In this paper, we present an algorithm for the minimization of total power consumption via multiple VDD assignment, multiple VTH assignment, device sizing and stack forcing, while maintaining performance requirements. These four power reduction techniques are properly encoded in genetic algorithm and evaluated simultaneously. The overhead imposed by the insertion of level converters is also taken into account. The effectiveness of each power reduction mechanism is verified, as are the combinations of different approaches. Experimental results are given for a number of 65 nm benchmark circuits that span typical circuit topologies, including inverter chains, SRAM decoders, multiplier and a 32bit carry adders. From the experimental results, we show that the combination of four low power techniques is the effective way to achieve low power budget.