According to one aspect, embodiments of the invention provide a method of operating a UPS system having a plurality of UPS's, the method comprising powering on the UPS system, assigning each one of the plurality of UPS's a unique identifier, calculating a master priority index for each one of the plurality of UPS's based on the unique identifier of each one of the plurality of UPS's, and based on the master priority index of each one of the plurality of UPS's, configuring each one of the plurality of UPS's to operate in one of a master mode of operation and a controlled mode of operation.