Like so many other home energy question, this is one without an easy answer.
Before I jump to answer the question with a resounding “Yes, feel free to set your thermostat low in the summer”, there is one critical question I have to know – do you have central air, or does the thermostat control a “climate control” system that has an air conditioner unit with it?
If your thermostat just controls a furnace, when the weather gets warmer, you can just turn off the furnace altogether (there should be a power …