UPDATED: April 25, 2019.
Professionals cannot seem to rest the debate of T5 vs T8 Grow Lights and state why one is better than the other. So, in this post, we will try to look at the main similarities and differences between these two grow lights in order to give you an opportunity of making an informed decision in case you decide to buy one.
Table of Contents
What Are Grow Lights?
A grow light is a multi-tasking light bulb that replicates the energy and impact of UV rays or sunlight exposure to plants in all stages of the plants’ life. This light enables the user to grow plants indoors or in locations with poor weather conditions.
What Is The T?
The T is simply a code that identifies the size of the bulb. It designates the level of energy efficiency and the lamp tube diameter.
T5 vs T8 Grow Lights: Which Is Better?
We will consider different features and factors in order to determine which the better grow light is between the T5 and the T8.
1. Quality of Light/ Efficiency
The T5 grow light edges out the T8 grow light when it comes to the efficiency of these lamps. The T5 has a better lumen to watt ratio, meaning that its output is more powerful and brighter per single watt of energy than the T8 does. The other thing that makes the T5 the better light when it comes to efficiency is because its light is more focused and concentrated in a single spot due to its smaller diameter (this means more watts/cubic centimeter).
Due to providing more watts/cubic centimeter, T5 grow light is preferred for plants that are about to flower because they need more intense light. Another argument that makes T5 the better light for flowering is that since the T8 bulb is less powerful; you will need to put it closer to your plants in order to provide the same results as T5.
However, if we look at the actual quality of the light, the T8 becomes the better lump since it has less glare and hence, more qualitative for home use and almost the same for growing plants. T5 light is stronger and brighter than T8 but with lots of glare.
Tip To Help You Out: Here is a little comparison to help you understand the difference in T5 and T8 efficiency. A 4 lamp HO T5 light can be used as an ordinary 400W metal halide whereas a T8 light will require a 6 lamp one.
2. Heat and Temperature
If you assume that T5 and T8 bulb are of the same size (which is not possible), then the heat they produce is almost equal, however, the bulbs themselves will have different intensity of heat. The T8 grow light is cooler and hence safer to touch because its heat is produced from a larger area making it heat up less compared to T5 (which is smaller).
And if these lights are hot, the T5 bulb is highly likely to kill your plants if they touch it compared to T8. Again, your plants can be near the T8 bulb since it is cooler and still feel comfortable. But you should note that the T8 bulb isn’t 100% cool; it is impossible.
When it comes to the temperature, these bulbs can be operated in any kind of temperature, making them last longer especially if they are of high-quality. The important thing to note is that T8 works efficiently at 28 degrees Celsius while T5 works efficiently at 35 degrees Celsius, a difference of 7 degrees.
Tip To Help You Out: You should get the T5 grow light if you can place it 4-8 inches above the plant (get the T8 if space is less). With that said, you can still place your T5 bulb below 4 inches if your room is well ventilated and remember to water your plants regularly (this will also enable you to move the T8 further).
3. Spectrum/ Color Rendering
Color rendering of T5 and T8 are almost the same, so when it comes to spectrums, they are almost the same. However, you need to remember that it doesn’t mean that their brightness will be the same since the T5 is brighter than the T8 and there are different models that provide full spectrum or primarily blue/red spectrum light.
So, we would recommend you to note the temperature of the bulb you want to purchase.
These bulbs have almost an equal lifespan. If you apply the 12/12 light cycle, they will both last for about 36,000hrs. However, the T5 grow light is more durable in its lifespan as well as degradation. The T8 model is more sensitive to frequent off/on switching and this will reduce its lifespan significantly.
A reduced lifespan of T8 due to frequent on/off switching means that you will need to replace it regularly and hence use more money – it will be more expensive than buying the T5. Note that, it will be cheaper to buy the T8 if you intend to install it in a place that requires light 24/7; it will last just like the T5.
When it comes to the use, the T8 was mainly used for cuttings and seedlings in gardening as well as other agricultural places. The T5 was mainly used by aquarium owners. However, both of these lights are today used and can be used to grow plants for commercial purpose and at home and also provide superb side lighting in the greenhouse.
So, you can only be limited by your imagination when it comes to how you can use these two fluorescent tubes.
If you are looking for a cheaper light, T8 is your best bet. But they almost cost the same, with T5 being just slightly more expensive.
A T8 grow light has a diameter that is roughly the same size as a $.05 nickel while a T5 model is similar to a $.10 dime. Therefore, the T5 is smaller than the T8.
The T5 vs T8 grow lights debate cannot be solved exhaustively. These lights have both similarities and differences which make it impossible to choose the better light of the two. Know your need before you choose a specific model.