 In addition, electric cars are becoming more efficient.For example, the Nissan Leaf and the Chevrolet Volt, have undergone improvements to increase their efficiencies compared to the original models launched in 2010, and other even more efficient BEV models, such as the most lightweight and efficient BMW i3, have entered the market.One criticism to the UCS analysis and several other that have analyze the benefits of PEVs is that these analysis were made using average emissions rates across regions instead of marginal generation at different times of the day.