you can use alot less in veg......if your only veging to around 1'-2' you dont need much....although a larger light in veg will produce tighter internode spacing, much much fatser growth, and much thicker stems and branches and more of them.....veging under the t-12's is like slow motion compared to a 1k....but can be done just fine.....just takes longer

I do my vegging under a 1kw MH in an air cooled hood. The internode spacing as absolutely awesome, especially compared with flouro's. I have a friend that uses CFL's, and there's really no comparison. You can even root clones under it, if you put a couple layers of cheesecloth over the dome.

Imo, part of the reason you don't need as much light to veg with is because during veg, the plants are still nice and small, and can be grouped rather close together. During flowering, your plants will double or even triple in size, requiring the plants to be spaced further apart, and needing more light to penetrate the thick canopy.

Thanks for the enLIGHTenment guys....