A home energy management (HEM) system has the potential to enable demand response (DR) implementation for residential customers. This paper presents a detailed hardware architecture that allows control of an air conditioning (AC) unit by varying the thermostat set point. This can be accomplished by controlling a Wi-Fi enabled thermostat via an HEM system. The hardware demonstration of the proposed architecture is also discussed. This work showcases the applicability of the HEM system in managing an AC unit through a smart thermostat control. This approach can serve as an alternative to allowing an electric utility to perform remote disconnect to AC units. Controlling an AC unit by adjusting the thermostat set point can ensure lower average power consumption of the AC unit during a demand response period, along with better temperature control and improved equipment lifetime.