Remember this from my mother thread? The fixture in the bottom of my mother area is not drawing 40 watts, itâ??s drawing 80, since it has 2 40 watt bulbs. So for 67% of the electricity, the T5 puts out about 21% more lumens, according to my light meter.

T12 are the older, bigger fluorescent tubes, T5 are the newest, smallest and most efficient, and T8 is somewhere in the middle. One of my 4 foot, 54 watt T5 bulbs is putting of 21% more lumens than a combination of 2 of my 40 watt T12 bulbs. The T12 combo costs 33% more in electricity. The downside is that (to my knowledge) T5 bulbs are not made in the proper color for vegging or budding, where as the T12 bulbs are, or are at least a lot closer. The proper color being 5700K and 2500K respectively.

Let me know if that doesn't clear it up.