Hybrid Power Management for Office Equipment

Office machines (such as printers, scanners, facsimile machines, and copiers) can consume significant amounts of power. Most office machines have sleep modes to save power. Power management of these machines is usually timeout-based: a machine sleeps after being idle long enough. Setting the time-out duration can be difficult: if it is too long, the machine wastes power during idleness. If it is too short, the machine sleeps too soon and too often—the wake-up delay can significantly degrade productivity. Thus, power management is a tradeoff between saving energy and keeping response time short. Many power management policies have been published and one policy may outperform another in some scenarios. There is no definite conclusion regarding which policy is always better. This article describes two methods for office equipment power management. The first method adaptively reduces power based on a constraint of the wake-up delay. The second is a hybrid method with multiple candidate policies and it selects the most appropriate power management policy. Using 6 months of request traces from 18 different printers, we demonstrate that the hybrid policy outperforms individual policies. We also discover that power management based on business hours does not produce consistent energy savings.