I have 4 plants growing in a 3x3 with a 400 hps it's doing just fine. How effective would a 250 cfl bulb ? I don't really wanna waste the electric . I turn it on and barely seen any difference in the tent.
I have a 4 x 4.5 walk in closet that runs very efficiently with a 400 watt HID augmented by 210 watts of CFL; I alternate between the HPS @2000k paired with @6500k one month and MH @4200k combined with @2700k the next in an effort to expand the complexity of my finished bud. I've been accustomed to working short and sweet (12/12 from seed) but have evolved to accept that I'll bring home more bacon working with bigger plants. My new routine is two months in veg in a separate room (114 watts of LED on 18/6) for two months before a three month flowering window in the big room. My earlier quick route would have things done within about 120 days from seed while this new pattern takes 5 full months but runs as a perpetual with three concurrent waves providing a harvest each month of four to six mature girls (room for sixteen 5 gal on the ground floor but also have room for another ten in 2 gal on shelves above. The picture below is from a harvest cycle before this system was established.