There are several different types of residential heating, ventilation, and air conditioning (HVAC) systems, and the most efficient system for a particular home or building will depend on a number of factors, including the size and layout of the space, the local climate, and the specific needs and preferences of the homeowner.

That being said, some of the most efficient residential HVAC systems include:

1. Geothermal heat pumps: Geothermal heat pumps use the constant temperature of the earth to heat and cool a building, and are typically more energy efficient than traditional air-source heat pumps.
2. Ductless mini-split systems: Ductless mini-split systems consist of an outdoor unit that is connected to one or more indoor units by a small, flexible refrigerant line. They are typically more energy efficient than traditional central air conditioning systems because they do not require ductwork, which can be a significant source of energy loss.
3. Variable speed motors: Many HVAC systems use motors that operate at a single speed, but variable speed motors can adjust their speed based on the cooling or heating demand of the building. This can help to improve energy efficiency and comfort.
4. Inverter-driven compressors: Inverter-driven compressors are used in some air conditioning systems to adjust the speed of the compressor based on the cooling demand of the building. This can help to improve energy efficiency and comfort.

It is important to note that the most efficient HVAC system for a particular home or building will depend on a variety of factors, and it is always a good idea to consult with a qualified HVAC professional to determine the best system for your specific needs.