Prius still tops in green rankings among similarly sized cars

With the launch of the Chevy Volt and Nissan Leaf, the race along the green track is now fully joined for gasoline versus the grid.

In an earlier post, we saw the grid-powered Mini E outscore the “Austin Powered” Mini Cooper petrol edition in terms of green goodness. The respective eRatings are 199 for the Mini E and 120 for a Mini Cooper Hardtop. We won’t argue if you judge them a tie on the scale that really matters, namely, the cuteness factor.

The Chevy Volt’s eRating of 161 puts the plug-in hybrid easily ahead of most cars. The all-electric Nissan Leaf’s eRating of 195 moves it beyond the reach of the most fuel-efficient internal combustion compacts and even subcompacts, which score in the 120-140 range.

2010 Toyota Prius

But what about grid-free hybrid drive? As it turns out, the Toyota Prius gets an AutoEcoRating of 205, putting it well ahead of the pack in terms of environmental friendliness.

Electric cars look great compared to ordinary gasoline cars. But in an apples-to-apples comparison that tallies pollution from the tailpipe to refineries and power plants and beyond, the eco-advantage of highly efficient hybrid drive, as epitomized by the Prius, still shines.

Here’s the back story. The AutoEcoRating system works from EPA-certified fuel economy and emissions numbers. On the fuel efficiency equation alone, the Chevy Volt is clearly a high roller in all-electric mode. Its 93 miles per gallon (MPG) gasoline equivalent rating tops the Prius combined average of 50 MPG and is right up there close to the Leaf’s 99 MPG equivalent.

But that high electric efficiency races into the upstream headwind of an electric power grid that remains half reliant on coal. Although power plants have been getting cleaner, they still spew a lot of pollution that results in both climate-cooking greenhouse gas and city-choking smog. The process of extracting, shipping and refining petroleum pollutes a lot, too. But its very high fuel economy makes the Prius much less responsible for those parts of the problem.

The Prius also sports a “partial zero emission vehicle” (PZEV) rating, meaning that the amount of smog-causing pollution from its tailpipe is nearly unmeasurable. Chevy is still working on PZEV status for the Volt, but for now the car is certified as an ultra-low emissions vehicle (ULEV). That’s quite clean, but not as clean as the Prius. The Leaf is of course a pure zero-emission vehicle (ZEV), but the hair-splitting difference between a PZEV and a ZEV isn’t enough to close the gap.

Finally, because AutoEcoRating also reflects the pollution from manufacturing a car and its components, the lower weight of the Prius, which is not nearly as battery-burdened as either the Leaf or Volt, helps out as well.

Add it all up and the Toyota Prius pollutes 5% less than the Nissan Leaf and 21% less than the Chevy Volt.

 

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