Significant Fuel Savings and Emission Reductions by Improving Vehicle Air Conditioning

Vehicle air conditioning (A/C) systems significantly increase the fuel use and tailpipe emissions of automobiles. In addition, emissions of the A/C refrigerant are greenhouse gases. In 2002, the National Renewable Energy Laboratory (NREL) determined the U.S. national and state-by-state fuel use impact of air conditioning in light duty vehicles. In 2003, we expanded the analysis to cover Europeand Japan. With the assistance of the automotive climate control community, we have updated the analysis to include demisting, soak temperatures that vary with vehicle type, simplified clothing assumptions, and improved A/C compressor power definition. The updated NREL study shows that the United States uses 7.0 billion gallons (26.4 billion liters) of fuel a year for vehicle air conditioning,equivalent to 5.5% of the total national fuel use and 9.5% of the imported crude oil. If all vehicles had air conditioning, the EU would use 1.8 billion gallons (6.9 billion liters) of fuel per year or 3.2% of total vehicle fuel consumption. Japan would use 0.5 billion gallons (1.7 billion liters) or 3.4% of total vehicle fuel consumption. Converting the fuel consumption data into CO2 emissionsdetermines the indirect impact of air conditioning on the climate. We also determined the magnitude of the potential reduction in fuel use due to incremental improvements in A/C coefficient of performance (COP) over a baseline and the potential fuel saved per vehicle. For example, with a 25% improvement in A/C COP, a car in Arizona could save 15.7 gallons per year. These data highlight thepotential to reduce operational costs, A/C fuel use, and CO2 emissions by implementing advanced vehicle climate control technologies.