DoE Releases Report On Electric Vehicle Charging

JAN 6 2015 BY MARK KANE 38

Residential Energy Use by Time-of-Day and the Duration of Charging Sessions. (Note: Time is active charging time only.)

Residential Energy Use by Time-of-Day and the Duration of Charging Sessions. (Note: Time is active charging time only.)

Percentage of Charging Sessions by Time-of-Day for Commercial Charging Stations at Progress Energy

Percentage of Charging Sessions by Time-of-Day for Commercial Charging Stations at Progress Energy

The US Department of Energy (DOE) published a new report on electric car charging presenting customer behaviors and impact on the grid.

Data comes from different projects made by six utilities:

  • Burbank Water and Power (BWP)
  • Duke Energy (Duke)
  • Indianapolis Power & Light Company (IPL)
  • Madison Gas and Electric (MGE)
  • Progress Energy (now part of Duke Energy as a result of a merger in 2012)
  • Sacramento Municipal Utility District (SMUD)

In total, over 270 public and over 700 residential charging stations were evaluated.

According to the report, the electric power industry expects a 400% growth in annual sales of plug-in electric vehicles by 2023, so not strange that utilities are interested to learn something onhow to take advantage of electric cars and not end up with a black out.

For now, the impact of electric car charging on the electric grid is negligible due to the low number of plug-in vehicles, however typical load curves already can be determined, as well as finding that only a few percent of charging sessions are longer than 4 hours (and 12 kWh). It should be easy then to encourage EV owners to charge off-peak during the night.

Major Findings

“There are relatively few plug-in electric vehicles on the road today; as a result the six SGIG projects focused on establishing the charging infrastructure with a relatively low number of stations and evaluated a small number of participating vehicles. As expected, project results showed negligible grid impacts from small-scale electric vehicle charging today, but gave utilities important insights into the demand growth and peak-period charging habits they can anticipate if electric vehicle adoption rises as expected over the next decade. Utilities face a challenge in determining when their customers purchase electric vehicles, and where and when they will plug-in to satisfy charging needs.”

“Given the current rate of customer electric vehicle adoption, utilities are considering plans for electric vehicle charging programs. For example, BWP analysis showed that with a 25% per year growth in usage at public charging stations, utility investments could have a seven-year payback, which would be a financially attractive business case for some utilities. Table 1 provides a summary of the key project experiences from the six projects.”

Table 1. Summary of Key Project Experiences

Table 1. Summary of Key Project Experiences

Full report can be found here: “Evaluating Electric Vehicle Charging Impacts and Customer Charging Behaviors: Experiences from Six Smart Grid Investment Grant Projects”

Categories: Charging

Tags: , , ,

Leave a Reply

38 Comments on "DoE Releases Report On Electric Vehicle Charging"

newest oldest most voted

Thanks Mark! This comes in perfect timing, as I am preparing a letter-to-editor on that U-Minn study reviving that ‘Coal Cars’ myth.

Hi Assaf, Since The FLAWED University Of Minnesota study of Alternative Fuel Efficiency hit the Cyber Echo Chamber two weeks ago, I have been hammering back out this statement entered into the Congressional Record By US Senator Lamar Alexander (R-Tenn) in the spring of 2011. The good Senator States This: “A conservative estimate is that we have an amount of electricity unused at night that’s equal to the output of 65 to 70 nuclear power plants between 6 p.m. and 6 a.m.,” Senator Lamar Alexander (R-Tenn) stated before the Senate Energy and National Resources Committee. “I suspect that’s probably our greatest unused resource in the United States. If we were to use that to plug in cars and trucks at night, we could electrify 43 percent of our cars and trucks without building one new power plant.” Ed. Any ‘Study’ that does not incorporate this massive unused, FREE, Over Generation of waste electricity, off peak, available every day, is flawed, in my opinion! Links Go To Torque News And Forbes Both Reporting This- Meanwhile, the Department of Energy has released its most recent ‘Workplace Charging Challenge entitled, “Progress Update, 2014 – Employers Take Charge” Link Goes To DoE… Read more »

The observation that most public charging occurs during peak time suggests that costs will always be skewed against public charging, because demand has a big impact on electrical infrastructure costs.

The basic concept of daily driving using energy stored from overnight charging will inevitably end up being the dominant mode. Public charging will only be used for unusual corner cases, like longer distance trips.

Good point, however you pre-assume drivers will have access to overnight charging.

Some drivers might never have that, and for them public charging will be a lifeline.

Another important use case are commercial and public fleets. While they can usually start the workday at 100%, they might deplete and need midday recharging.

For these and others, we must remember that in most workdays the peak is actually in the evening, with a secondary morning peak. So while not as ideal as overnight, a substantial amount of midday charging can still be tolerated.

In addition, midday charging is useful for absorbing solar energy during its peak production hours, without needing to build storage systems.

In short, don’t hasten to throw out public L1/L2 charging 🙂

Yes I did make that assumption, but I think it is reasonable now that more municipalities are mandating charging enabled capabilities in all new buildings, including rentals.

Public only charging is not impossible, but for now EVs will remain a much harder sell for most people who do not have any overnight charging capabilities.

As for commercial vehicles, I think they will either be sized to support a full day’s work (eg local delivery vans) or use dedicated special purpose facilities (eg electric buses at terminals). Similar approach as today’s NGV or propane fleets.

Regardless, I’m right there with you on wanting more public charging facilities, especially if someone else pays for them!

Most drivers WILL have access to night charging. It is only the rare hardcore EVer that would buy an EV without access to night time charging. That is horribly inconvenient.

Apartments with the ability to charge at 110V exist. When I was between houses, I had to rent a condo with a garage for a few months. No problems with charging in the garage in the rental.

Right now the small number of renters who buy plug-in vehicles can get by on being very selective on where they rent, and selecting properties where they can charge. Maybe even be bold enough to get a landlord to approve adding a 240V charging station if they have a good relationship and the right setup. I just don’t see plug-in vehicle owners who rent being a huge problem in the near term. The solution is always to just rent somewhere else at this point.

We are a long ways from being at the point where renters just can’t find anymore properties left anywhere that they can charge. I think it will be a long time before that much market saturation causes that problem

I’m going to agree with Assaf here, but for different reasons. After home charging, workplace charging is and will continue to dominate. I know more than a few people who use workplace charging rather than home charging, especially if it is an employer benifit.

And that is ALL midday charging.

For my first year of EV driving I was not able to charge at my apartment. I relied on public infrastructure and an arrangement I made with a Nissan dealer near where I lived (and I drive a Fiat). I traded regular donut deliveries for the staff for electricity. I would have to leave my car overnight 3-4 nights a week in order to charge (I could make 2 trips to my workplace and then be close to dead). This meant I had no access to a car on the nights it was charging because they used vehicles to block the driveway for security. My husband actually walked to the emergency room the one night this past year he needed medical attention (about half a mile). I finally convinced my apartment manager to reserve the parking spot next to my back gate so I could park there and charge overnight – the cable that came with the car could reach the outlet by my sliding glass door. If I was not in this particular apartment or a very few others on this property it would not have been an option. For the longest time they said the cable would be… Read more »

I suppose somebody needs to write this kind of report that states what EV and PHEV owners already know.

The only non-obvious point in Table 1 is the inter-operability problems noted by SMUD. However, this is related to demand response which must have been a pilot project. The point of the pilot projects is working out these interop issues.

Its useful to have a current data point to reference when folks trot out the “EVs will break the grid” talking point.

“….requires a licensed electrician and occasionally service upgrades”

This is untrue.

Any homeowner can install their own charger, given that they permit it with the local building dept and have basic wiring skills.

Kosh — I agree, as written it is untrue, because a licensed electrician is not always “required”. It all comes down to local building codes, so there is never one single answer. In some cities, building code does indeed require a licensed electrician for anything that requires access to the inside of the panel, including adding any new circuits (120V or 240V). Depending upon jurisdiction, a permit and an inspection may or may not be needed to install a 240V circuit. In most jurisdictions, homeowners can indeed install their own new 240V circuits. In my jurisdiction, the rules are pretty clear. Our licensing dept says outright: “As a homeowner you are permitted to perform electrical work on your primary residence without an electrical license.” Then they make you swear to this: “I affirm that, as the homeowner, I will do all of my own electrical work. I understand the correct way to do electrical work and when to request inspections.” Homeowners certainly can educate themselves on proper code, inspection, and wiring, and install their own plugs. I’ve personally installed two of my own 240V/50A drops in two different houses I’ve owned. I don’t necessarily suggest that other homeowners all do… Read more »

Yes.. not Required. But in the vast majority of cases it will be done by an installer.

I would have done it myself but I required a ‘service upgrade’ since my main panel was a bit small.

Here in IL if you use an IL Commerce Commission licensed electrician, you qualify for a 50% rebate on hardware and installation costs.

That took my 40A line install and 7.7kW charger costs down to ~$700.

Well worth the tradeoff!

Too bad DOE thinks EVSE installs “require a licensed electrician”, when all that’s needed is the outlet. Plug ready 240v EVSEs are available, without having to bring an electrician in. I think JuiceBox is near its UL listing.

I wonder what DOE thinks “average load” is, if 19kw is higher? There is a big jump between dwellings, and detatched homes which are built with no less than about 40kw (~200 amp service) these days.

Good points.

With plug-in L2 EVSE’s like those offered cheaply enough by Clipper Creek, all that is needed is 240V, 30A circuit or essentially a dryer outlet. How hard is it to do that?

The 19kW load is only specific to a Tesla HPWC feeding a Model S with Twin Chargers. It certainly does not exceed the load for most large, single family homes. It may exceed the typical draw, but not the capacity. Most large, single family homes have 200A service and the HPWC draws up to 100A.

All in all, not sure if the report has any useful conclusions. Under utilized public charging stations? Well, take a look and see what the rates are. Typical rates are $0.50/kWh (plus other charges) which is ridiculous.

The DOE report lacks data and insight on energy use (kWh used per day), and instead focuses on peak power (kW). A histogram of daily energy use would provide much more useful information allowing charging power to be adjusted to actual need. eg: A Tesla has the capability of charging up to 20 kW, but was this power level maintained for 25 min, or 7 hours. The charging level on Tesla’s is adjustable and can be throttled. A bit of education, or automation could reduce peak power. Based on an average driving distance of ~35 miles per day, approx. 10 kWh is required per day. A smaller battery means charging every day, while a larger battery allows going many days between charging sessions. The DOE study states that “the average demand was 3-6 kW”. Not noted is over 80% of BEVs have 6 kW or greater charging capability vs. PHEVs where 3 kW charging is more the norm. The report also lacks data on amount of power homes are wired to handle, the daily time use of power in typical home and average daily energy use. While charging an PEV can be a larger load the lack of context overlooks… Read more »

“10kwh is required per day”

This isn’t a good assumption, since that can nearly double to 18 kwh when it’s cold outside with the same basic assumption that you’re driving 35 miles a day.

At least, that’s what people on the Canadian Nissan Leaf facebook page are saying. As usual, your mileage may vary.

“The 19kW load is only specific to a Tesla HPWC feeding a Model S with Twin Chargers. It certainly does not exceed the load for most large, single family homes. It may exceed the typical draw, but not the capacity. Most large, single family homes have 200A service and the HPWC draws up to 100A.”

hmmm. Yes and NO.

19KW is NOT more than the PEAK capabity of most large single family homes (you will be surprised of how many CA homes built before 1990 only have 100A service). But most homes don’t sustain 19KW for 3-4 hours. That is the big catch. Home loading are highly variable so the Utility company only allocate enough power for homes to sustain % of the max peak draw. So, if there are 3 to 4 Tesla on the same street a local transformers will be needing upgrade soon.

This is why the study says “Utilities face a challenge in determining when their customers purchase electric vehicles, and where and when they will plug-in to satisfy charging needs.”

You should always notify your utility that you have added EV charging equipment (especially if it is over 30A) so that they can plan the neighborhood distribution appropriately. If you sign up for an EV rate plan, you’ve already done it. When I changed my plan, PG&E simply asked me what kind of EV I purchased, not what kind of equipment, because they already figured out that the vehicle is what determines the maximum load.

Could the 19kW be a Tesla HPWC with a Model S with dual chargers?

It couldn’t be anyone else.

They do say load, not capacity. A 19 kW continuous load is a big one for a residential service.

There are two kinds of people in the world, those who can do things and those who cannot. The latter is a much, much larger group, and includes all the people in my neighborhood who call an electrician to change the batteries in their smoke detectors. Hard to believe, but truer than you would think.

Personally I find it unfathomable that people actually call “Geek Squad” just to install a TV, but that’s the way it is in the modern age.

The only way to eliminate the electrician for the incapable masses is when new houses come with a 240V outlet (like a dryer or range outlet) as standard equipment in the garage. Then L2 chargers would be plug’n’play (although I’d wager many will still call an “installer”).

A complication for homeowners is that there are numerous 240V outlets/plugs that cause confusion. For example, my EVSE came with a NEMA 6-30 plug while most dryer outlets are NEMA & L14-20, NEMA & L14-30, etc.

Yes, that’s a problem.

It would be very helpful if the next NEC revision defined one outlet type that must be provided for all EVSE enabled garages.

I disagree. There is a reason why there are already multiple “standards” for different plugs. If you force just one standard, more people lose than win. Either:

1) People will either waste money installing thicker wiring and more expensive plugs than they would ever need for way too large a power source.


2) People will end up with a plug that has too low a power rating, and suffer with lower charging rates compared with what their vehicle can handle.

Very few people would end up being “just right” with one mandated standard plug size. If there was already one “just right” size, car companies would have already standardized on it. One “just right” size doesn’t exist, so it takes a bit more effort sometimes on the initial install to get exactly what is needed. I don’t see that changing any time in the near future.

The study notes that public charging station use overlaps with peak grid demand, but fails to mention that all the solar panels that EV owners have installed also overlaps with when public charging stations are being used.

The net impact to the grid of all EV owners, with all of the collective solar power they have installed, is actually to REDUCE peak grid demand.

The way trends are going, EV ownership has been tightly linked to solar panel installation. As long as this trend continues, EV owners (with their solar panels) will collectively continue to be a net benefit to the grid at peak demand times in most of the US. Any exceptions are the exceptions that prove the rule.

Was going to say exactly the same thing.

IIRC other studies have said up to 30% of EV owners also have solar PV.

The charts showing public charging demand very closely mirrors daylight hours (just go look at the CAISO Today’s Outlook page and Renewables Watch page), so solar is a natural fit for generating electricity and will directly offset public charging demand.

Currently the typical EV driver only gets about 10% of their energy from public charging, so with up to 30% of EV owners having solar PV, they are already more than offsetting any daytime demand from public charging.

Still, this only makes the case to install solar PV with charging stations.

While that may very well be true today because both solar and EV users tend to be the same technically savvy first adopters, it would not be a good idea to establish that link, especially when many urban EV users might not have any access to solar capabilities because they live in townhouses, condos, apartments, etc.

QCO — Just because you live in an apartment or highrise doesn’t mean you can’t participate in solar or other green energy. They just have to do it a bit differently than folks who have lots of roof space on their single-family home.

The first solution is called a “Solar co-op”, where people get together to own shares in a private solar farm built elsewhere.

Another solution is programs like “Wind Source” from Xcel Energy, where your electricity payments go to expanding wind energy production, offsetting your grid consumption.

One cool thing about green energy is that it doesn’t actually have to be on top of your own house for folks to participate.

Yes, all that is possible. But those options are independent of EV ownership and should be promoted on their own merits, regardless of whether one even owns a car. Similarly, owning an EV should be promoted on its own merits, regardless of where one buys power. That was the point.

I’ve been intensively studying energy and climate issues for a decade, and if there’s one thing I’ve learned it’s that we have to be very careful about relying too much on the sweeping generalizations we read online or even in things like DOE reports. I’ve had arguments with people about how much CO2/mile my Leaf emits because they assumed that my electricity supply has the same composition as my entire state (NY). In fact, I pay a tiny bit more for 100% green electrons, from wind and small hydro sources, and my marginal CO2 emissions are essentially zero. But, as I so often point out, we’re still very early in this whole electrification of transportation adventure, and, as we economists like to say, the market is still sorting itself out. There will be false starts, surprises, both positive and negative, and a whole lot of squishy social science mixed in with the technology, e.g. some old school car guys who detest electric cars and will resist embracing them until forced. Plus we’ll have to endure some howling idiocies from companies like Honda and especially Toyota who will keep pushing HFCVs and trashing EVs even while the rest of the industry… Read more »

“only a few percent of charging sessions are longer than 4 hours”

I suppose then that this study was limited to people with 240V chargers. That will skew the results.

If you’re using 120V charging, your load is insignificant, almost by definition.

That weekday charging graph is probably spooking some utilities. It looks like everyone is plugging in their EVs as soon as the get home. This is REALLY bad for utilities as this is helping add to the ‘second peak’ of the day when people come home and turn on their TVs & electric ranges.

This is especially bad in places like California with a lot of solar because this surge in demand comes right as all the solar PV electricity is stopping.

They need to do more time-of-use metering to force people into programming their cars not to start charging until midnight.

I’m guilty of charging up when I come home but that is mainly because my EV has no programming system for charging . . . nor does my EVSE. :-/

Then you can just take a very litle walk and plug it in before going to bed.
If you’re day living of course:-)
What kind of car has no timer anyway?
Easy for me to say because peak ain’t such an issue here in Québec. Except in very cold climate that will comme in soon.
98% hydro is something that help.
Even then when the utility call for reducing demand I’ll just differ the charging.
Still have a long way to go to make a blackout here.