The invention relates to a monitoring apparatus for a steam plant, the apparatus comprising: a sensor unit (110) associated with a component of the steam plant, the sensor unit (110) being configured to provide an output indicative of the operating condition of the component; wherein the sensor unit (110) has a plurality of operating modes, each operating mode having a different resource usage; the apparatus further comprising: a selector (130) for selecting one of the plurality of operating modes; wherein the operating mode is chosen based on a current operating condition of the steam plant. The invention also relates to a method of operating such an apparatus.