Heat pump systems and methods for providing chilled/hot liquid for air-conditioning and domestic hot-water, are provided. The heat pump systems include a first heat exchanger, a second heat exchanger and a third heat exchanger (e.g., a hot-water heat exchanger) that share at least one expansion valve disposed at a downstream position of the hot-water heat exchanger. The at least one expansion valve is disposed between the hot-water heat exchanger and the first and second heat exchangers. The heat pump systems can provide six operation modes, including a cooling mode, a heating mode, a water-heating mode, a heat-recovery mode, a simultaneous heating and water heating mode, and a defrost mode.