CMU study finds limited dedicated residential parking and charging a significant barrier to mainstream EV adoption
12 November 2013
|Selected forecasts of US PEV sales with barriers to fleet penetration from limited residential charging infrastructure. Traut et al. Click to enlarge.|
An analysis by researchers at Carnegie Mellon University of parking and charging availability for electric vehicles in the US has concluded that limited availability of dedicated residential parking—and hence charging opportunities—is a significant barrier to mainstream electric vehicle adoption. The study, which was funded in part by grants from the National Science Foundation, CMU’s Steinbrenner Institute for Environmental Education and Research, General Motors, Ford and Toyota, is to appear in the journal Transportation Research (Part D).
The team, led by Professor Jeremy Michalek, assessed existing and potential charging infrastructure for plug-in vehicles in US households using data from the American Housing Survey and the Residential Energy Consumption Survey. The team found that while approximately 79% households have off-street parking for at least some of their vehicles, only an estimated 56% of vehicles have a dedicated off-street parking space—and only 47% at an owned residence. Only approximately 22% vehicles currently have access to a dedicated home parking space within reach of an outlet sufficient to recharge a small plug-in vehicle battery pack overnight.
Our estimates suggest that fleet penetration of PEVs beyond 22% will require residential infrastructure investment to increase access to outlets near home parking, and fleet penetration beyond 39% may require significant residential infrastructure investment because many households will need to upgrade their electrical infrastructure to charge multiple vehicles. Fleet penetration beyond 47% will require residential charging to be available for renters, and fleet penetration beyond 56% may require not only new chargers but also additional residential parking, with associated logistics, space implications, and environmental impacts.
All of these challenges to PEV penetration will be more severe in urban areas, where there are fewer charging and parking opportunities. Shared street parking and charging may be an option for PHEVs in residential areas, since it is not necessary to charge every night, but dedicated parking with guaranteed access to charging is necessary for BEVs and likely expected by customers who purchase PHEVs. Public charging infrastructure for street parking is likely only realistic for dense urban areas, although competing parking needs and charging needs will create logistical challenges. There are significant economic, logistical, and consumer convenience barriers to market penetration beyond households capable of charging at home.—Traut et al.
The study comes as vehicle manufacturers are introducing new EVs for sale and federal and state governments are offering incentives for purchasing EVs. States such as California also have introduced mandates that effectively force most automakers to sell EVs.
In their paper, the researchers note that the uncertainty from assumptions could be significant. For example, although the portion of vehicles with parking is 56% in their base case, it could range from 33% to 84% under pessimistic and optimistic assumptions, respectively. The parameter with the greatest influence on the optimistic case is the prevalence of driveways at households that also have garages.
If many households have driveway space that could be used for dedicated charging without blocking garage access, the potential for residential charging may be higher than the base case estimate. The parameter with the greatest influence on the pessimistic case is the portion of parking spaces that are unavailable for parking vehicles.
The researchers recommend that PEV penetration forecasts and other studies that pose PEV penetration scenarios consider the effect of limited residential parking availability on the potential for PEV market penetration.
On the whole, less than half of US vehicles have dedicated off-street parking at an owned residence in a location suitable for installing a charger. That means if we want more than half of the vehicles on the road to be electric, we’re going to need major changes in residential parking—and that doesn’t happen quickly.—Jeremy Michalek
Elizabeth J. Traut, TsuWei Charlie Cherng, Chris Hendrickson, Jeremy J. Michalek (2013) “US residential charging potential for electric vehicles,” Transportation Research Part D: Transport and Environment, Volume 25, Pages 139-145 doi: 10.1016/j.trd.2013.10.001
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