T5 vs T8

T5 vs T8 bulbsThere is a lot of speculation about weather T5 or T8 fluorescent lamps are better and why one is more preferable than the other. So in this article I will try to highlight the main differences and similarities for you to make the decision on which light to buy easier.

Efficiency / quality of light

When talking about the efficiency of both lights the T5 ones are definitely superior to T8 lamps. They have greater lumen to watt ratios which means that they output brighter and more powerful light per watt of electricity than the T8 do. The T5 lamp light also is more concentrated and focused in one area because they are smaller in diameter (there are more watts per cubic centimeter in them) so the T5 bulbs are especially good for plants when they are flowering because then they want more intense light. And the fact that the T8 bulb light isn’t that powerful means you need to put the plants closer to the bulbs to give them all the necessary light. But if we speak about the actual quality of light then although the light from T5’s is more brighter and stronger the T8 lamp light have less glare and therefore it is a bit more qualitative for humans but almoust the same for plants.

A little tip: If it is hard to understand the difference in efficiency then here is a little comparison. A 4 lamp HO T5 fixture can replace a regular 400 Watt metal halide or high-pressure sodium fixture, whereas to replace it with T8 fixture you will need a 6 lamp one.

Temperature and heat

If we talk about the heat production by each of the lamps on the condition that they are in the same size, which however is a rare occurrence ,then it is pretty equal although you will get more light from T5 bulbs, but the difference is in the heat of the bulbs themselves. So the T8 bulbs are definitely cooler and therefore safer to touch because with the T5 bulbs the heat is produced from a smaller area making them heat up more. And if the bulbs are hotter then if the plant accidently touches the bulb it can get burns and other heat related damage. And also if a bulb is cooler then the plants can be closer to it because they won’t experience any discomfort from the heat of the bulb. But that being said that doesn’t mean that the T8 bulbs are completely cool too, because that is almost impossible.

But if we look at the temperatures these lights can operate in then they both can operate in pretty wide range of temperatures, making them both durable if they are made qualitatively.
A good to know thing about the temperature is that T8 light run most efficiently at about 28 C but T5 bulbs need 35 C so there is a 7 C difference.

A little tip: You should buy the T5 light if it can be hung about 4 to 8 inches above your plants, but the T8 light if there isn’t that much space in your grow room and you can hang them up below those 8 inches. But in general you can control your heat with ventilation and frequent watering so you can put T5 lights closer and also move T8 light farther . If you take this tip into consideration your plants will be happy and won’t suffer from the heat of those bulbs.

Color Rendering Index/ spectrum

Color Rendering index for both of these lamps is basically the same so in spectrums they don’t differ much. But keep in mind that even if the spectrums are the same the brightness of light for T5 light bulbs is better than for T8 lamps and there are various models that offer full spectrum or mainly red / blue spectrum light so be sure to check the color temperature before buying any bulb.


The life of both the T5 and the T8 bulbs are almost the same. If you use 12/12 light cycle then the bulbs will last you about 36,000 hours. However the T5 lamps are more durable in their lifespan and degradation. The T8 ones are more sensitive to frequent on/off switching and if you do that a lot with your T8 lamps then their lifespan will significantly decline and you will have to replace them very often. And frequent replacing means that you will spend a lot more money than if you simply buy the T5 lamp that is more expensive than the T8 one. But if your light cycles are long and you aren’t switching them on and off constantly then of course they will last as long as the T5 bulbs will and on rare occasion can even outlast T5 high output lights.


If we compare the most common usage of these lights then the T8 lamps are traditionally used more for seedlings and cuttings in gardening and other agricultural industries. Whereas the T5 lights are common amongst aquarium owners. However these lights can be and are used by growers to grow plants at home and for commercial growing and also side lighting in your greenhouse.So basically there are no limitation to what you can do with these fluorescent tubes and both the T8 and T5 work amazing!


Almost all the literature on the internet says that T5 lights are much more expensive than the T8 lights are but from my own findings I can see that it is not the case and both light come in almost the same prices and T5 light are just a bit more expensive. So if you are in need of cheaper light then the T8’s can be for you is you manage to find a great deal but if you get the same price for both models then don’t hesitate and go with that T5 lamp!




Lumen output


Average price (buying bulk bulbs)

Average price (buying single bulbs)


2 feet

17 W

1325 lm

78 lm/W

1 – 5



22 inches

14 W

1350 lm

96 lm/W

2 – 5




4 feet

32 W

2950 lm

92 lm/W

2 – 5



45.8 inches

28 W

2900 lm

103.5 lm/W

3 – 5




4 feet

44 W


90.9 lm/W

3 – 5



45.8 inches

54 W


92.5 lm/W

3 – 6



Sizing / variety

The T8 bulb diameter is 1 inch (26 mm) but the T5 bulbs are even smaller and more compact – only ⅝ inches (16mm).

Although T5 bulbs may be more effective than T8 bulbs the T8 ones offer a lot wider variety than T5 do. With T5 bulbs the main thing to choose from is the size, the color temperature and weather to buy high output (HO) bulb or very high output bulb (VHO) but when buying T8 bulb besides size and color temperature there also are a lot more types of bulbs like standard CRI, high CRI, high lumen, extended performance bulbs and so on. But for a customer that isn’t experienced in this field maybe the small amount of things to choose from with the T5 bulbs is better and may seem a lot more reasonable.


T8 lamp advantages:

T8 lamp disadvantages:

  • large variety in size, color temperatures, types

  • cheaper than T5

  • can be T12 replacement

  • bulbs don’t heat up as much

  • life span is very short if frequently switched on and off

  • less lumens per watt (efficency)

T5 lamp advantages:

T5 lamp disadvantages:

  • more efficient

  • give brighter, more powerful light

  • more lumens per watt

  • are more durable to frequent on/ off

  • good color temperature variety to choose from

  • are more expensive that T8’s

  • are shorter so they need separate fixture

  • bulbs get hooter that T8


In this next table I have gathered all the sizes of T5 and T8 bulbs that are out there to help you see all the possible options and maybe help you make the decision on which size you want to get. As you can see in that table you have almost limitless length possibilities starting from really small to huge bulbs but as I pointed out in the previous tables as the bulb gets longer it also increases in efficiency so keep that in mind!


T8 bulb lengths

11.78 inches

12 inches

14.78 inches

15 inches

17.91 inches

18 inches

23.78 inches

24 inches

25.78 inches

26 inches

27.78 inches

29.78 inches

30 inches

35.78 inches

36 inches

40 inches

47.5 inches

48 inches

59.61 inches

60 inches

70 inches

72 inches

93.91 inches

94 inches

96 inches

T5 bulb lengths

5.91 inches

6 inches

8.91 inches

9 inches

11.91 inches

12 inches

20.91 inches

21 inches

21.6 inches

21.61 inches

22 inches

22.17 inches

22.2 inches

22.25 inches

33.39 inches

33.98 inches

34 inches

45.2 inches

45.8 inches

46 inches

57.6 inches

57.61 inches

57.667 inches

58 inches

And with this table I want to show you the approximate expenses of T5 and T8 lamps if you burn them 24 hours a day during their average lifespan which is about 18,000 hours. I will take 0.10 $ for one kilowatt hour (1 kWh) to make the calculations easier.







24 inches

22 inches

48 inches

45.8 inches


17 W

14 W

32 W

28 W


30.6 $





As you can see T5 light are more efficient and they will be cheaper to run but not by much and you must take this cost into your final calculations before coming to the conclusion which one is the best. I must say that I was surprised by my findings and I had always thought that T5 bulbs are more efficient and better in any way but after all this it seems that T8 ones are not that different and that little lack of efficiency only accounts for a couple of dollars more lost in electricity. If you manage to find those T8 bulbs cheaper than T5 ones by 5$  to 10 $ then you have almost the same monetary value for the bulb and the lifespan energy costs.


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