Difference Between T5 and T8

Is there a real significant difference between t5 and t8 lighting? It depends on what part you study. The lighting aspects are one thing and the cost is another. With this fluorescent technology the t5 lighting could actually cost you twice as much as the t8 lighting.

The “T” in the t5 and t8 is just an identifier code that tells you the size of the bulb. Because of all the emphasis being put on energy conservation these days, these codes help people determine the efficiency of the bulb as well as the lamp tube diameter.

Facts and Figures

The t5 bulbs are about the size of a dime in diameter. The t8 bulbs are around the same size as a nickel. That means a t5 bulb is smaller. At first glance it would appear that a t5 bulb will give you the most efficiency due to its smaller size. However, when you consider the costs involved you might come away with a different opinion.

The standard t8 lamp stands about 4 feet high and costs somewhere between $3 and $5. The standard t5 costs you from $5.50 to $12.00. That should tell you that it will depend on how you use the bulbs as to which one gives you the best bang for your buck.

You are paying twice as much upfront for the t5 and what needs to be considered is the performance. Does the t5 outperform a t8 by that same “twice as much” margin? In some of your lower level interior application you’ll find that the difference is actually hard to distinguish.

Light Quality

One of the main components when determining light bulb efficiency levels is light quality (lumen output or brightness). You need these figures to make an educated determination of the bulb’s efficiency.

When all is said and done and measured accurately, the difference between the t5 and t8 depends on the application. It takes factoring in the technical aspects along with the costs to come to the right conclusion.

One of the ways of measuring brightness is to compare CRI (color rendering index – light quality) and LPW (lumens per watt – light quantity). When you compare the two using these light quality and quantity measuring tools you find that the t5 ties the t8 on the CRI and barely beats it on the LPW (t8-90LPW and t5- 99LPW). So the t5 does squeak by the t8 when figured by CRI and LPW, but again, the application will play a huge role.

A person should take the above figures and consider how they can justify the increased costs involved in the fixture, the lamp, and the ballast that they incur with the t5.


All of these lighting systems (t5,t8,t12) and others, are constantly being tested out in various settings like factories, schools, office buildings, parking garages, and in extreme weather conditions. When it comes to extreme applications, the t5 just doesn’t have a proven track record.

While the manufacturers may still be working out all the bugs, the t8 is already tried, tested, and proven and has a lower purchase cost. The t5, however, is still considered a ‘premium’ product and has yet to realize the costs of research and development.

Advantages and Disadvantages of Both the T5 and T8

T5: Advantages

  • Better Light Control.
  • Smaller Cross Section and Size.
  • Smaller Ballasts.
  • Various Lengths.
  • Good Color Rendition Availability.
  • Good Color Temperature Availability.
  • Better LPW (lumens per watt) Efficacy.
  • Better Photometric Performance.

T5: Disadvantages :

  • Differing Lumen Outputs Among Manufacturers.
  • Changes in Light Output Between Enclosed Luminaries and Bare Lamps.
  • Changes in Light Output Between Indirect and Direct Luminaries.
  • Vertical versus Horizontal Burning Variables.
  • Lumen Variations between 25 degrees and 35 degrees Resulting in a gain or loss of 10% light output.
  • Reduction of Lamp Life when PS is Not Used (IS is good for long-term use).
  • Position and Temperature Sensitive.

T8: Advantages

  • Industry Work-Horse.
  • Come in Various Color Temperatures, Color Renditions, and Lengths.
  • Less Fragile When Compared to a t5.
  • Easy to Use For Replacing t12s.
  • Energy Efficient.
  • Good Lumens at ‘End of life’.
  • Uses PS When Sensors are Deployed.
  • Costs Less Than the t5s Now.

T8: Disadvantages

  • The IS and Sensors Reduce the Lamp Life.
  • The Lamp Contacts Cannot be in Contact with Grounding Areas.
  • Lamps Fail When Replaced Without Shutting Power Off.
  • Lamps are Incompatible With Ballasts.
  • Lamps Fail When Not Being Used in the Ambient Temperatures They Were Designed For.
  • The Ballast Factor

All of your fluorescent lamps operate using ballasts to maintain the current that passes through the lamps at certain values. There are basically 2 main types of ballasts –

1. Electromagnetic Ballasts
2. Electronic Ballasts

and the electronic ballasts are the more expensive of the two. However, they are also more energy efficient and over time can save money. They also generate less heat while in operation and save on air conditioning energy.

Final Thoughts

It comes down to the fact that a t5 creates more usable light than the t8. Even though that’s true, it is not so superior that it renders the t8 as being obsolete like the t12.

There are future LED technologies that are expected to make both the t5 and the t8 obsolete, however, they are still in the making and have not made their way into the mix as of yet. So for now, the battle continues between the t5 and t8 in regard to energy efficiency and use in various applications.

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