This paper aims to research the energy performance comparison of two types of HVAC systems for subtropical regions. Two HVAC models are simulated using DesignBuilder: (1) non-renewable energy source (non-RES) based HVAC system and (2) renewable energy source (RES) based grid-tied HVAC system. For simplicity of design, a three-story university building with multiple zones was built and the Bangladeshi weather condition was used for the simulation. The boiler and chiller are fueled by electricity and natural gas in a non-RES based HVAC model. Solar PV is installed on the rooftop of the university building as part of the RES based HVAC design, while ground source heat pumps (GSHP) are employed to only supply heating. This study also demonstrates that RES based HVAC models are preferable to non-RES based models because it reduces the need for natural gas, which really is limited in current world and produces greater CO2. Solar PV essentially lessens reliance on grid-fed electricity, which is essentially powered by natural gas. The RES based HVAC model is the most sustainable and appropriate choice for subtropical climate conditions also because of adequate renewable energy resources which apparently have a fixed cost but no variable or (operation and maintenance) O&M cost. Additional research in this work demonstrates that, in the case of RES based design, photovoltaic-fed electricity can partially meet the cooling requirement, which is higher than the heating demand. In essence, the comparison analysis confirms that RES is preferable to non-RES design.