Better explained....

[Jraef]

I've got some issues with you're guide above.
Mostly that your T8 lamp is about half the efficacy it should be.

From my own excel file that I made from catalog information. All of my numbers are based on maintained lumens since that is what I design to. Max lamp wattage is 400 because I don't use anything larger.
...

Actually, no argument from me. I was going strictly off of lamp data from one manufacturer and a report done by PG&E on area lighting, so I have no more info than that. I mainly wanted to get across the idea that replacing HPS lamps with Halogens was not an energy-wise idea.