400 watt equal to the sun in 4X4 space? WTF?
I don't know what exactly the lumens per sq ft of the sun is. I think it probably depends on where you are in relation to the equator. I can tell you this for sure though: Anyone who has grown under a 400 and then grown outside in the SE can tell you there is absolutely no comparison. I could have been wrong about the 1000 though. The highest I ever tried was a 400 halide and a 250 HPS under the same reflector and the outdoor sun completely blows it away.