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T8 or T5

Created 1/19/2012 by Pat Lydon
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I've encountered several situations recently where I've been comparing T5 vs. T8 as a choice in lighting retrofit projects and space remodels. I know that there are many details to consider including:
- lighting requirement for the space (fc, CRI, lamp life, color temp, etc)
- fixture style and design
- ceiling type (reflective surface or ?)
- ceiling height
- indoor or outdoor; ambient temperature

.. and I'm sure the list goes on... and on...

But - I'm often running into a general opinion that T5 and particularly T5HO is the logical choice for a retrofit simply because they are assumed to be more energy efficient.  I've looked at several recent proposals where incentive documentation has shown T8HP to be more energy efficient than T5HO.

I'd like to hear thoughts from other CONDUIT community members on this topic. The most common applications in my organization where this has come up have been:
- interior office space (open cubicle environments)
- parking structures (mix of above and below ground multi-level)

Thoughts? Opinions?
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Comments (5)
Jim Volkman on 01/20/12 on 07:56 AM (Pacific Time)
Interesting topic.  Are you referring to actual energy efficiency between T5 and T8 technology or cost effectiveness?  

From an energy efficiency perspective I don't see T5 vs. T8 technology a game changer, but certainly the T5 is a more efficient technology.  But as you note the application defines its effectiveness.  In particular in new lighting system installation (existing or new construction) the opportunity to have fixtures designed for the lamp type and the flexibility for layout and reduction in fixture count provides a great opporutnity for T5 to be both more efficient and cost effective.  

If you're looking at a one-for-one lamp replacment, a different story.  A T5 lamp is around 12% more efficient than a comparable T8 lamp, but can cost much more, as much as 4x more.  Also the published lamp lamp life of a T8 is longer than the T5 (24,000 hours vs 20,000 hrs.)  Ballast factor and lamp location will have some impact on lamp life as well. 

So if the lamps need to be replaced more, but you reduce the operating costs through higher efficiency, what's best?  This really starts to get to the idea of "Total Cost of Ownership" being the best desicion making method.  All of the factors need to be considered in what you're going to have to pay for that lighting system (first cost, energy, and maintenance cost.)
David Harris on 01/20/12 on 09:01 AM (Pacific Time)
Sources I found indicate that T8s are typically 3%-15% more efficient than T5s (on a lumens per watt basis).
A concise list is at www.p-2.com/cutsheet/technical/tables_of_wattages.pdf
Another good comparison is the BPA Lighting Calculator.
John Wilson on 01/20/12 on 12:17 PM (Pacific Time)
Great conversation everyone! My operationally excellent commercial team turned me onto this posting (Thanks Rick!) To opine from a BPA perspective, I would just come back to the fact that it is all about energy savings. If your baseline is a warehouse with 400 watt metal halides and you are trying to decide between 6 lamp T5 or T8 I would say... if you can get the job done with T8s we are going to save a lot more energy. We will incent the T5 option but at a lower rate. We typically see this question come up when ceiling height becomes an issue. In the applications you described (interior office space and parking structures) certainly the issue of design comes into question. T5 and T8’s are both great technology and every job has its subtle nuances- In my opinion there isn’t a clear winner, you have to balance the customer’s needs with energy savings and total cost. Hope this helps.
Pat Lydon on 01/20/12 on 12:47 PM (Pacific Time)
Great comments everyone!

Jim - I was referring to energy efficeincy performance of T5HO vs. T8HP... but really it is the total cost of ownership we're most interested in. Longer lamp life, cost of replacement lamps, additional carrying costs if you're adding yet another lamp to the onsite supply inventory, etc.

I know that T5 and T5HO have been used effectively in a number of application types and particularly in new contruction where they are designed in during the lighting plan/design but I've seen a number of situations where they are being recommended in a retrofit situation. In these projects they are often being proposed on a 1 for 1 replacement for existing fixtures so no one is taking the time to maximize the benefits of T5 and potentially better light distribution.

Too often I find the decision makers in these projects are simply assuming that T5HO is bound to be more efficient than a T8 solution.... I'm also starting to wonder if  the contractors that are proposing them may be getting incentives/bonus commissions (or "spiffs" in channel parlance) to push T5 solutions to increase adoption.
Jack Canan on 01/22/12 on 11:55 AM (Pacific Time)
Good afternoon everyone,

I am a new member to Conduit and stumbled on this discussion. I am a NV based ESCO working throughout the US, especially on the east coast. I want to say that my experience and training has shown that T8's are far more efficient then T5's and in fact I've replaced T5's with T8s and saved enough money for my client to allow him to finance his entire retro-fit from that savings.T5's are not a standard fix for all as some make it out to be and I agree with Jim above that the lamps cost around 4x's that of a T8 5000K lamp.
So when you drop from 465w HID to T5s you are reduced to around 315w and with T8's you'll be at 221w. I also deploy a system that can be hung @ 123 feet in the air and hit the floor with improved foot candles above that of the original 1000w or 1500w HIDs were producing. This system deploys T5's and advanced technology to accomplish this task - where as my T8 fixtures can be used to 50ft /- for 400 watters depending on the situation.

Pat - I agree that there are plenty of companies out there that their only products consist of only T5 fixtures - so they will push that all day long to get paid - I have had 1st hand experience with this numerous times. The really good companies have a variety of products to handle each client's situation. My product suite consists of LED, induction, fluorescent (T8 and T5), Plasma, skylighting, wind, solar and the financing to install it all - new or retro-fit.

I look forward to your comments.
Thank you,
Jack Canan
Sight Line