Can you run a breaker from another breaker if amps are same?

I was thinking about running an individual break box w/ 10 or 12 gauge wiring from a dedicated breaker in my breaker box.

My idea set up is this:

1000 Watt HPS
400 Watt MH
4ftx4bulb T-5
Couple big fans and a few smaller ones.
Maybe a heater for out freezing cold winters...

I have around 18 amps to work with here folks (20 amp breaker however the only thing that sucks out of that breaker is a small shop light and a 75 watt light bulb. I would have to run the wiring to that room anyway and figured might as well give it it's own breaker box.

I'd like the fans and veg lights to run on it's own breaker in the breaker box, with the hps&mh on it's own breaker or maybe just the HPS.

Got my card around 6 months ago and want to grow for another patient (He is gonna supply all my equipment!) so I am thinking it's time to give it a shot. I've assisted in several other grows.... anyhow do you think it's an idea worth pursuing? (The room that is w/ the separate breaker)

Thanks,
PDX

Amps X volts = watts
So you have 18 amps X 110 volts = 1980 watts maximum

Yeah, I got that part of it what I was thinking was running an individual breaker but I guess it's pointless in the end eh?

I wouldn't hook in another breaker. You already have one,thats all you need.

You could run a 10/3 copper loomex from a 30Abreaker in ur main panel,to a 6 or 8 breaker sub panel in or near your room. that would give u 120v and 240v ,enough to take care of any future changes ...and u have proper protection at your breakers in the sub...hope that helps :)