Methods, systems, and computer-readable media are described herein. One method embodiment includes determining an unscaled efficiency signal of combustion equipment using data measured from the combustion equipment, determining a theoretical efficiency signal of the combustion equipment using a theoretical efficiency surface of the combustion equipment and a subset of the measured data, and normalizing the unscaled efficiency signal using values from a correlated portion of the theoretical efficiency signal to monitor efficiency of the combustion equipment. Other embodiments can include providing a performance indicator of the combustion equipment in response to an operational mode change.