Abstract: A multiplex electrical outlet receptacle comprises a housing containing four or more receptacle outlets. The housing contains at least one tab extending from the top of the housing and at least one tab extending from the bottom of the housing to permanently secure the housing to an in-wall electrical box. A single electrical cable connection on the housing connects each of the four or more electrical receptacle outlets to a power source. The housing of the multiplex electrical outlet receptacle includes internal wiring and/or buses to connect each of the outlets in common to the electrical cable. Additionally, a two-sided multiplex receptacle and a corresponding electrical box are configured to provide electrical outlets to both sides of a wall. Additionally, a multi-receptacle plug-in adapter configured to allow more than one transformer type plug to connect to the adapter at the same time.