Real-time scheduling based on dynamic voltage scaling (DVS) is an effective technique for reducing energy consumption in real-time embedded systems. Due to the dynamic nature and complex run time variations of such systems, DVS must be applied during run time to explore its utmost energy-saving potential. Despite this potential, an over-aggressive online scheme can actually increase energy consumption if practical processor limitations such as transition voltage and energy overhead are not considered carefully. In this paper we present an on-line scheduling algorithm called low power Limited Demand Analysis with Transition overhead (lpLDAT). It is the first algorithm in its class to explicitly account for transition overhead, and can reduce the energy consumption by as much as 40% when compared to previous methods.