An improved heat pump water heater of the type having a water tank with an exterior surface and defining a water chamber, a top on the water tank with at least one opening therethrough in communication with the water chamber, and a heat pump of the type having a compressor, the compressor being in fluid communication with an annular condenser assembly via a first refrigerant conduit, the annular condenser assembly being in fluid communication with an expansion device through a second refrigerant conduit, the expansion device being in fluid communication with an evaporator through a third refrigerant conduit, the evaporator being in fluid communication with the compressor through a fourth refrigerant conduit and control means therefore, the improvement comprising disposing the annular condenser assembly through the opening in the top of the water tank and into the water chamber, the water tank opening further comprising a geometric twisted sleeve positioned to form a helical insertion pattern in the annular condenser assembly, the annular condenser assembly further comprising an elongate outer tube having a closed bottom end and an open and opposed upper end in flow communication with the first refrigerant conduit, an elongate return tube disposed within the outer tube and having an open bottom end and a closed and opposed top end in flow communication with the second refrigerant conduit, an elongate capillary tube disposed within the return tube and having an open bottom end and an open and opposed top end in flow communication with the second refrigerant conduit, and an air gap disposed between the capillary tube and the return tube.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
 This invention was made with United States Government support under Contract No. DE-AC05-00OR22725 between the United States Department of Energy and U. T. Battelle, LLC. The United States Government has certain rights in this invention.