What is the ruling on using electricity in one's parents' home if they are cheating the electricity meter, and what is one's duty towards them?

It is not permissible to tamper with the electricity meter or to defraud in order to evade paying consumption fees. Benefiting from mixed utilities is subject to the same ruling as dealing with owners of mixed funds, which is disliked (makrooh) but not forbidden (haram). Using electrical appliances connected to these meters is disliked. There is no blame on the questioner for obeying his parents in using electricity for their needs. Avoiding food prepared with this electricity is more pious and cautious, but it is not forbidden; it is permissible in itself. The fact that the family pays a portion of the electricity cost makes it disliked, not forbidden. This evil must be condemned, and whatever can be avoided of things that use electricity should be avoided, for Allah Almighty says: "So fear Allah as much as you are able."