Effectiveness of T5s for Autos


I’ve been trying to do a bit of research as it get time to consider moving indoors. I’ve seen that some people have been having decent results veg/flowering their autoflowers with 6400k t5 bulbs. I’m very new when it comes to the subject of lighting, but it does seem that if it works well the value behind a t5 setup both from initial costs and running costs could be huge vs some of the other lights out there.

A store near by has a setup that is 2x2x5 and comes with 250w of T5 fixtures. 4x - 4foot (one for each corner) and 2x 2foot for the top of the tent. Would something like this be worth looking into? Would it be advisable to look into LED vs t5 bulbs? Any help and advice would be greatly appreciated. Thank You!


I use a diy fixture of 6400k T5s at 250 watts for early veg. After about 4 weeks I have to switch to a more powerful LED light. My first grow was all CFL until the last 4 weeks of flower and it took some big CFLS to keep the plants happy. The problem is the heat they give off which makes it much harder to keep the grow room below 80° @Mini


The problem is that with fluorescent lamps you will need about 50 watts per square foot. So a 250 watt setup would handle a 5 square foot grow tent, which is probably smaller than the fixture footprint! A 4 x 4 tent would take 800 watts. It’s hard to pack 15 four foot 54 watt T5s into a 4 x 4 fixture. It’s a bit easier with CFLs because they have a smaller footprint. Still, you need 35 of the 23 watt CFLs for a 4 x 4 tent.

It doesn’t matter much what kind of light you use, 800 watts is 800 watts. T5, CFL, HID, or LED, you are going to have to have a top vent and duct fan to pull the heat out of that tent.


These pictures I am going to upload are being grown under 1 T5 HO 4ft. light with 2 6500 LED Veg. and then when I switch to 12/12 I use 2 6500 bloom LED bulbs…just to give you an idea…

And all pictures are of photo plants…

I have a short ceiling height of 5ft so they are working just fine…

Hope this helps you decide…as you I am under a tight budget and have to save money …


It’s strange how few people understand watts is heat. I’ve seen quite a few people mention that they have a 1500w or 1800w LED light in a 4x4
tent thinking it’s actually that wattage. Could you imagine trying to get rid of that much heat. A small AC unit would be mandatory for 1800 watts even in 8x8.


A room-size electric space heater is typically 1800 watts, because 1800 watts is all you can pull on a 15 amp circuit. My DIY LEDs run 900 watts at the wall, and I used the waste heat to heat my whole house last winter. I never had to turn on the gas heater once! Don’t tell me LEDs produce no heat…


Thanks Everyone, I didn’t realize that the heat would be such an issue with t5s, do they run a lot hotter than the LEDs that people have been using?


The heat from the tube itself is one thing, that’s generally hot at the ends and cool in the middle as a T5 is a low pressure mercury vapour discharge lamp, but the heat from the ballast added to that makes a difference.


I tend to disagree…I am using 2 T5 HO with 2 LED 6500k in each fixture in a space of 10x8x5 height and haven’t had a problem, in fact thats why I went with the LED’S lower heat and cheaper electric. To each his own but I am happy for the first grow…will upgrade when I can…


Watts are watts. There is no getting around that. Watts are energy and energy does not just disappear. 400 watts of T5s, or LEDs, or HPS all put 400 watts into the air around them. The HPS bulb heats the air immediately around the bulb to a higher temp and the T5s or LEDs heat up a much bigger area so nothing gets that hot. But the temperature of all the air in the tent is exactly the same for all three. If you have a circulation fan running, it may actually be more effective to use a cool tube around the HPS to pull that very hot air out of the tent, and get a lower tent temperature. Circulation fans warm up the air in the tent by sucking heat out of the T5s or LED heatsink.

The way your light source can make a difference, is that T5s will be less than 100 lumens/watt, HPS can be 133 lumens/watt, and very good (and expensive) LEDs can be more like 160 lumens.watt. So instead of 400 watts of HPS you could use just 250 watts of LEDs, to get the same amount of light. Then you only have a 250 watt tent heater to deal with. But be careful, cheap LEDs can be less than 100 lumens per watt.