Well, we've not yet installed any sort of climate control in the new house, and we've done fine for the week we've been in.
This is remarkable because we're in the Deep South, but we did plan in high thermal mass for stability and to take advantage of both natural heating and cooling when we designed the house, and we calculated the sun angles to be sure we got heat input in winter, not summer (and built among hardwoods for shade so we shouldn't overheat in October).
So far, so good. We haven't gone over 75 in the house in the middle of the afternoon, and that's with temps near 90 and one room open while the dogs learn about their new dog door. Oh, and at least for today, pumping heat inside the house with a dehumidifier --the dryer's also not installed, and it's hard to line dry in the rain, and I had to get one load done so I can go to work tomorrow. I'd have planned ahead and done it sooner, only we just moved the washing machine last night...