Abstract
We evaluate energy consumption under unknown service demands using three policies: task assignment based on guessing size (TAGS), the shortest queue strategy and random allocation in a homogeneous environment. We modelled these policies using performance evaluation processing algebra (PEPA) to derive numerical solutions. Our results show that servers running under TAGS consumes more energy than other policies in terms of total energy consumption. In contrast, TAGS consumes less energy than random allocation in terms of energy per job when the arrival rate is high and the job size is variable.