An energy storage system (ESS) provides redundant power feed support to a power system which provides secondary power support to a set of electrical loads, independently of a power system which provides primary power support. The power inlet connection of the power system can be switched between a utility power feed and a discharge feed from the ESS based on determinations regarding whether the utility feed is interrupted. The ESS and the power system can each be coupled to the utility power feed via separate breaker-supported power line connections, which themselves can be coupled via a breaker-supported branch circuit downstream of the power line connection breakers. The branch circuit breaker can be closed, to switch the power inlet connection from the utility power feed to the ESS, based at least in part upon a determination of a voltage difference across the branch circuit breaker.