Let me add another one. Lower humidity. My experience has been that we rarely have a heat problem in the summer when we have the AC turned on. This is because the AC is keeping the humidity lower in the house. This increases evaporation and thus decreases temp.

When we do have temp problems is on mild days like we had this weekend with high humidity. No AC, no cold dry air, and little evaporation. I retrofitted my hood with extra high cfm fans to help during this sort of peak cooling problems. I normally have two 100 cfm fans running on a timer with the lights. I have another 2 fans available when I need them. Spring and Fall are when they get the most use.

Remember that an aquarium works like a big swamp cooler. Huge amounts of heat are given up as water vapor.

It takes 1 calorie of heat to warm 1 gram of water 1 degree celcius (1.8 degrees F). It takes around 600 cal. of heat to convert that same gram of water into water vapor at the temperatures we operate our aquariums. My SPS tank can evaporate up to 4 gal. per day. That 4 gal. represents over 9 million calories of heat. So, you can see that this starts to get into some pretty staggering numbers by the time you are done.

I am not a physicist, but I did stay at a Holiday Inn Express last night.