Power consumption is the greatest concern in current highly-integrated hardware-system design. The power reduction is targeted mostly through power management, implementing such techniques as clock gating, power gating, or voltage and frequency scaling. Due to growing complexity, the start-point in the design has moved from the register-transfer level to the system level. However, the power management lacks the abstraction needed for the system level. Also, different power-management techniques are specified differently, complicating the specification even more. This paper targets the unified specification of power-management techniques early in the design flow. SystemC is used for describing the system functionality along with the power management. Efficiency of the proposed approach is illustrated by comparison of the unified power-management specification and the standardized approach.