Study: Super-Efficient Piston Cars Could Match EVs on Greenhouse Gas Emissions

Piston-powered cars can be as green as all-electric vehicles—but only if they can deliver a global average fuel economy of more than 51 mpg, according to the University of Michigan Transportation Research Institute.

UMTRI researchers Michael Sivak and Brandon Schoettle say in a draft report that the exact number depends on how electricity is generated to charge the EVs. When the energy source is coal or oil, piston power reaches parity with EVs at a mere 29 mpg. But when power to charge EV batteries comes from carbonless sources such as wind farms or hydroelectric plants, conventional cars would need to average 2,500 mpg and 5,100 mpg, respectively, to be as “green” as EVs.

The global average for parity is 51.5 mpg, according to the report. Among developed car markets, the emission balance point ranges from 525 mpg for France, which generates roughly 70% of its electric power from nuclear powerplants, to 40 mpg for China, where most electricity is generated by coal-fired plants. The average for the U.S. is 55 mpg.

The UMTRI researchers arrived at their rankings for 143 countries by considering “well-to-wheel” costs for various types of energy sources calculated by the Union of Concerned Scientists. They compared that data with country-specific information from the International Energy Agency about the energy sources each country uses for generating electricity. The report does not calculate the energy involved in making the vehicles themselves.

The result is a lengthy table of fuel economy averages that piston-powered cars would need to achieve to match the emissions from electrical generating plants. Averages range from more than 5,000 mpg for Albania, which derives almost all its electric from hydropower, to less than 30 mpg for such coal-burning countries as Niger and Botswana.