Quote Originally Posted by Dyranty
t12's are big so that's why people suggest t5's, so you can fit more of them into smaller spaces.
Uhh, no.

T-12s don't take up any extra space horizontally, and they take about 1/2" more space vertically. T-5s are vastly more efficient than T12s and even T8s. I know. I have a light meter and a calculator and have both kinds of lights.

T-5 bad points: There are no proper T-5 bulbs for budding, they are around 3000K. Use them only in veg or as bud supplements. They run hotter than T12, so you can't let the plants grow into the light like you can with T12.