CO2 emissions from electric vehicles in the USA in May 2021
2021-05-25. All-electric vehicles emit less greenhouse gases to the atmosphere than any other vehicle type in 44 of 50 states in the USA. There remain only six states where dominance of coal burning to generate electricity makes all-electric vehicles more polluting than hybrid electric vehicles: Indiana, Kentucky, Missouri, Utah, West Virgina and Wyoming.
Introduction
One of the main reasons explaining the rise in popularity of electric vehicles (EVs) is that they do not directly require the burning of fossil fuels to take us from point A to point B. In other words, EVs can potentially help us reduce CO2 emissions that are responsible for human-caused global warming.
However, if the power grid from which we charge EVs requires the burning of fossil fuels (coal, natural gas, oil) to generate electricity, are we better off in terms of CO2 emissions to the atmosphere? The answer to this question depends on where you live.
Online tool to estimate annual CO2 emissions
Using grid electricity is not always the only choice for EVs; a growing number of people install solar panels on their house’s roof and store excess energy in home battery storage systems. This enables them to recharge their electric cars with 100% renewable energy regardless of which state they live in. But for most people who rely on grid electricity, the U.S. Department of Energy’s Alternative Fuels Data Center has set up a website that compares an electric car’s well-to-wheel CO2 emissions relative to hybrid and conventional cars, using each state’s average electricity mix that often includes the burning of fossil fuels (coal, natural gas, oil). On this web page, the first thing we see are the national averages of annual CO2 emissions for four categories of vehicles:
- All-electric, also known as Battery Electric Vehicles (BEV)
- Plug-in hybrid electric vehicles (PHEV) that can be plugged for recharging at home or elsewhere but that can also extend their travel range by burning gasoline after the battery runs out of energy.
- Hybrid electric vehicles (HEV) that cannot be charged from the power grid but have an electric motor and a battery that recharges itself when we slow down, break, or go downhill.
- Conventional cars with internal combustion engines burning Gasoline.
On average across the USA, all-electric vehicles (BEV) emit the smallest amount of CO2 to the atmosphere. PHEV and HEV are close to each other with only a small advantage in favor of the PHEV. Conventional gasoline burning vehicles emit three times as much greenhouse gases to the atmosphere compared to all-electric vehicles, twice as much compared to PHEVs, and 83% more than HEVs.
But that’s a national average, and this does not tell us much about California, New Hampshire, or Illinois for example. All we need to do is click the “Choose a State” button, and this allows us to quickly find out if we live in a state where a BEV or PHEV emits less CO2 than an HEV or conventional vehicle. For brevity, the only two states whose results are presented here are those with the lowest and highest levels of CO2 emissions from electricity sources.
In Vermont, renewable forms of energy (hydro, biomass, wind, solar) are responsible for more than 99% of electricity generation. Consequently, well-to-wheel CO2 emissions (see definition at end of this post) for an all-electric car are zero in Vermont. Plug-in hybrids emit the second least amount of CO2. An HEV in Vermont emits about twice as much CO2 as a PHEV, and a conventional car emits 3.5 times as much CO2 as a PHEV.
In West Virginia, where 88.5% of electricity comes from coal burning, the vehicle type with the lowest carbon footprint is the HEV because it is never connected to this carbon-intensive power grid. One would need reasons other than reducing CO2 emissions, such as enjoying a silent drive or enjoying the exhilarating acceleration and low center of gravity of a BEV, to justify purchasing an all-electric vehicle in this state.
Maps of CO2 emissions rank by vehicle type
For each of the fifty states, we can find out what vehicle type emits the least amount of CO2 to the atmosphere, and determine what vehicle type finishes second, third and fourth in increasing order of CO2 emissions. The results are displayed in the four maps below.
All-electric vehicles (BEVs) emit the least amount of CO2 in 44 states. Hybrid vehicles (HEVs) are the most ecological choice in the remaining six states that are heavily dependent on coal as an electricity source: Indiana, Kentucky, Missouri, Utah, West Virgina and Wyoming. In year 2019, all-electric vehicles emitted the least amount of CO2 in 40 states.
PHEVs take second rank in 38 states. BEVs come in second for 5 of the 6 states for which they did not occupy first rank. HEVs occupy the second rank in the remaining 7 states.
HEVs are the dominant vehicle type occupying third rank, with 37 states. PHEVs come in third place in 12 states, and all-electric vehicles occupy the third rank in a single state: West Virginia.
The map displaying the fourth and last rank is boring to look at but nevertheless revealing. Conventional gasoline cars emit the most CO2 in all fifty states.
Methods of calculation
Readers interested to learn more can visit this USDE webpage, which provides technical and methodological details about electricity sources and annual vehicle CO2 emissions that were assumed in the calculations. The USDE online tool presents average values for sales-weighted model year vehicles. To better understand and interpret the mapped results presented above, it is important that you read the section on direct (tailpipe) and well-to-wheel emissions from the USDE web page, copied verbatim below.
Direct and Well-to-Wheel Emissions (copied from USDE)
Vehicle emissions can be divided into two broad categories: air pollutants, which contribute to smog, haze, and health problems; and greenhouse gases (GHGs), such as carbon dioxide and methane. Both categories of emissions can be evaluated on a direct basis and a well-to-wheel basis.
Conventional vehicles with an internal combustion engine (ICE) produce direct emissions through the tailpipe, as well as through evaporation from the vehicle’s fuel system and during the fueling process. Conversely, EVs produce zero direct emissions. PHEVs produce zero tailpipe emissions when they are in all-electric mode, but they can produce evaporative emissions. When using the ICE, PHEVs also produce tailpipe emissions. However, their direct emissions are typically lower than those of comparable conventional vehicles.
Well-to-wheel emissions include all emissions related to fuel production, processing, distribution, and use. In the case of gasoline, emissions are produced while extracting petroleum from the earth, refining it, distributing the fuel to stations, and burning it in vehicles. In the case of electricity, most electric power plants produce emissions, and there are additional emissions associated with the extraction, processing, and distribution of the primary energy sources they use for electricity production.