Everyone is different as far as what temperature makes them the most comfortable, and comfort with temperature also differs with indoor and outdoor temperatures, so for example, someone may be comfortable with 85 degrees outside, but would be super uncomfortable with the same temperature inside! I asked some friends to see what temperature makes them turn their a/cs on in the summer, and the first person I asked was Paul. Paul lives in the south, where it is notoriously warm and humid, even before the Summer months. Paul said that as soon as it hits 75 degrees, his central air is turned on in his home, then he explained that it is more the humidity than the heat that motivates him to turn on the cooling system. Paul does not want the house getting that humid, moldy, uncomfortable feeling. He runs his central air until it cools down in the winter which does not always happen where he lives. I asked my neighbor Eri, who lives up north. Eri does not have a central air conditioner, because it is not necessary where she lives. Instead, she has several window a/c units- one in her dining room and one in the entryway. Eri said that she will usually turn on her window cooling system units when it gets up to 85 degrees or when it feels humid. It is possible for her to get comfort most of the Summer from windows being open and using a fan, instead of spending money on an air conditioner. It is absolutely fascinating how in different parts of the country, people have different opinions on when they feel it is necessary to use their air conditioner.