameter of T5 lamps allows for narrower fixtures suitable for small spaces such as cabinet, display and many indirect lighting applications.
• Smaller tube diameter translates into higher optical efficiencies for T5 compared to T8.
• For suspended direct/indirect lighting in offices, T5 lamps and their reduced-size ballasts again allow smaller, visually appealing fixture sizes which result in improved optical control and greater design flexibility compared to T8 fixtures.
• T5 HO (high output) lamps have a much higher lumen output than T8 lamps with the same tube length. In most cases a 2-lamp T5 HO fixture produces more light than a three-lamp T8 fixture. This fact makes T5 an excellent, cost-efficient choice for fluorescent high bay applications.
• T5 lamps have a higher optimal performance temperature than T8 lamps (95°F vs 77°F). T5 lamps should perform better in enclosed fixtures or tight spaces.
• Shallower fixtures utilizing T5 lamps are generally more efficient than T8 fixtures.
• The superiority in optical efficiency of T5 fixtures over T8 fixtures may reduce electric energy use slightly.
• Where T5 HO fixtures are used, the fewer lamps required to produce the same light output as T8 fixtures will also result in reduced electric energy costs.
• Where T5 HO fixtures are used, initial costs may result when higher output T5 HO fixtures can lead to a large reduction the number of lamps and fixtures per project - this is especially true for large commercial projects.

How Do T5 Fluorescent Lamps Compare to T5 LED Lamps?

Note: the comparisons shown below are for T5 fluorescent and T5 LED ballast-compatible lamps. The comparison does not include T5 fixtures with built-in LED arrays.

Rated Life: T5 fluorescent lamps: 20,000 to 30,000 hours vs LED T5 lamps 40,000 to 50,000 hours

Light Output: The specs for T5 fluorescent lamps usually show a higher lumen output than the "equivalent" T5 LED lamps. For example: 54 watt T5 fluorescents range from 4000 to 5000 initial lumens, while most 54 watt equivalent T5 LED lamps are 3000 to 4000 initial lumens. The reduced lumen output from LED may be compensated somewhat by the perceived brightness factor of LED or may not be critical, depending on the application.

Lamp Efficacy (LPW): T5 fluorescent lamps: 90 lumens per watt to 105. T5 LED lamps: 105 lumens per watt to 120+.

Cost (by the case price comparison per lamp): T5 Fluorescent: $3 to $6. T5 LED: $10 to $18+.

Conclusions

While T5 is not a good option for retrofits, it certainly offers advantages compared to T8 for certain applications, and should be strongly considered for new construction projects.

T5 LED offers longer rated life and higher efficacy, but the initial cost differential compared to T5 fluorescent is significant.

Overall, T5 fluorescent fixture installations should at least be considered alongside T8 and T5 LED for many commercial, institutional and industrial projects.