We address the issue of power efficiency at a relatively high level of abstraction -- tasks allocated on server systems. The domain is that of requests/tasks being forwarded to clusters of servers in data centers. We target the power delivery mechanism -- specifically, the power supply unit, and suggest techniques to distribute workload in a way that the total power is reduced by factoring this important parameter. We formulate the overall power minimization as an optimization problem that takes into account the variation of compute power and power supply efficiency with workload. Our proposed heuristic gives results that are close to that returned by standard NLP solvers, but takes a fraction of the execution time, making it a powerful alternative in a practical online workload distribution strategy.