This is according to the U.S. EPA’s fueleconomy.gov website which lets consumers determine tailpipe plus upstream emissions, and the difference on a nationally averaged basis is negligible, while regional variations see one car or the other pulling ahead.
To get terms clear: “tailpipe” emissions are self-explanatory, that’s a measure of CO2 from vehicle exhaust, and “upstream” emissions have to do with getting the energy to the vehicle. Since the Volt is a plug-in hybrid with 53 miles EV range, its 51 grams/mile tailpipe emissions are paltry as the engine is not running much of the time. However, its electricity, when coming from powerplant-fed grid energy – which varies by region – must be factored to arrive at a carbon footprint. Nationally, it’s estimated at 151 grams/mile with most of this being from electricity generation, and a tiny bit from the emissions generated to supply for the Volt’s gasoline. The EPA also figures 171 grams tailpipe emissions per mile for the Prius Liftback, and 34 grams/mile “upstream” emission figure for the gasoline used by the hybrid, based on nationally averaged numbers.
That said, going just by the simple online tool the government provides, the Volt averages 200 grams/mile and the Prius averages 205 grams/mile in total tailpipe plus upstream emissions.
Based on an assumed 15,000 miles per year, and 45 percent highway/55 percent city driving, the EPA says the Volt edges out the Prius by a mere 165 pounds of CO2 emitted per year in its imaginary textbook world.
When cars are measured in terms of tons of CO2 per year, 165 pounds is not a huge edge.
Of course no one lives in an imaginary world, and before anyone pounces on the EPA for being “misleading,” it does let consumers drill down by zip code to get a better grasp of the upstream emissions for plug-in electrified cars in their region.
In a place where more coal is used, such as Akron Ohio, a 205 gram/mile Prius emits less CO2 than a Volt, which the EPA estimates at 230 grams/mile.
If one lives, say, in Hartford, Conn., as noted by Mark Renburke, Executive Director, Drive Electric America, the Volt scores well with a cleaner 150 grams/mile while the Prius stays constant at an estimated 205 grams/mile.
A similar advantage is found in Long Beach, Calif., which has a cleaner grid in which the EPA says the Volt nets 140 grams/mile while the Prius stays constant at 205 – though cost of said energy may be another matter, but here we’re just looking at greenhouse emissions.
The takeaway, notes Renburke, is it all depends on where you live.
“If you live in California or Connecticut, the Volt is the clear lower emissions champ,” he says. “But if you live in Colorado or Kansas, the Prius edges it out with lower CO2 per mile driven. And if you live in Tennessee or some parts of Texas, it might just be a wash.”
According to the Union of Concerned Scientists, EVs – which the Volt essentially is, with extended range – produce fewer emissions in 70 percent of the country compared to a gasoline car that gets 50 miles to the gallon (the Prius gets 52-56).
“On average, today’s electric vehicles are as clean as gasoline cars that get 73 miles to the gallon,” says the UCS whose updated stats map out greener and less green regions of the country assuming local grid energy.
Further, says Roland Hwang, director of the Natural Resources Defense Council’s Energy and Transportation Program, both the Volt and Prius are both great choices for the environment, but the Volt holds an edge.
“In many if not most places, Volt is clearly better due to the cleaner grid,” said Hwang, adding data should be viewed as a “snapshot” of an improving grid. As the EPA’s Clean Power Plan moves forward – either through courts or post Trump Administration, he observes, the powerplant sector will only improve.
“The key here is that oil production is only getting dirtier,” he said referring to oil sourced from tar sands and fracking, while power generation is only getting cleaner due to reduced coal reliance, and that renewables are the fastest-growing source.
Renburke likewise notes the grid is getting cleaner year by year, “so the Volt is passing the Prius with lower emissions in more and more states and regions.”
Beyond this, a host of other variables come into play as to which car is a better solution, but that they are represented as such is a fact.
When the Volt was released, it was often presented as out-Priusing the Prius, if the key metric was fuel and emission savings.
And the Volt’s fuel savings are without a doubt better in local driving, but there’s something to be said for the Prius whose engineers sought to make it their best fuel sipper to date.
Speaking of which, the Prius Prime should also be mentioned, which gets outstanding efficiency numbers, but seats only four, and has only 25 miles EV range, notes Renburke.
“There is a very, very narrow window where the Volt still barely beats the Prime by staying off gas altogether when the Prime can’t, and that’s something like if you drive between ~35 and 53 miles a day,” says Renburke. “That’s my commute, in the Prime I’d run out of battery two-thirds of the way to work!”
52 mpg versus 42 mpg
The Volt uses no gas for the first 53 miles on the combined test cycle, says the EPA, but afterwards it averages 42 mpg – which means a tad more emissions as well.
The Prius in most trims gets 52 mpg, so on longer journeys its advantages start to come into play. Typically a Volt driver, depending on how the drive goes, is still better on trips up to and over 100 miles, but this is a factor to be aware of.
Beating the Averages
As noted, nationally averaged numbers are only of some value, and local numbers are of better value, and then there’s the prospect of using the Volt for all it’s worth.
General Motors has noted OnStar data proves Volt drivers go over 900 miles on a tank full, so in their real world usage, they are mostly operating on electricity.
Also Voltstats.net has made it a game for Volt drivers to keep their cars in EV mode as much as possible, and data from that site indicates hundreds and even thousands of miles traveled with little or no gas use.
But that’s about gas, and coming back to emissions, the Volt, like any car, offers pros and cons, and even used as a pure EV, its carbon footprint remains.
When propelled purely by electricity, the EPA estimates a Volt is good for “106 MPGe” or 31 kWh/100 miles. Its pure electric footprint is still 149 grams/mile if one deducts the 51 grams/mile tailpipe emissions from the 200 national average.
This comparison, by the way applies to all plug-in cars. A 2017 Nissan Leaf, for example, which is more efficient at 112 MPGe or 30 kWh/100 miles, has 180 grams/mile upstream emissions according to the U.S. EPA. A Chevy Bolt – 119 MPGe or 28 kWh mile – is estimated at 170 grams/mile.
Local numbers in Long Beach for either gas-free car are just 100 grams/mile, but our example of in Akron, Ohio, they’re at 200 grams/mile or right there with the Volt on a national basis, and only a wee bit behind the Prius at 205.
EVs Still Win
The above said, the UCS maintains EVs are still superior in most of the country in its a cradle-to-grave analysis.
“Over their whole life cycle—from manufacturing to driving to disposal—electric vehicles produce half the emissions of a comparable gasoline vehicle,” says the UCS. “By far the largest share of emissions comes from driving, which is where electric vehicles have a big and growing advantage.”
The UCS also has an interactive online tool that lets drivers learn how clean different plug-in vehicles are where they live, as well as a map showing how electric vehicle emissions compare across the country.
While the Volt – or other EVs – may emit more tailpipe plus upstream emissions in some regions than a 52-mpg Prius, this is of course not the only reason why someone buys a car.
“The Volt and Prius are not comparable in performance,” says Renburke. “The Volt performs very similar to an upscale V6 sedan while the Prius is still clearly in econo-car territory. So when they are at break-even at least in emissions, the Volt still has that advantage simply as a driver’s car.”
Beyond that, a total cost of ownership analysis comes into play, as does which car simply suits your sensibilities and personal needs the best.
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