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T5 vs T8 Grow Lights: Which is Better?

Last updated: April 19, 2020

GE Lighting

Choosing the right lighting source for your indoor grow can mean the difference between a successful veg, flower, and harvest, or an underwhelming yield. But how can you determine what sort of grow lights you need for your unique situation?

While many lighting options aren’t too expensive, choosing the wrong type can mean a costly loss of time and effort for your indoor grow. Let’s look at how to decide between T5 and T8 grow lights, so you know exactly which one you need.

T5 Grow Lights Explained

T5 bulbs are the latest generation of tubular style lighting, with a diameter of 5/8ths of an inch.

Considerably more efficient than their predecessors – the T8 and T12 bulbs – T5s boast a higher brightness output with less energy used per lumen produced. You can also find them in a high-output (HO) option that increases their brightness and efficiency even further.

Why Should I use T5 Grow Lights?

Because of their increased efficiency, choosing T5 grow lights will cost you substantially less in electricity bills in comparison to T8s. This is especially noticeable during the vegetative growth phase, where you might have lights on 24 hours a day.

If used during the flowering phase, the maximum lumen capacity of HO-style T5 bulbs can lead to greater yields of more potent and aromatic flower.

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Downsides of T5 Grow Lights

Though wonderfully efficient on the energy consumption front, T5 lights do have two major drawbacks:

First, they may have a slightly shorter average lifespan than T8 bulbs, as explained by the fine folks over at the NLPIP. While this may not be a great cost concern for small grows (with each T5 bulb costing between $2.50 to $12), it may be something you want to consider if planning larger-scale indoor grow operations.

Second, T5 bulbs tend to produce more heat than T8 bulbs. If you’re looking for a lighting solution for a closet setup without ventilation, this heat could lead to unsuitable growing conditions at any stage.

Pros and Cons of T5 Lights

Pros
  • Greater energy efficiency
  • Saves on electricity bill
  • Brightest of all T style lights, with a higher lumen capacity
  • High-output option available
  • Better for veg and flower phases
Cons
  • Produces more heat (bad for cloning, seed, and rooting)
  • Slightly lower average lifespan
  • More expensive per bulb

T8 Grow Lights Explained

The most common of all T style bulbs, T8s are a tubular style of lighting with a diameter of 1 inch.

Coming one generation before T5 bulbs, T8s are slightly less energy efficient – but more likely to fit into a wider variety of housings without having to make any modifications. Whereas T5s cannot be interchanged with previous generations, T8s can be.

Why Should I use T8 Grow Lights?

Though they may be less energy efficient, T8 grow lights also produce less heat. Why would you want less heat? This becomes especially important during the early stages of your indoor grow.

If your setup is prone to overheating due to lack of appropriate ventilation, being in a difficult growing climate, or growing during peak summer season, T8s may be a better choice for you during the cloning, seeding, and rooting phases. Here, they will provide sufficient lighting for germination and deep rooting without running the risk of scorching or drying immature plants.

From there, you could consider transferring your (now hardier) plants to a brighter, warmer lighting situation – without fear that they will be damaged.

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Downsides of T8 Grow Lights

Depending on the scale of your indoor grow project, the cost in energy efficiency of using T8 bulbs can grow exponentially. For this reason, we recommend considering more energy-efficient lighting options as you continue to expand your growing operations.

Ideally, T8 grow lights are more suited to the earlier stages of growing; their lack of maximum capacity for lighting can hamper and impair growth during the veg and flowering stages.

Pros and Cons of T8 Lights

Pros
  • Less heat production
  • Better for cloning, seeding, and rooting phases
  • Longer average lifespan
  • Cheaper average cost per bulb
Cons
  • Less energy efficient (higher power bills)
  • Lower lumen capacity
  • Not as suitable for veg or flower phases

How to Choose the Right Grow Light

Rather than thinking of the T5 and T8 grow lights as being better or worse than one another, we encourage you to consider how they might be used in a complementary fashion to ensure the optimal conditions at each stage of your indoor grow.

For use in cloning, seeding, and rooting: Choose the T8s

Because the T8s give off less heat and less light, they are in fact more suitable for these early phases. If you were to use a brighter, hotter T5, you would run the risk of scorching the plants, or upsetting their biological rhythm necessary for the early stages of growth.

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When it comes time for the vegetative and flowering phases: The T5s are your best bet

Once your plants are set up to thrive past their initial growth, you really need the higher brightness capacity of T5 grow lights. As photosynthesis really starts to ramp up during these growth phases, the more light you can provide to your plants, the better your final outcome – and heavier your harvest!

However, if you must choose just one: Use the T5 grow light

While you can adjust for the greater heat of the T5 by improving your ventilation or fine-tuning the light’s distance from your plants, there are no fixes that can brighten up a T8 to the point that you’ll be satisfied with your results in the veg and flower phases.

Conclusion

Taking the time to select the right lights for your indoor grow can make or break the results. When choosing between T5 and T8 grow lights, select appropriate to the growing phase that you need a new grow light for – and if you have the money for it, split the difference by including both types of grow lights in your setup. In our experience, that is the surest way to a successful experience at every stage of the growing process.

Featured Image Credit: GE Lighting, Amazon