quoting:
You should use them where you can incandesants put out 15 Lumen per
watt CFLs 45-65 LPW. T-8 40 - 80 LPW, and T-12 50- 110 LPW.
Some are almost 10x more efficient than incandesant.

110 sounds awfully high for T12. T12's tend to be a little less
efficient than the modern 17 and 32 watt T8's. Also, the ballasts for
modern 17 and 32 watt T8's tend to be higher efficiency electronic
ballasts that also make the bulbs operate slightly more efficiently (at
least in part by using high frequency to stop the "oscillatory anode
fall").

- Don Klipstein )


Old school T12 systems do about 60 lpw. New T12 ballasts with decent 70cri
lamps will do 72 lpw. The typical, basic T8 system going in today do about
84 - 90 lpw. A high end T8 system with the best ballasts and the best lamps
can do 100 lpw.

When I figure in the long term increased maintaince costs with a cheap T8
system, the money you save isn't that great compaired to a good T12 system
doing 72 lpw. Sadly, this is a very common occurance. Many, Many store
owners are still thinking of low initial cost. That EPAct law didn't
change a thing. The key is quality, always buy quality.