Abstract: Changing electrical power needs for buildings often requires the upgrade of the electrical panel, the addition of extra panels, or both. Herein, a single electrical panel hosts power interface modules that connect to multiple power rails within the panel. The modules, which plug into the panel, convert power between the rails, or make and break connections between the rails, under the command of a system controller. The rails are connected to switchgear to which a variety of external power sources and loads can be connected. The modules are cooled by a heat exchanger and the waste heat may be directed outside or used to heat inside the building or heat domestic water.