HVAC is defined as heating, ventilation, and air conditioning. HVAC refers to the system that provides heating and cooling in both residential and commercial buildings.
HVAC systems are designed not only to heat but also to cool the air in a residential and commercial buildings, it allows moisture to escape by providing ventilation.
Mostly, AC units use electricity, not gas. On the other hand, HVAC systems use both gas and electricity. A gas HVAC system uses gas to heat an area while the air conditioner cools your home using electricity.