a thin - profiled gas cooler and chassis suitable for a transcritical heat pump water heater are provided . the heat pump system includes a chassis for supporting such system components as a gas cooler and evaporator . the dimensions of the gas cooler are designed to minimize the impact that the gas cooler has on the cooling capacity of the evaporator by reducing the amount of air flow that the gas cooler blocks . this is achieved by reducing the depth that the gas cooler extends into the chassis cavity . as a result , the height and / or width of the gas cooler is increased compared to other similar volume gas coolers is providing comparable water heating capacity .