Modern multicore microprocessors require attentive development to energy requirements when maximizing power-performance efficiency and ensuring reliable plus scalable functionality. IBM POWER9 relies on extensive modeling to identify representative workloads used when analyzing thermal design power and regulator design power against product requirements. Compounding benefits of circuit optimizations applied to the diverse subcomponents of the chip results in lower power cores, caches, and memory/IO interconnect. Specific dc- and ac-current analyses ensure proper definition of chip specifications for system voltage and current delivery. Finally, a systematic exploration of microbenchmarks on intermediate and final POWER9 hardware provides insight into processor core requirements while validating model accuracy.