did u say light from window ?
CFL r cheap br0 i get 105 watts(=500 actual watts) cfl for about 10USD
Sorry dude but that cfl is actual wattage = 105 watts, now if you twist the maths and use non plant specific lightspectrums yer you could say it may have the equivelent light output as a 500watt incandescant.
Ok so lets test this far out claim!!! Put a 500watt incandecant into the mains and blam, your blinded by the light, now put that supposed 500actual wattage!lol! real wattage 105watts in the mains and guess what, it still sucks even for 105watts.
I grow with 2x250watt cfls in red and blue and its barely equivelant to 250watts of hps so go figure??? Those cfl ratings are make believe and involve one inch of penetration let alone a plants worth. If your gona quote that here there are those that are gona say BS!!!!
4x26watt cfls will do but expected yeild would be in the region of 15 to 30 grams max of one plant. Peace