Efficient energy usage inside buildings is a critical problem, particularly for high loads such as the Heating, Ventilation and Air Conditioning (HVAC) systems: over 30% of the global energy consumption resides in HVAC usage inside buildings. Usage awareness and efficient management of HVAC have the potential to significantly reduce related costs. Nevertheless, strict saving policies may contrast with users’ comfort. This paper proposes a Smart HVAC system where a trade-off between energy costs and thermal comfort of users is achieved. This user-centric approach takes advantage of the Social Internet of Things (SIoT) paradigm to augment real world objects with a virtual counterpart that leverages social consciousness to interact with other objects. Accordingly, a building thermal profile is characterized to drive the selection of the most appropriate working times for the HVAC. Experimental results prove that the implemented system is able to adapt to user’s needs and ensure an acceptable comfort level while at the same time reducing energy costs with reference to static or traditional scenarios.