Here in the Great White North, I've never had AC at home. The new house has it, though -- required by the developer, to keep house values up, or something. We'll probably make use of it too, given the lack of trees on the lot. But all of our windows can be opened, and that will remain our primary means of cooling at night.

Meanwhile, it was -25C outside the other day. The furnace was set for 17C (but not running), and the inside was a balmy 22F. Passive solar heating courtesy of the South windows.