Why hybrids are more efficient in India, China than in the U.S.

Slow, congested traffic, aggressive driving and a lack of freeways is what makes travel in India and China difficult. But when it comes to hybrid vehicles, it's these types of conditions that actually improve fuel efficiency, according to a study by the U.S. Department of Energy's Lawrence Berkeley National Laboratory.

In two studies, which used real-world driving conditions, researchers found hybrid vehicles are significantly more fuel efficient in China and India than in the United States. 

In India, researchers simulated drive cycles in Delhi and Pune and used the modified Indian drive cycle, the test for the official fuel economy rating. In China, simulated drive cycles were conducted in 11 cities and with three powertrains—start-stop, parallel and power split. In both cases, researchers compared it to drive cycles used for U.S. fuel efficiency ratings, which include about 55 percent city driving and45 percent highway driving. 

Researchers found that driving a hybrid would achieve fuel savings of about 47 to 48 percent over a conventional car in India and about 53 to 55 percent in China. Meanwhile, in the U.S., hybrids are rated to produce a fuel savings of about 40 percent over their conventional counterparts.

Researchers found frequent starting and stopping, considerable amount of time spent idling, and low percentage of time spent on highways were the three ways hybrids save additional fuel.

The results could provide a catalyst for India to move more aggressively with national plan to have six to seven million hybrid and electric vehicles on the by 2020. The government is already working with the researchers to further analyze the results, according to Berkeley. 

India and China are members of the  Electric Vehicles Initiative (EVI) of the Clean Energy Ministerial, a forum of governments focused on accelerating the transition to clean energy technologies.