Mind the gap: Testing the EV charging network
Carnegie Mellon researchers develop a metric to measure the gaps in EV charging coverage across the country. Findings show the significant work that lies ahead in deploying charging infrastructure, especially among rural areas.
Although electric vehicles (EVs) present a considerable opportunity to lower our greenhouse gas emissions, EVs currently only account for 1% of vehicles on the road in the U.S. One reason consumers have reported hesitation in purchasing EVs is “charging anxiety,” or concerns about losing power without access to a nearby, quick, and reliable charging station.
To instill confidence in buyers and encourage EV adoption, the federal Bipartisan Infrastructure Law and National Electric Vehicle Infrastructure (NEVI) program are helping to deploy fast chargers along select main highway routes called alternative fuel corridors, or AFCs. Despite this investment, large gaps stretch between charging stations in many parts of the country, disproportionately affecting rural counties and inhibiting long distance travel.
Seeking to better understand the current and future state of EV charging coverage in the U.S., researchers from Carnegie Mellon University’s Department of Civil and Environmental Engineering are assessing consecutive charging coverage on all National Highway System roads. In research published in Nature Communications, the team evaluates individual states and counties by the percentage of roads, weighted by traffic, that are without 50 mile or more long gaps between charging stations within 500 miles of any given county.
We found that many states have a long way to go before we achieve the consecutive charging coverage that can ease the minds of consumers.
Corey Harper, Assistant Professor, Civil and Environmental Engineering
“There is a chicken and egg problem with EVs and charging infrastructure. Charging stations need EVs to be profitable, but consumers hesitate to purchase EVs due to a perceived lack of chargers,” said Corey Harper, assistant professor of civil and environmental engineering. “Using our metric, we found that many states have a long way to go before we achieve the consecutive coverage that would ease the minds of potential buyers.”
The team discovered that states such as California, Nevada, and those in New England generally have adequate charging coverage when looking at stations with slower charging speeds and fewer chargers per station. But, when implementing NEVI-compliance standards, which mandate at least four fast chargers per station, the effective coverage area shrinks. Consequently, while drivers in these states can find a charger every 50 miles, they may face wait times and queues due to lower power ratings and fewer chargers available at each station.
Even with NEVI’s plan to install fast charging stations along AFCs, while the northeast, California, Nevada, and Arizona would achieve continuous charging coverage, more rural states such as North and South Dakota, Arkansas, and Texas could not provide the same level of assurance for EV drivers. NEVI would need to deploy charging stations on 1,900 road segments to meet the plan’s goals, and this number rises to 4,500 segments to extend fast consecutive charging coverage to all highways, including those rural states.
To expedite this process, EV manufacturer Tesla has made recent arrangements to open some of their Supercharger network and share their connector design with select car manufacturers. However, the full potential of this collaboration remains untapped. Making the Tesla charging network universally accessible could have a huge impact on the cost and labor in realizing NEVI’s vision.
“By adding magic docks to Tesla Superchargers or open-sourcing their connector design, we could achieve fast consecutive charging coverage with 500 fewer new stations,” said Harper. “We estimate that this could save between $166 and $332 million in NEVI programming costs.”
The team believes their findings can help policymakers and consumers navigate the realities of EV charging access. Looking forward, they hope to extend their research to medium and heavy-duty electric trucks, for which charging access lags significantly behind that of everyday cars.
Often we talk about the distance capabilities of gas compared to electric cars. Now, we have a forward-looking method for estimating the range limitations.
Destenie Nock, Assistant Professor, Civil and Environmental Engineering
“Ultimately, we hope to inform policy development at both the federal and state levels and show that, while most of the country will have sufficient coverage once AFCs reach NEVI-compliant status, additional work needs to be done to ensure charging access in rural areas,” Harper explained.
“One of the largest values of this study is understanding the true range limitations for the national build out of EV infrastructure,” said Destenie Nock, assistant professor of civil and environmental engineering. “Often we talk about the distance capabilities of gas compared to electric cars. Now, we have a forward-looking method for estimating the range limitations."
The CMU team, led by Ph.D. alum Lily Hanig (EPP’24), conducted this research in partnership with the
U.S. Department of Energy’s National Renewable Energy Laboratory and Lawrence Berkeley National
Laboratory.