The carbon peaking and carbon neutrality goals bring a rapid expansion of renewable energies, such as photovoltaic power and wind power. However, the output power of renewable energies is intermittent which may bring frequency deviation problems. The regulation ability of traditional generators may be insufficient to handle the frequency deviations since the great scale of renewable energies is replacing traditional power generators. With the development of communication technologies, demand response acquires more attention. Heating, ventilation, and air-conditioning (HVAC) systems are suitable for demand response because they occupy a large portion of energy consumption and have huge regulation potential. Moreover, HVAC systems' power consumption is flexible and adjustable by using the thermal storage feature of the buildings. When turning off the air conditioner or adjusting the set temperature, customers' comfortable indoor temperatures can be maintained. However, considering the complexity and large scale of the power system, most previous studies on HVACs' frequency regulation are verified only by simulation tools, e.g., MATLAB and Simulink. This study investigates the hardware-in-the-loop (HIL) towards frequency regulation service by HVACs with RTDS. The HIL platform is implemented in the case of frequency regulation in a high photovoltaic power penetrated campus grid. The scenario is designed with a building thermal model based on the quantized architecture characteristic parameter which is considered the part of HVAC operation model.