VRF systems are considered either a heat pump system or a heat recovery system, which can heat and cool simultaneously. VRF systems obtain their high efficiency through the use of inverter compressors. Inverter systems allow the compressor to ramp up or down based on the needs within each space.

Central AC systems are known for their energy efficiency, ease of temperature control, and ability to handle high cooling loads, making them suitable for larger commercial spaces.

Air-to-water heat pumps work by circulating heated water through radiators or underfloor heating systems in a home. Unlike mini-splits, which use refrigerant, these systems transfer heat from the outside air to water that circulates within the building.

This type of air-to-water heat pump is called a "split system" heat-pump water heater; it is designed to extract heat from outdoor air rather than indoor air. The main advantage of locating the compressor outdoors is that these water heaters don’t lower the temperature of the indoor air during the winter.