That's not very unusual. 240 is the "nominal". There is always some variation allowed, and actually most utilities intentionally try to have it a few volts higher, because they need to account for some transmission loss through lines and neighborhoods and connections, and then your house wiring, etc. My house has always run about 245V without heavy load on it. Once the charging current ramps up higher it drops by a few, but is still just a little over 240. And if you read the specifications on most types of devices, they will talk about acceptable voltage ranges and usually say something like 100V-250V if it's dual voltage for 120/240 use or if you look on a 14-50 outlet, it will say "250V".