My house AC at 77 my aquarium usually is 79-80 on average and once in a while 81 degrees. When it hits 80 i open the window at night and have fan blowing air in, by 8am morning its around 77-78. From my observation, aquarium temp on the most part will be 2-3 degrees higher then house temp.
I am getting tired of constantly monitoring temp, turning on fan, opening windows, etc. I'm going to install chiller and not have to worry about it too much.