> My grandparents keep their central AC on in the mid 80s…
I always would set my AC to 78 during the Phoenix summers, the difference between that and the outside temperature was enough to keep me happy. I’d also have to mostly avoid businesses that kept it to a more “comfortable” temperature because I’d get cold and I don’t like being cold…which is the main reason (behind the electric bill) for my choice, I absolutely refused to pay to be cold.
I remember I was carted down to the basement of the VA hospital to get X-rays during the summer and I was literally shivering the whole time I was down there, they probably had it set to something reasonable like 72.
—edit—
To answer the actual question, I talked to old people who grew up in Phoenix and they said it wasn’t all that bad back in the day. The heat island makes a big difference and there was a lot more agriculture surrounding the city keeping the temperature down.