Revision with unchanged content. Microelectronic systems have advanced significantly in the recent years due to increased integration of circuits. The power consumption of such systems remains one of the greatest challenges however. Progressively more silicon and system resources are invested in new power management modes to enable acceptable system temperature levels, and sufficient battery life for mobile users. We describe a new power management methodology that makes use of energy scavenging techniques to deliver «green» microelectronic systems. This work and the questions it addresses are very relevant to our times when global warming is a bigger concern than ever, and yet most of us own increasing numbers of capable microelectronic systems to make life easier. Some of these questions challenge the metrics commonly used in the industry. Others encourage us to walk away from the system design misconception that useful energy to a microelectronic system is only available at the AC power outlet. The presented design metrics, multidisciplinary methods, tools, and concepts can be extended to many microelectronic systems, and are not typically offered in any one degree curriculum.