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CMU study finds limited dedicated residential parking and charging a significant barrier to mainstream EV adoption

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



Hence my support for inductive charging, which would make it a lot easier to charge vehicles without garaging, especially in urban areas.

It also contributes to my support for fuel cell vehicles, which can likewise reduce the need to put chargers in every awkward location.


@Davemart - I don't see how inductive charging makes it easier to charge without garaging - all you need it a long enough lead and you can park the car anywhere within the radius. Inductive charging requires you to park in the right spot every time.

A few other comments:
22% EV penetration would be a huge step, and we are a long way off that.
If you have 2 or more cars in a household, you probably want one EV and one ICE to start with. You don't really need 2 EVs - you are better off with an ICE in the mix for long runs.

A problem occurs with shared parking - you have to reserve some spots for EV charging, and this reduces the amount for everyone else - whether or not the EV people turn up and use their spots.



You must have excellent public liability insurance and an understanding insurance company if you intend to run power lines across sidewalks.

The problem is most acute in all the urban areas to which EVs are most suited, particularly in European and Asian cities where there is simply no room to have charging posts on the sidewalk.

Just google in street view the streets of Bristol, England, where I live, for instance.


If charging per mile costs are significantly cheaper than gas - 50% or less, I think that you'll find some interesting market- and community changes...
- electro-looting - plugging into a neighbour's or unauthorized work/public receptacle.
- electro-marketing - letting neighbours/customers plug into your outlet for a price - often creating mini-markets in a neighbourhood
- electro-parking - parking lots expressly made for EVs with special privileges
- electro-benefits - maybe no dental or defined pension at your work but hey, full charge-ups on workdays/ new/used house sale or desperate landlord installs dedicated chargers as upgrade/feature
- electro-VIP - malls, parks, public buildings use charger stalls as preferential close-up or sheltered parking as a service/ token 'green upgrade'
- electro-regulation - HOV lanes nothing - you want PEV uptake? dedicated lanes, parking spots, charging areas, portion of all new buildings, anything lifestyle upgrade will push it...
- electro-swarming - suddenly in 2030 we start to see a trend that number of cars on roads increase, total miles increase, miles per car increases, cars per family increase, electified-exurbias increase, worst congestion ever/ transit use decreases... pro-car urban design, pro-car inter-state upgrades, - if batteries give us 300miles and/or 600miles total on an extender for <$35k... careful what you wish for... (not that I have anything against a 70s/80s level of car use again)


Park the car in your slip and charge it there.
(Assuming you have one).
If you park outside on the street (as you infer), you need the council to build (or allow you to build) a charge point.
The government could bring in rules forcing them to allow this (piloting it for a year or two to see what happens).

For that you need a dedicated parking spot, but less accurately placed than an inductive charger.

Inductive charging may have a place in high end luxury cars, but there are significant downsides. In a parking lot scenario, you have to have an inductive pad for every spot an EV will park. A conventional charge station with a decent length cord can be positioned in the middle of four parking spaces (ideally, two facing two) and any one of the four spaces could be serviced. Not only does that alleviate ICEing, but also the common case where a one EV has finished charging and another is waiting.

Inductive charging is inefficient with the use of space as well as energy. If you're in your own garage, and want to pay for that inefficiency, I'm ok with it. But as a public infrastructure, it would be a much more expensive build-out. There are aesthetic and convenience advantages to be sure. But at what cost?


Please stop the subsidies and law requirement toward bevs and start the rollout of hydrogen fuelcell car. This study is clear , we cannot charge bev easilly for the majority it is impossible to recharge and if we factor in vacation and weekends errants then it's even worst and no consumers are interrested in bev cars.

Start hydrogen commercialisation now, this is an order..

You must have excellent public liability insurance and an understanding insurance company if you intend to run power lines across sidewalks.

I think you'll find that overhead arms for wires are just as feasible as overhead arms for street lighting.

- electro-looting - plugging into a neighbour's or unauthorized work/public receptacle.

ChargePoint deals with this by having the charger shut off when disconnected from the vehicle.  An RFID card is required to activate the charger again.

- electro-parking - parking lots expressly made for EVs with special privileges

Many parking lots already have piers or islands with foundations for light poles; wires already run to them.  If the wires are in conduit with room for more conductors or have extra capacity, charging can be provided next to those islands.  With the lights off during daylight, the full capacity of the existing circuits can be used for charging.

This could be rolled out today.  I'm all for anything that can get this stuff to the public ASAP.

Notice that a.b. always wants the thing that's not ready for prime time instead of the solution that's here today.  He's a shill for the fossil-fuel vendors.


It seems that up to 50% of inner city dwellers may have problems charging their PHEVs and BEVs overnight.

For them, FCEVs may fit their requirement better?

For a long time, posters have claimed that PHEVs and BEVs are the best option because infrastructures exist for everybody but that may not be the case for many car owners.

The co-existence of both EV and FC technologies may be the best option?

If ONE fit all technology is selected, FCEVs would have to be the one?


@EP said:
'Notice that a.b. always wants the thing that's not ready for prime time instead of the solution that's here today. He's a shill for the fossil-fuel vendors.'

Way too harsh, EP.
Gorr is a poster who is always polite, if a tad eccentric.
If you make an accusation, be prepared to produce the evidence to back it up, or be a gentleman and withdraw.
There is zero evidence that ab aka gorr is paid to make his rather unusual observations, so please withdraw, as you are way below your usual standards here, EP.


Building a system of overhead gantries is a very different proposition to what mahonj proposed, of simply plugging in your car and from a wire run across the pavement.

Whatever may be the case in the US, there is zero chance of overhead gantries being approved in Europe, where electricity supplies are certainly not allowed to do this.


I have solar on the roof and a Volt in the garage. 110 feeds that car nicely. Our son, condo has lots of outside covered parking, as well as one car garages. The standard plug is all one needs for overnight recharging. However, if his (and other) HOAs put solar on their outside shelters, which already have lights and plugs, PHEVS/EVs could charge outside, without dragging cords over pedestrian areas. Also the HOA could take energy credits to lower outdoor lighting, swimming pool and common area energy, using those savings to provide better services or reduce HOA dues.


Perhaps you would produce the referenced figures to substantiate your claims.

Is it cheaper to build a central point capable of charging 4 cars simultaneously, or to put 4 plates in the road in series?
I am talking of course about prices in series production, not the hand built early prototypes.
If so, by how much, and on what basis are the figure calculated?

More efficient?
The sources I have indicate that wired and wireless run pretty close.

Here are the figures for the Leaf, which average around a 20% loss wall to wheel:

If you happen to read French, losses on the Zoe are similar:

Whilst for inductive/resonant charging here is Qualcom:
'The efficiency of Qualcomm Halo WEVC technology is comparable to conductive charging systems at similar power ratings. The industry target is for a commercial WEVC system to be 90% efficient and above. A very high quality conductive charging system could have efficiency figures in the mid-nineties due to losses in isolating and control circuitry, components, connectors and cabling. However, some conductive charging systems are reported to have losses around 15% or more. It is accurate to say that conductive charging will usually be 1 or 2% more efficient than wireless. As power increases say from 3.3kW to 6.6kW and up to 20kW the charging efficiency can increase since the standing losses are the same for all power levels. For example, the 7kW system on the Rolls Royce Phantom 102EX Experimental Electric Vehicle was shown to operate at over 90%.'

I could support that with many other links from other sources all indicating that losses from non-wired charging are not very significant.

So, please produce your sources, or withdraw.


Cordless charging makes sense in many places, work place parking lots being among those. You park your car for 8 hours while working, why not charge it during that time period?


Why not piggyback on the existing wiring for the light poles in the parking lot, and install existing corded chargers?  It's a great deal cheaper.  About the worst that could happen is the chargers would have to be programmed to back off the current delivery to respect the limits for the wiring.


You have accused ab of being a shill.
Produce your evidence, or retract.

Pretty low, EP.


I was not proposing to run a cable across the pavement - as @Dave says, this would be crazy.

I was suggesting that you put a charge point near the kerb, run the wire under the pavement (from your house, or wherever) and have the fixture near the road, rather than the house. This is done for parking meters and lots of fixtures so it shouldn't be a technical problem.

It would become a problem of will - between the EV owner and the council (who might object to extra road furniture) hence government mandating it.


Hi mahonj.

I misunderstood you, as when the subject has cropped up some people in all seriousness have proposed that people could get out their extension cords.

As I linked here for another poster who proposed fixtures near the road, without receiving any response presumably because they did not have an answer, in many place in the world it is extremely difficult to impossible to put in more street furniture, and that includes many of the cities to which EVs are most suited.

Google up Wick Road, in Bristol, for instance, near where I live, go to 'Street View' and try to imagine getting more street furniture in.
Add to that that there is zero chance of overhead wiring getting a permit. That does not happen for anything else, including electricity, and it is not going to happen for charging electric cars.


Cordless charging is more convenient. They made the EV1 inductive for safety in the rain. Corded chargers by the curb are targets for vandals.

Let's go where we want to go anyway, to cordless inductive charging standards, where ever you park you charge with NO hassles. This makes it all the more attractive to the buyer and user.

Roger Pham

Even for an urban area wherein cars are parked curbside right next to pedestrian walkway, a groove deep enough to accept the extension cord from inside the house can be made across the walkway. Then the cord is laid on the deep groove and sealant applied to glue it into the groove and protect it. Then, a charging socket can be made flushed with the curb right next to the car. Then, the charging cord from the car can plug in to the socket flushed with the curb.

REsult: No visual impact and very low-cost installation within a few hours by one person. Remote-controlled switch similar to a garage door opener built-in to the PEV can be used to turn the current on or off to the curb-side charging socket in order to avoid "electro-looting" and vandalism. In public road, cell-phone can be made to activate the curbside charging switch for billing purpose.

Very simple and easy way for curbside charging of PEV. In areas with frequent rain, the curbside charging socket may have a protective cover that can be opened and closed via remote switch inside the EV to avoid moisture and vandalism! With money to be made from automated-billing public curbside charging, the infrastructures will be developed privately and will happen effortlessly!

Bob Wallace

In garages, public and private, cables can be laid on the concrete surface and protected by glue down "conduit" for retrofits. These charging "turtles" are already being installed. With new construction conduit can be laid during the pour.

For street side and open air parking lots it's fairly simple to cut a slit trench in blacktop for the conduit/wire run. Just set aside a 'No Parking' day and run right down the street.

What needs to be developed is a removable wireless charging unit which can be taken up during resurfacing and replaced once the road roller has finished. And it needs to sit flush with the surface so that it won't be scraped off by snow plows.

Plugged charging is more efficient, but only by a small amount. Most people are going to opt for wireless charging if it costs them only pennies per day.

All the important stuff will be below pavement where it will be more difficult to mess with. Just do wifi charge limit setting and billing.


I knew there was someone who was seriously advocating running extension leads out!
Whatever may be the case in the US, in Europe there is absolutely zero chance of this being authorised.
For the US I await with interest the result of thee first court case where someone manages to allege harm from the installation.

To say this is a wholly impractical notion which cannot possibly exist in anything remotely like present legal and regulatory environments is to understate the case.

EP: You have accused ab of being a shill. Produce your evidence, or retract.

Just look at what he says, Dave.  He's always "ready to buy"* things that (a) aren't on the market, and (b) would maintain the competitive position of the existing oil majors, like full fuel compatibility.  Any and all such efforts are diversions from things which disadvantage the oil majors.  He's never for anything like PHEVs already on the market or CNG cars that could be rolled out immediately.  And take this:

Start hydrogen commercialisation now, this is an order..

A technology requiring the filling-station model, which advantages NG and even gasified coal over non-fossil energy sources... absolutely on-message for a fossil-fuel shill.  He may not be paid, but if it walks like a duck...

* I see that phrase in a great many a.b comments, and I don't recall anyone else using it.  It's like an intellectual DNA test.


A shill is not someone who has a different opinion to you, but:

'A shill, also called a plant or a stooge, is a person who publicly helps a person or organization without disclosing that they have a close relationship with the person or organization.'

Since you have zero evidence of any such relationship, then you are making entirely unwarranted personal accusations.

Gorr in my view is in any case a rather eccentric individual, who informs us that he hopes to be in a position to buy a new car in, I believe he said, 2022 or thereabouts and his assessments of the technologies on offer are with a view to buy at that point, and not before.

I somehow doubt that Esso has employed someone like him to support their schemes, however nefarious those schemes are held to be.

Since he is also a perfectly polite and well mannered individual, who never indulges in personal criticism of an other poster, I would suggest that you owe him a personal apology.

It would also help if you stopped not only making unwarranted accusations with not a shred of evidence, but stopped indulging yourself in perfectly barmy conspiracy theories.

Really, EP.


Another (future) way to charge EVs without a power cord may be to micro-wave the energy from one

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