I am looking into alternative sources of power for use in less than controlled enviroments. Atomic power is clean, if you don't mind the half-life. It also isn't available in convenient or portable packaging. Fuel powered generators are available, but they are also kind of loud.

So... what about batteries? I have seen portable auto jump start boxes, some of which have a built in power converter and 110v outlets. One says it will power up to 1500 watts, 1350 maximum continuously. Maximum output will get you 10 minutes. A desktop PC will run for 3 hours.

What I would like to know, is how big a battery would I need for say... 3-4 hours of 2100 watts worth of lights?

I don't think you will find a large enough battery system for that.
Generators seem to be used. Keep in mind that there lower noise
generators out there than others. Also, usually they are outside
recording area with extension cables and whatnot. A good mike
should be directional enough to not pick it up probably.

p.s. I've moved your post to the general forum.