If I buy a HID system that says it's 400w, does that mean that it's simply a 400w bulb included? If so, would there be a problem with just replacing the bulb with a 600w or even 100w bulb in the future? For instance; http://sunshinehydro.com/cart/customer/home.php?cat=431 They have 400w and 100w but I don't see any difference in the actual hardware.
The bulb is only part of the equation. The bigger issue is the size of the ballast that provides the juice for the bulb. A 400w ballast will not work with a 600w or 1000w bulb and is a high risk for fire.
Ah thanks I completely forgot about that. Next question would be would I be able to use a 1000w ballast with a 400w or 600w bulb?
Yes, you can use a lower wattage bulb than the ballast calls for, but I'm not sure why you'd want to.
Financial reasons. As of right now, my main source of cash for this is restricted so I was thinking of initially using 400w or 600w lights but would like the option of upgrading to a larger size once we go larger after the initial grow. I guess I was confused as to whether the ballasts were bulb specific which if they were meant that more money would be needed down the road. It's good to know that I can just buy the 1000w ballast and use the same one in the future Thanks