A client looking to save money on energy expenses replaced their conventional thermostat with a smart one. The goal was to reduce energy bills by making efficiency gains. When significant reduction in energy expenditure failed to materialize, the client reached out to Midnight Mechanism for analysis from first principles. An overview of the client’s system immediately follows. Overview An acceptable indoor temperature range of 62°F to 77°F was established, with an optimum setpoint of 68°F.