Yes, it sure makes a big difference! We got the portable AC that has only the exhaust hose that goes out the window instead of the AC that has to be installed in the window. We run the AC for about an hour, then we can shut it off and the place stays comfortably cool for 3-4 hours (with our windows closed). When we had the window AC, we had to run it all day because as soon as we would shut it off, it would get too hot again. So, this is pretty nice.