An assembly or adapter configured to provide a supply-side interconnect of electrical power to a distribution board. The adapter may be incorporated internal or external to the distribution board, by occupying the space of one or more circuit breakers, inserting an adapter into a meter termination socket, or the like. The adapter includes terminals provided to route the conductors from the utility to a breakout panel (or subpanel) for adding power devices as a supply side interconnect, and back to a regular route that may go through the meter and/or the main circuit breaker, and on to the loads. A switching component may provide an inline configuration that configures the conductors for backup function, and a parallel configuration that is a parallel interconnecting route when utility service is available.