A hybrid multi-source system that is used to heat or cool a building. The system utilizes a heat pump or similar HVAC unit. A solar/air heat exchanger is provided. At least one ground heat exchanger is utilized. A plumbing network interconnects the heat pump, the solar/air heat exchanger, and the ground heat exchanger. A heat transfer fluid circulates through the plumbing network. Temperature sensors are used to monitor temperatures of the heat transfer fluid at multiple points in the system. At least one pump circulates the heat transfer fluid through the plumbing network. Valves are disposed within the plumbing network that can selectively isolate the heat pump, the solar/air heat exchanger, and the ground heat exchanger. A systems controller is coupled to the temperature sensors, the valves, and pump. The system operates in multiple modes which allow for higher efficiency and long term underground thermal storage.