The smart meter is an emerging appliance which can be used to collect and monitor the power consumption data on electrical devices. Users can monitor these devices in order to adjust their operations for energy saving results. To avoid wasting power, it is important to set a power usage constraint to effectively monitor and control users' power consumption within a restricted power usage range. However, existing researches on smart-metering systems do not address this issue. In this study, a novel Intelligent Energy Saving (IES) system is proposed to effectively monitor and utilize the power usages of devices under the power consumption constraint. The IES system conducts context-based mining to discover device usage patterns and provide intelligent analysis of context-based usage behaviors, effective monitoring and utilization of power usages of devices for intelligent energy saving.