Virtualization allows multiple applications to run on different execution platforms, but sharing the same host machine. A better knowledge of the expected power consumption of computer hosts that run virtualized applications could help to improve capacity planning and optimization of cloud systems that use virtualization for resource management. In this paper, power and performance predictions are estimated from utilization figures of the main computer subsystems (CPU cores, drives, memory, and network ports), which handle the aggregated tasks produced by the virtualized applications. Extensive measurements conducted on two different systems validate the model. © 2011 IEEE.