Safety in Numbers
Brighter Planet's blog
Prius vs. Volt Reprise
Following the surge in sales of the Chevy Volt in March, we thought it could be interesting to revisit our post from August 2009 comparing the greenhouse gas emissions of the Volt to the Toyota Prius.
Sneak peak: the Prius still rules in most of the US.
The EPA rates the 2012 Chevy Volt at 97 miles per gallon equivalent (36 kilowatt hours per 100 miles) when running on electricity alone, or 60 miles per gallon for a combination of electric- and gasoline-powered driving. That handily beats the 2012 Toyota Prius’ 50 miles per gallon. And yet the Prius is still the greener option for two thirds of Americans.
How can this be? When running on electricity the Volt doesn’t eliminate emissions, it just shifts them from its tailpipe to a power plant smokestack. And throughout much of the country electricity is more than twice as dirty as gasoline. This map shows where, based on the dirtiness of the power grid, it’s still better to drive a Prius. We’ve assumed the Volt operates in electric-only mode - the Prius would dominate even more if we compared mixed-mode driving.
Based on eGRID2010 v1.1 subregion emission factors
Our goal here isn’t to denigrate the Volt or plug-in hybrids in general. On the contrary we’re excited to see these vehicles entering the mainstream. In the long run electric cars will be cleaner than the most efficient hybrid imaginable, and they’re already the greener choice for anyone who generates their own power from renewable sources or has access to relatively clean grid electricity. Rather we want to emphasize the importance of shifting to cleaner electricity sources in tandem with our transition to efficient electric vehicles. Until we do, so-called “zero emissions vehicles” will remain anything but.
N.B.
To simplify the comparison, we’ve assumed that the emissions from manufacturing the Volt and Prius are equivalent and that the vehicles have similar lifetimes. We’ve also left out emissions from extracting, transporting, and processing raw fuels into electricity and gasoline. A rough comparison using Carnegie Mellon’s lifecycle assessment tool and EIA energy prices suggests that the embodied emissions of electricity are greater than those of gasoline, so including these would skew things even farther in the Prius’ favor.
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