Usually, when a regulator imposes a constraint, it's up to the constrained party to (figure out how to) gather the intelligence required to follow the constraint.

It may turn out that there are other regulations (e.g. privacy regulations) preventing a company from gathering that information about individuals, though. At which point the power company would probably have to stop selling to individuals altogether (i.e. provide no residential power service any more, just private commercial/industrial service to other companies, because companies have a lot fewer privacy protections so it's easy enough to figure out whether they're mining.)

maybe it's obvious relatively to the history of a plan. if one residential building takes N times more than others 24/7 you can assume mining