Life cycle assessment of residential heating and cooling systems in four regions in the United States

Heating and cooling systems consume the most energy and are the largest source of emissions in the entire life cycle of a house. This study compares the life cycle impacts of three residential heating and cooling systems—warm-air furnace and air-conditioner, hot water boiler and air-conditioner, and air–air heat pump over a 35-year study period. Simulation and life cycle assessment studies of the systems at four locations in the United States, namely Minnesota, Oregon, Pennsylvania and Texas determine the effect of regional variations in climate, energy mix, and the standard building characteristics on the systems’ environmental impacts.In Minnesota, Pennsylvania, and Texas, the heat pump has the highest impacts whereas in Oregon the heat pump has the lowest impacts. A second scenario shows that substitution by high-efficiency equipment reduces the impacts of all systems but does not affect the order of relative performance by region. Another scenario examined the replacement of coal-generated electricity by renewable generation in regional grids. In order to reduce the impacts of the heat pump system to the lowest of the three systems, renewable sources would have to replace 42% of electricity generation in Minnesota, 15% in Pennsylvania, and 38% in Texas.