We present an energy-reduction strategy for applications which are resilient, i. e. can tolerate occasional errors, based on an adaptive voltage control. The voltage is lowered, possibly beyond the safe-operation region, as long as no errors are observed, and raised again when the severity of the detected errors exceeds a threshold. Due to the resilient nature of the applications, lightweight error detection logic is sufficient for operation, and no expensive error recovery circuitry is required. On a hardware block implementing texture decompression, we observe 25% to 30% energy reduction at negligible quality loss (compared to the error introduced by the lossy compression algorithm). We investigate the strategy's performance under temperature and process variations and different assumptions on voltage-control circuitry. The strategy automatically chooses the lowest appropriate voltage, and thus the largest energy reduction, for each individual manufactured instance of the circuit.