Was jst looking into a HPS or NMH for myself in my grow room.
Check out this page for info about different kinds of lighting and spacing that you need between the plants and lights.

Here is a link that might be useful: Plant Grow Lighting Questions

It seems to me that T5 lighting H0 is the best to buy for cost and efficiiency.

You have to weigh cost vs. lumens and the amount of space (height) you have. HSP and MH bulbs are very hot and plants must be at a distance of several feet below them. Fluorescents run very cool & plants can almost touch them. I just bought two setups of 200 watt compact fluorescents. It's my first year bringing citrus inside. It will be interesting to see what happens. I'm sure others that know more will offer their knowledge. Let us know what you end up with. Stephanie

I had mine about 3 feet below the lamp with alot of air circulation at that level blowing the heat away. There was a bit of scorch at first, but they adjusted. After all the ceiling is only 8 or 9 feet in my basement. That was with a MH 1000 watt system..

I have a few fluorescent grow light carts that I have plumeria seedlings on. They can touch the bulbs without damage. I also have two 1000 watt HID MH lights set up in a downstairs room. They give off quite a bit of heat and should probably be about 4' or more from the plants. This is the first year I've used HID lights and OMG are they bright! The room where they are set up has a large bay window and cars slow down to see what's going on at night. I'm just waiting for the police to show up thinking that I'm growing pot. lol