Whenever there is talk about fluorescent lights there will always be a debate about whether T5 or T8 fluorescent bulbs are better. But you can’t simply say which kind of bulbs is better because they have significant differences that need to be recognized and taken into consideration.
But before we look at these differences and make out whether T5 or T8 bulbs are more suitable for you we should establish what the codes T8 and T5 really mean. T is a code for what the light manufacturers call tubular, because these kinds of bulbs really are in tube shape. But the fallowing number stands for the diameter of the bulb measuring in eight of an inch. And here is also the first difference – the size. The T5 bulbs are 5 eights of an inch (15.8750 mm) in diameter, whereas the T8 bulbs are 8 eights of an inch (25.4001 mm) in its thickness. So the T5 bulbs are a little thinner and therefore a little more compact.
The next thing everybody wants to know is the efficiency of each light and which one is more efficient – which will consume fewer watts but emit more and better quality light? To accurately determine the efficiency the application of each light needs to also be taken into consideration, because the application is a huge factor to how the light will perform. But if both lights will be put in the same conditions and to do the same time, for example used as grow lights, then the efficiency differences are pretty visible and we can look at these differences with the help of three measurements. The first is the Color Rendering Index (CRI) that determines the quality of the emitted light. This for both bulbs is similar – 85 CRI, which is very good, but in the two other categories you will see the T5 superiority over T8. The quantity or the amount of the light that is emitted usually is measured with the help of lumen per watt ratio (LPW). The T8 on average will emit 92 lumens per each watt that these bulbs burned electricity whereas the T5 bulbs will emit about 103 lumens per watt. For LPW ratio this 11 lumen difference is pretty significant and will result in much better outcome aka yield if you use these bulbs as grow lights. And lastly the CU or Co-efficiency of the utilization of these bulbs that tells generally which bulb is better. The CU for T8 is 76 but for T5 it is 90. That is an even more significant difference and means that the T5 bulbs really are more efficient than T8 ones in all categories that attribute to the efficiency to a light bulb.
When you are searching for bulbs the descriptions of any bulb always includes the life expectancy of bulbs. The lifetime of the T8 bulbs usually lasts for up to 24,000 hours but the T5 bulbs – up to 36,000 hours on average. But keep in mind that the T8 lights are much more sensitive to any vibrations, frequent on/off switching and other outer factors that can significantly shorten the lifespan of these bulbs, where as the T5 bulbs are more durable and they won’t be as hard to damage.
Another often mentioned criteria is the performance conditions or the conditions that are suitable for bulbs and in which they will perform to their maximum. For both bulbs they are able to work in very cold and also very hot conditions, because they are designed so that they can be used indoors as well as outdoors. Although in this field the T8 bulbs outperform the T5 ones, because they are able to endure more extreme conditions, thanks to the fact that the creators of these lights have pressed them to be very durable and only then very efficient. So if you know that you will be using these lights outdoors where, in its lifetime, they will have to endure snow and cold weather as well as sun and very hot weather I would suggest to go with the T8 bulbs. But if you plan to use these bulbs indoors then the better choice obviously is T5 bulbs.
Speaking of temperatures and heat, one of the most asked questions relating T5 and T8 bulbs are do they emit any heat and if so, how much? Both of these bulbs obviously have some heat emission, because it is almost impossible to create a bulb that won’t give out any heat. The T8 bulbs are a little bit cooler to touch when they have been running for a while. That is because they emit less light and therefore have to work less. The T5 lights will be little bit hotter and will give out a little bit more heat, but for this heat you will also get better and more efficient light. So you need to determine whether you can live a little hotter bulbs and get better results of you absolutely need cooler bulbs and lights, as it could be in very small grow room circumstances. But if you look at the total emitted heat then T5 bulbs will give out less because they are more efficient in light production and energy can be made either into heat or into light and more efficiency means less heat. They seem hotter because their surface dimension is smaller and thus it gets hotter!
And lastly a significant factor that people consider upon buying anything including bulbs is the price. Usually a T8 bulb costs from 1.75 to about 2.50 dollars depending on the manufacturer. But T5 bulbs are much more costly. They cost between 5.50 and 10.50 dollars. That is a significant difference in the price to be considered. And although the T5 bulbs are more efficient and outperform the T8 lights, you yourself have to decide whether the cost difference is worth the price difference. But if you would ask me – I’d say that the T5 bulbs are well worth the price.