An electrical panelboard enclosure includes an enclosure housing with an interior equipment chamber accessible by way of a service entrance door. A service panel is adapted for connection to a main power source in order to receive main power therefrom. A power supply is operatively connected to receive main power from the service panel and deliver it to a load. The power supply is also adapted for connection to a backup power source in order to receive backup power therefrom and deliver it to the load in the event of a main power cutoff. A load disconnector is operatively connected between the power supply and the load. The load disconnector is manually operable to disconnect the load from the power supply to prevent the power supply from delivering either main or backup power to the load.