A power optimization method of deriving gated circuitry in a synthesized netlist of an integrated circuit (IC) design is provided. A block in the synthesized netlist is identified as an idle candidate block. Sub-blocks on the chip are clustered into a cluster. For the cluster, a clock gating structure optimized for power savings is determined, based on the idle candidate block. One or more inflexible clock gates are inserted in the netlist according to the clock gate structure.