An interlock arrangement allows a floating neutral electrical generator having a receptacle, such as a duplex receptacle, absent GFCI protection to be used to provide electrical power to the electrical system of a home or other building during utility power interruption. The interlock arrangement includes structure to disable or prevent access to the duplex receptacle when the electrical generator is coupled to the power cord used to transfer electrical power from the generator to the electrical system of the building. Thus, the duplex receptacles cannot be used to power electrical devices when the generator is connected to supply power to the electrical system of the building. Conversely, when the generator is physically disconnected from the electrical system of the building, the interlock arrangement exposes or supplies power to the duplex receptacles, and may be configured to close access to the receptacle used for connecting to a building electrical system.