saving money on A/C

saving money on A/C

I'm looking for ways to keep my A/C costs down this summer. I have a large duplex that has nothing but window units, and most of them are old junkers. Even with them all going full blast, during the hottest parts of summer (okay, most of the summer) it's still TOO HOT in the house and my electric bills last year got close to $300 a month. I rent, so getting new units isn't an option. I already have some pretty good insulated/black-out style curtains that work pretty well. And I know the basics: closing the blinds/curtains during the day, keeping the filters changed, etc. The problem is a) the house is BIG and b) the windows are REALLY drafty. I used that spray foam stuff to seal up holes around the units. During the winter I had those double-sticky-tape/plastic wrap window coverings on, and it did help. But the tape ripped the paint off some of my window sills, and prevented me from opening them on open-window weather days (I'm in Oklahoma so the weather often varies wildly from day to day). What else can I do? I think ideas for home-made A/Cs like these are really cool and I just might spend my Monday off trying to make one, but I am also looking for things I can do for the whole duplex (I don't see myself making one of those for every room in the place :-p). So basically my questions are, what (if anything) can you do to increase the efficiency of window A/C units? How can you seal up drafty windows, without making them impossible to open? Am I missing anything else here??
Pretties

Pretties

My Room =)

My Room =)

monarch, and a tomato question

monarch, and a tomato question

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New piece….

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A Field Trip to Home Depot…

ID help

ID help