Chevrolet Spark EV at CCS fast charging station in San Diego.
For anyone who follows the U.S. electric-car market even casually, some new data on which states have the largest numbers of them probably doesn't count as news.
A recent survey shows that California leads the nation in plug-in electric car registrations--with almost half of the nation's plug-in cars plying its roads.
That statistic comes from the U.S. Energy Information Administration (EIA), which analyzed the state of electric-car adoption in the U.S.
According to the EIA, there were 70,000 battery-electric cars and 104,000 plug-in hybrids on U.S. roads at the end of 2013--put of roughly 226 million registered vehicles.
U.S. electric-car registrations per 1,000 cars. Graphic by U.S. Energy Information Administration.
For 2014 thus far, they make up 0.7 percent of the roughly 226 million internal-combustion cars and light trucks in the U.S. car sales.
But the percentage of plug-ins has at least steadily increased over the past couple of years--from 0.6 percent in 2013, and just 0.4 percent in 2012.
Even in California, plug-in cars still represent about 5 out of every 1,000 registered vehicles.
The Golden State is one of just three states with more than 3 plug-ins per 1,000 registered vehicles, along with Washington and Hawaii.
California passed the 100,000-plug-in-car mark back in September, and hopes to have 1.5 million of these vehicles on its roads by 2025.
Cleaner vehicles have been a priority for the state's policymakers since clouds of smog first appeared over its major cities many decades ago.
Like many states, California offers incentives to encourage the purchase of new zero-emission vehicles.
Residents can get a $2,500 rebate for a battery-electric car or $1,500 for a plug-in hybrid, and their drivers can also gain solo access to carpool lanes.
2015 Kia Soul EV and 2014 Nissan Leaf, at Blink DC fast charger - Fife, WA
Thanks to a zero-emission vehicle mandate, there are also several electric-car models sold only in California. These "compliance cars" are sold solely to meet that requirement, and only in the numbers required to keep their makers legal.
Most states are far behind California so far, but at least a few could catch up soon in proportion (if not in total number).
Nine other states--Connecticut, Maine, Maryland, Massachusetts, New Jersey, New York, Oregon, Rhode Island, and Vermont--have agreed to adopt California's electric-car standard.
Including California, these states represent about one quarter of the U.S. light-duty vehicle market. They have all adopted rules stating that, by 2025, at least 15 percent of vehicles sold within their jurisdictions must produce no emissions at all.
[EDITOR'S NOTE: An earlier version of this article incorrectly said that electric cars represent 0.7 percent of total vehicle registrations. They in fact represent 0.7 percent of new-car sales so far in 2014. We have corrected that statement.]