if you ever get down to it. go to your library and see if they have a free energy kit you can check out.

it ususally include a kilo watt meter. you plug the meter in you plug your computer in and wait a week and it tells you how much power it used on average. thus you can get data.

however i did the math. a small window ac is about 1 kilowatt. so runnign for a day is 24 wkilowatt hours. for a month is 720 kilowatt hours. at about $0.10 per kilo watt hours the ac is probably half of your electric bill. now if you have a whole hours ac that can be twice and even three times the cost of a window ac.

so becaue you said ac i suspect 99% of the electrical cost/complaint is the ac.

a new pc with solid state drive and flat screen LED monitors will use much less power than a old crt tv.

so if your room mate gets nit picky, i suspect it first may be time to set up finding a new room mate. or a new apartment. it generally only gets worse. but kilo watt meter to measure actual power usage if they demand proof. and like you said no ac should signifcantly reduce electrical bills. a box fan in a windows blowing directly on you is much more efficient of a way to stay comfortable than ac cooling the entire house.