Abstract: An energy system that couples or integrates an electrochemical converter, such as a fuel cell for the production of electricity, with a Heating, Ventilation and Cooling (HVAC) system, is disclosed. Waste heat generated by the fuel cell is radiatively, convectively, or conductively directed to a thermal component, such as a heat-actuated chiller or a boiler, of an HVAC system. The HVAC system receives the waste heat to produce a conditioned fluid, e.g. heated or cooled air or water, or steam, for heating, cooling, or industrial uses. The invention provides an improved efficiency energy system capable of providing electricity, heating and cooling, such as for a commercial facility or for residences. Also disclosed in an interface exchange element for convectively coupling an electrochemical converter to the HVAC system.