Garage maybe? My house in Texas had the water heater and breaker box out there. Just a suggestion... Generally, your main dwelling breaker/fuse panels are inside. The exception being the main cut-off/breaker for an AC unit or pool heater/pump.
No garage. That would have been the first place I looked. I’ve missed it, somehow, but as I said, I just wanted to make sure he had access to it without wasting a lot of time moving things around to get to it. Boxes full of books are heavy!!