In Norway we quite recently switched to more accurate networked meters and at that time they said that as much as 30% of all electricity produced wasn't accounted for, which you end up paying for, one way or another. Some of these losses are from the network itself. But a not insignificant part was from people illegally tapping the grid or last-mile losses due to poorly maintained infrastructure that was hard to pinpoint without using expensive manpower to physically check every single connection.