I use em
30W eaqual to 150W I think, 1650 Lumens, them I use is in 2700K and cost like 6$ or so, and I use em as side lightning, they are the same as the spiral once, but shaped different ..
in general, with all tube`s/fluorescent light, is that they is strongest at the middle of the tube/spiral, and once they begin to get really dark at the ends its time to changes em as old bulbs/tubes can loose up to 30% intensity/output
also in general, keep em close, according to my light meter you need to keep em with in 2-4 inch`s for strong light at 4-10 they still provide ok light for lower growth, but after 12" my light meter don't even get a reading
hope this help some