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What's the difference between T5, T8 and T12 fluorescent light bulbs?

This is a question we often get asked at and the answer is very simple. On the most basic level, the T5, T8 and T12 florescent bulbs have a different diameter tube thickness. The diameter of T12 is 1.5 inches, the T8 is 1 inch and the T5 is only 5/8" inch. Many years ago, research found out that if they could make the light tube thinner, then there would also be greater energy efficiency associated with it. That led to development of different kinds of ballasts to accommodate the newer types of 1 inch and 5/8 inch diameter tubes. They also differ on the ballast that they are operated with most of the time. T12 primarily run off a magnetic ballasts and the T5 and T8 bulbs operate on electronic ballasts. That's not always the case as sometimes people changed their T12 ballast to be electronic years ago. But most people have them operating on a magnetic ballast. Even though the fluorescent light socket is exactly the same for both the T8 and T12, the T5 has a different light socket because the end-pins are completely different as well. Also be aware, they all operate on different ballasts. For instance, if you try to put a T12 lamp in a T8 electronic ballast, it will generally flicker a lot and have some problems even though it may light up. It's not made electrically for that type of ballast, the T8 light bulb is. It's engineered differently to operate best on electronic ballasts of various types whether it be instant start or a program start. Most commercial buildings and people that use them in their homes have the instant start ballast that operates the T5 or the T8 light bulb. So the bottom line is that these are not interchangeable and if you're going to upgrade from old to T12's to a T8 or even T5 light bulb, then you also have to change out the ballast. Most people find that the thinner lamps also provides better color rendering and you will notice a difference on that as well. So it's more than just energy efficiency, it's also the effect that it has. So those are the main differences between the three lamp types and you should be aware of that when you're changing from one to another or if you're just simply replacing what you have existing in your light fixtures right now.

I hope that answers your question, let us know if there's anything else we can help you with.

John Bolduan

Here's the light bulb products I mentioned in this article:

Displaying products 1 - 3 of 3 results
F32T8 Fluorescent Light Bulbs
F32T8 fluorescent light bulbs are a 4 foot energy efficient lamp.
Price Each: Starting at $6.56
F32T8 Fluorescent Light Bulbs

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