It is hard this say what voltage is too low. For the water heater it means little. For the battery charging gear, you would have to check the nominal voltage operating . So too the television and microwave.
Low voltage to the AC often means higher current which usually is not good. But how much is too low.
As mentioned, the rest of the folks at the park went blissfully on their way, never knowing they had a problem.
Let's face it, on these hot summer days, with maximum loads on the utility companies, how many of us know or worry about how much the voltage drop is in our own homes.