LED Full Spectrum VS 600 W HPS.. help please!

I'm growing sativa HAZE.. g-13 accros with Laos. complete indoor hydro, i need to grow 18 plants.

if I'm using 600W HPS, how many lights i need for good yield and to cover enough.

or if i'm using 250W Full spectrum LED?

That's a question worth asking yourself before you start.

You're going to need alot of coverage, one which cannot be satisfied by a 600W HPS. Try splitting into 4x250W or 3x400W or 2x600W. As for LEDs, you'd be needing at least 500W real drain, split into several spots. And seek known led-chip brands: OSRAM, Philips, LedEngin or Cree.

okay amazing, so lets say im going with 2x600W how much space is that going to cover? more than 150cm2?

You can always use a light rail for more coverage.

150cm^2 can be covered by like 10 Watts, that's a typo, I'm sure.

600W HPS covers 3'x3' or 4'x4' well. Two 600W HPS aim for 3'x6'. Eighteen plants in this space is a little tight, imo. How big do you want the plants? How much space do you have to grow?

-Edit- You mean a 5'x5'! >.< My bad. Two 400W's could work. Two 600W's could work even better. A 1000W wouldn't be bad either.