Abstract For transiently powered systems a reliable power management is essential. Power management methods in software allow for run-time decisions about the utilization of system resources based on energy models, performance counters and sensor readings. However, finding precise energy models for peripheral devices can become a tedious and challenging task, as they are subject to hardware/software interactions and complex hardware behavior, often with unknown energy characteristics. In this paper, we tackle these problems for a broad set of cases by creating an automated measurement loop for deriving precise energy costs of driver function calls and their parameters. This becomes possible by using an automata-based modeling scheme, which can easily be implemented into the system software.