well there is a thumb-calculation that you get for ever W with cfls about 100 or lumen's or so, and with MH 120 and with HPS about 140. for descent flowering you will need whopping 40,000-50,000 lumen's. that is to do great and about what a 400W HPS will give you ruffly. if you go below that, it will probably take longer and you will less potential and bud out of it.

so you should look what you will be going to pay for 300-600W in floros and cfls, and what you going to pay for 250-600 in HPS and normal HPS will come cheaper...

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keep the thumb green and the gun oiled, !