Smart heating controls are being introduced in the domestic sector with the aim of reducing heating demand in buildings. However, the impact of controls on heat demand is not fully understood. This study set out to add empirical evidence to Kempton’s theory on mental models of home heat controls. With this purpose, radiator setpoint records from smart thermostatic valves in 47 flats from a care home in the South of England were evaluated over a 12-month period. Three types of households were identified: (i) low interactors who do not have interaction, or have minimal interaction, with the controls (24.5%); (ii) medium interactors who adjust their setpoint when the outdoor temperature changes and whose behavior is comparable to households that have a “feedback” mental model (49%); and (iii) high interactors who adjust the setpoint based on their own strategy, which does not necessarily follow outdoor temperature changes and reflects a lack of understanding of how the controls work (26.5%). These results highlight the contrast between expected and actual usage of home heat controls, as only half of the residents showed a behavior that is consistent with the principles of operation of the STVs.