All-electric cars are zero-emission vehicles, but that's only a part of the story because a lot depends on the electricity source (while charging from the grid), which is not always zero-emissions.
Thanks to interesting charts, released recently by the U.S. DOE’s Office of Energy Efficiency & Renewable Energy for the U.S., we can take a look at the types of electricity sources in particular states.
There is no single zero-emission grid in the U.S. on a state level, but in some states, the share of renewable energy is already pretty significant.
Electricity sources by state
"When an electric vehicle is charged from the electrical grid, there are upstream emissions involved with creating the electricity. The amount of emissions is dependent on the sources used to create that electricity. Below is a map showing the approximate grid mix for each state, as well as the national average. To see estimates of well-to-wheel emissions for vehicles in a specific state, see the Department of Energy’s Alternative Fuels Data Center.
Source: U.S. Department of Energy, Alternative Fuels Data Center, “Electricity Sources and Emissions.” Data accessed on March 10, 2020."
Electricity sources and averages annual emissions per vehicle
Even when assuming national averages (there are multiple assumptions in the sources), electrification of vehicles offers a significant reduction in the CO2 emission per vehicle:
All-electric vehicles are the clear leaders, while the plug-in hybrids are only slightly ahead of hybrids.
Let's now take a look at California, which is the biggest car and EV market in the U.S. Thanks to the cleaner grid, the move to all-electric vehicles reduces emissions radically:
Of course, the ultimate goal is to have zero-emission electricity sources, including home solar, which hopefully will become more available and affordable over the years.
On the other side, in West Virginia, the grid that's heavily reliant on coal makes hybrids more effective in reducing CO2 emission (at least according to the study):
We would like to add also that we are aware that CO2 is not the only emission and that in this particular post we are just scratching the surface of the emission topic, as there is a huge amount of various factors involved in such comparisons to be fully objective.
You can see other states here.