The definition of a small HVAC system is one that is designed to provide climate control to a smaller area, such as a single room or a small apartment. These systems are usually smaller in size and capacity than the larger HVAC systems used in commercial and industrial buildings. Small HVAC systems are typically designed to provide a single source of climate control, such as heating, cooling, or ventilation. They are usually powered by electricity, natural gas, or propane, and they can be either wall-mounted or floor-mounted. Small HVAC systems are usually more energy-efficient than larger systems, as they are designed to use less energy to achieve the same results. They are also more cost-effective, as they are typically cheaper to install and maintain than larger systems.