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They only look like conspicuous polluters.

A new breed of electric performance cars can keep pace with or even outperform the likes of a Lamborghini. The new models, including Porsche's Taycan and the Tesla Model S P100D, show how environmentally minded fans of horsepower might square their circles.

The Tesla Model S can sprint to 60 miles per hour in slightly more than two seconds, making it one of the quickest machines on the market. The Taycan, according to Car and Driver magazine, is rated even quicker.

But there's more to the story than just their speed. Even though they look like they would have a carbon footprint to rival that of a jet engine, they actually are greener than some of the modest e-vehicles made just a few years ago.

Even small, less powerful electric vehicles haven't always been cleaner than the most efficient gas-powered autos. A 2012 report from the Union of Concerned Scientists found that the environmental benefits of subcompact, modestly powered electric cars like the Nissan Leaf depended on where they were charged.

At the time, many states still relied heavily on coal-fired plants for electricity, and the investigators found that when factoring in the emissions resulting from electricity generation in some areas, electrics were no cleaner than efficient gasoline-powered cars.

EV technology has advanced considerably since then, and electricity generation has shifted, as well.

The latest report from the Union of Concerned Scientists, in an article by David Reichmuth, its senior vehicles engineer, is much more optimistic than the one eight years ago.

After analyzing all emissions — including those from fossil fuel production, along with conventional vehicle tailpipe emissions and power plant emissions — the group found that the average electric vehicle in the United States was responsible for emission levels equivalent to those generated by a gasoline vehicle that gets 88 miles per gallon. (The acronym for this is MPGe, for miles per gallon equivalent.)

In areas where a lot of coal is still burned to make electricity, the number can fall to as low as 49 MPGe, but those areas are few and less densely populated than regions with clean power.

Powerful, not power hogs

But what about electric supercars like the Model S and Taycan? Because they produce mammoth horsepower, doesn't it follow that their emission levels are high as well?

"A very powerful electric performance automobile is less efficient than a hyper-efficient EV but still far cleaner than a comparably powerful car that burns gasoline," Reichmuth said. He added that a Model S driven in California, which has some of the nation's cleanest electrical power, can achieve 120 MPGe.

The numbers Reichmuth cited assume that the Model S is driven responsibly. Driving with the throttle wide open heats the Tesla's battery, triggering electronic safeguards that slow the vehicle. So it isn't going to take on gasoline rivals in an endurance race. But in short sprints against gas-powered cars, it is nearly unbeatable.

The Taycan, according to Car and Driver magazine, recorded 70 MPGe on a 300-mile trip at 75 miles per hour. No gasoline-powered high-performance car can be driven anywhere near as economically as the Tesla or Porsche electric.

When asked if electric cars are taxing the electrical grid, Reichmuth said, "A high-performance EV is not like an appliance" that is drawing power 24 hours a day. "Oftentimes, they are plugged in at night."

Consider, too, that charging stations are turning to renewable power sources like solar, in combination with a battery storage system. Tesla has promised that its Supercharger high-speed charger network eventually will be powered exclusively by renewable energy.