Operating cost comparison of state-of-the-art heat pumps in residential buildings across the United States

Abstract

With increasing concerns about the long-term global warming effect of HFC refrigerants, low-GWP refrigerants and non-vapor compression heat pumps are gaining attention to be the replacements for current vapor compression heat pumps that rely on HFCs. In addition, advanced heat pump solutions, such as heat pump water heaters, cold climate heat pumps, and low-GWP heat pumps are emphasized by regulators to make the heat pump market cleaner, more efficient, and more affordable. However, current research efforts lack comparisons of the new technologies under realistic building loads, climate conditions, and utility rates. In addition, combinations of emerging technologies have also not been considered. This study developed a methodology to systematically evaluate conventional and emerging space conditioning and water heating technologies both from performance and operating costs points of view. This study analyzed eight HVAC configurations for space heating, cooling, and water heating in terms of annual operating cost when coupled with an actual building affected by weather conditions. The eight HVAC configurations covered advanced solutions such as heat pump water heaters, ground source heat pumps, cold climate heat pumps, and membrane heat pumps, and they were compared with traditional vapor compression heat pumps and gas furnaces. The operating cost assessment was conducted based on building energy simulation using the real utility structure. The results revealed the trade-offs between HVAC combinations for the eleven climate zone covered in this study. The two-stage cold climate heat pump can save 10%–20% heating costs than single-stage heat pumps in cold regions. A membrane evaporative cooler can provide cooling cost savings in eight out of the eleven climate zones analyzed. A gas furnace should only be used in cold places where the electricity price per kWh to gas price ratio is higher than 3. HPWH should be recommended to places where the electricity price to gas price ratio is below 3.