And even if you "had AC" it typically wasn't central AC. Even when I was growing up in the 1970s our only AC was a window unit in my parents' bedroom. On hot summer nights we would go and sleep on their floor.

Residential units? Or does that include businesses too? Cause 12-15% for residential units sounds high for 1963.

Air conditioning was extremely uncommon in my neighborhood when I was growing up in the 80s. I didn't personally know a single family that had a/c until the 90s. The only places that were air conditioned in my neighborhood in the 80s were businesses. I'm sure it was more common in the South.