  Room-level air conditioners (also referred as ACs) consume a significant
proportion of total energy in residential and small-scale commercial buildings.
In a typical AC, occupants specify their comfort requirements by manually
setting the desired temperature on the thermostat. Though commercial
thermostats (such as Tado) provide basic energy-saving features, they neither
consider the influence of external factors (such as weather) to set the
thermostat temperature nor offer advanced features such as monitoring the
fitness level of AC. In this paper, we discuss grey-box modeling techniques to
enhance existing thermostats for energy-efficient control of the ACs and
provide actionable and corrective feedback to the users. Our study indicates
that the enhancements can reduce occupants' discomfort by 23% when maximising
the user experience, and reduce AC energy consumption by 26% during the
power-saving mode.
