Regulating Automobile Air Conditioning Efficiency Can Save Megatons of CO 2 Emissions for Free

Improving fuel efficiency for on-road vehicles is crucial to reducing the environmental impacts of the transport sector. However, fuel efficiency is regulated based on laboratory tests that usually do not consider the performance of on-board air conditioning systems. Therefore, car manufacturers are not fully incentivized to improve the efficiency of air conditioning. By analyzing one million real-world fuel efficiency records from Chinese light-duty passenger vehicle drivers, we show that gasoline consumption increases by 1.3% annually due to air conditioning use at higher temperatures. This response differs across car models with models produced by Chinese manufacturers showing the lowest efficiency. We estimate that regulating air conditioning efficiency could save 1.6 million tons of CO2 emissions annually for light-duty passenger vehicles in China, and this potential is essentially free to achieve. We suggest that expanding the regulation to more vehicle categories in more countries will further increase the saving potential substantially.