Re: It's simple, nobody was thinking.
"100*30=3,000 watts continuous power use. He bought an air con that removes 1000 watts. I asked him where the other 2,000 watts were supposed to go, got a blank look."
Will a single 60 watt lightbulb in a room with no aircon will eventually be hotter than the surface of the sun? would extracting 3001 watts from a room using 3000 hit absolute zero sometime?
OK 3000 v's 1000 seems obvious and insufficient, and good for fag packet* maths, but don't forget conductivity and heat capacity of the walls/floors/ceilings, solar gain through any windows, airflow, pressure pockets, insulation etc. it's not rocket science but it is engineering science.
I've seen a server room (a real one, that could remove more heat than the servers could ever produce) cook because the aircon cooled pockets of the room and when a server caught fire the airflow was so badly engineered that the smoke detectors only ever had clean, cool air blown over them.
A 3Kw may not be good enough by itself, conversely 1Kw may be fine, for a hobbyist, just ramp it up to 5Kw and you'll probably be OK, probably, without calcuating for all these other factors you really don't know, an extra $300 for a higher 5Kw "overspec'd" aircon won't be an issue, but you can't do the same thing on the enterprise scale. Perhaps somebody made this exact mistake, someone who thought it was simple, was working to a budget, added up the power usage and thought that would be good enough?
*fag packet, for US readers may not mean what you think it does.