Advocates call electric cars a solution to combat global warming, critics have suggested coal-fed grids make them dirtier than conventional cars, but critics have the right to be wrong.

The question is over well-to-wheel greenhouse gas (GHG) emissions and the short answer is electric vehicles (EVs) are cleaner; it’s only a matter of how much over an internal combustion engine (ICE).

True enough an all-electric car like a Nissan Leaf does have “upstream” GHG emissions, including carbon dioxide, methane, and nitrous oxide, but gas-powered vehicles are responsible for emissions at the tailpipe that an EV does not have and upstream as well.

This may not always occur to people who’ve read the studies siding with the incumbent technology, but gasoline is not like spring water that bubbles out of the ground into the pump. Rather, oil companies spend billions exploring, extracting, refining, and transporting it and that means upstream emissions which the U.S. EPA reports even if others forget to.

Electric Cars Are Always Greener Than Gas

Sometimes it is a close call whether an EV makes sense, and the Union of Concerned Scientists concedes as much.

But even under a worse-case scenario, typical EVs still beat the upstream-plus-downstream emissions from an average gas car sold in the U.S. by 40 percent according to the EPA.

EPA numbers are averaged between sources including hydroelectric, nuclear, natural gas, coal, wind. Renewable energy is cleaner, and cleanest is home charging with renewable energy. The mix of "grid" energy ranges from dirtier to extremely low-emission.

EPA numbers are averaged between sources including hydroelectric, nuclear, natural gas, coal, solar, wind. Renewable energy is cleaner, and cleanest is home charging with renewable energy. The mix of “grid” energy ranges from dirtier to extremely low-emission. Among its overlapping info sources, the EPA has this Power Profiler that lets you check your area by zip code.

Take, for example, Denver, Colorado. It’s in the “RMPA” grid region which averages out as the country’s highest in GHG. There a “zero-emission” Nissan Leaf’s electricity is responsible for 290 g/mile of CO2, more than double Southern California’s 120 g/mile and 100 g/mile more than the Leaf’s 190 g/mile national average.

That’s not so great, but it still beats the nationwide 480 g/mile of an average new conventional car’s upstream-plus-tailpipe emissions and the Leaf even edges out a 33-mpg Honda Civic the EPA says nets 330 g/mile anywhere in the country.

Dirty Fossil Fuels

Fossil fuels in the U.S. come from numerous sources, including imported, domestic hydraulic fracturing and conventional wells, offshore wells, and Canadian oil sands.

According to the UCS’ David Reichmuth, senior engineer, Clean Vehicles Program, outside of California it’s unclear state by state where gasoline or diesel at the pump may have originated from. Refineries take in the oil coming from different origins and blend it, so while there are variances in upstream GHG, the EPA lumps it all into one averaged number on

Canadian oil sands site.

Canadian oil sands site.

Another federal source, Argonne National Laboratory, is working on analyzing the fuel mix further, along with related questions, but meanwhile a study it reported last month raises concern over the petroleum mix in the U.S.

Specifically, fuel extracted and refined from Canadian oil sands release approximately 20 percent more carbon into the atmosphere over its lifetime than fuel from conventional domestic crude sources, says Argonne.

“This is important information about the greenhouse gas impact of this oil source, and this is the first time it has been made available at this level of fidelity,” said Hao Cai, the Argonne researcher who led the study. “Canadian oil sands accounted for about nine percent of the total crude processed in U.S. refineries in 2013, but that percentage is projected to rise to 14 percent in 2020.”

So while the U.S. electricity grid is on course to get cleaner, and has been getting cleaner, this federal lab says Americans will be feeding more dirty energy into their petroleum mix if they continue to live like they have become accustomed to.

Another source which U.S. oil interests proclaim as a victory for “energy independence” is hydraulic fracturing. Most-recent data released 2013 from the U.S. Energy Information Agency indicates new extraction methods as of 2011 also raise concerns. Among gases coming out from these advanced extraction methods are methane, a greenhouse gas 21-times more potent than CO2.

The highest emissions came from the San Juan Basin in New Mexico and the Permian Basin in Texas. Here horizontal drilling and fracking have led to a boom in shale gas and shale oil production.


Unraveling this GHG question further, it should be noted the worst offender by far is not the oil and gas industry, it is the electricity production sector.

That’s right, electric cars that plug in do so to a grid that collectively emits 10-times the GHG that the second-highest GHG-emitting oil and natural gas sector does – but it does not effectively matter.

Coal power. There is no grid in the U.S. that is 100-percent coal powered.

Coal power.

Why? Because electric cars are vastly more efficient and use less energy to travel farther than internal combustion counterparts.


According to the EPA, EVs convert around 59–62 percent of their electrical energy from the grid to turn the wheels versus gasoline vehicles’ sending to the wheels only about 17–21 percent of the energy stored in gasoline.

The EPA lets you drill down on emissions by zip code with this calculator, and ICE emissions are seen on fuel's car finder.

The EPA lets you drill down on emissions by zip code with this calculator, and ICE emissions are seen on fuel’s car finder.

This is why the “miles per gallon equivalent” of a Leaf is 114 MPGe combined, or four-times more efficient than a typical 28 mpg compact car.

An EV is so efficient, it needs only the energy required to heat a toaster oven 20 minutes to drive a 3,000 pound car one mile down the road.

Only Getting Better

The U.S. EPA is holding both the electrical sector and oil and gas industry to account in its agenda to curtail GHG

While some questions are still open about the future GHG profile from the oil and gas industry now squeezing the Earth for oil by advanced methods, internal combustion cars are getting more efficient, but so are EVs.

Source: Union of Concerned Scientists.

Source: Union of Concerned Scientists.

In a September 2014 update to a 2012 nationwide analysis of data from the U.S. EPA and Argonne National Laboratory, the Union of Concerned Scientists reiterated its endorsement for EVs to those who care about global warming.

Three years ago, the UCS’ State of Charge data showed 45 percent of Americans lived in the “best regions” for EVs, and by 2014 that number had risen

“Sixty percent of Americans now live in regions where an EV produces fewer global warming emissions than even the most efficient gasoline-hybrid vehicle,” wrote Don Anair Research and Deputy Director, UCS Clean Vehicles Program.

SEE ALSO: America’s Lowest Carbon Footprint Cars

That speaks to the grid, but Anair also noted EVs have gotten more efficient too since the UCS initial analysis.

“That analysis was based on the efficiency of the average BEV sold in 2011, equivalent to the model year 2011 Nissan Leaf (.34 kWh/mile),” said Anair. “With new EV models and upgrades to older ones, the current average efficiency of new BEV’s is .325 kWh/mile (based on sales from July 2013 to June 2014) – representing about a 5 percent improvement since 2011.”

Unaccounted for Variables

This report has used averaged numbers from the EPA but in reality life is not averaged, but specific. Both the fossil fuels consumed across the country and the electricity powering the nation’s grids come from a multitude of sources.

Just as petroleum GHG emissions vary across the country, electricity’s GHG also varies even within the same grid region with regards to potential contributing sources, such as hydro, nuclear, natural gas, coal, wind, solar, etc.

The BMW i3 is the most efficient EV sold in the U.S.

The 124 MPGe BMW i3 is the most efficient EV sold in the U.S.

A product such as the eMotorWerks Juicebox can monitor power plants or types of power plants in real time, writes the UCS’ Rachael Nealer, engineer and Kendall Science Fellow, allowing EVs to charge when more renewables are producing electricity.

This she calls a “game changer” but perhaps it is only a game refiner.

First generation EVs do hands-down beat conventional vehicles, and when next-generation EVs such as the Chevy Bolt, Tesla Model 3, and next Nissan Leaf come along, for many more now holding onto the ICE, it could be game over.