Pecan Street Project: EV Charging Not Likely to Stress Grid

OCT 26 2013 BY SURDASM 16

We’ve all heard this claim before: “If EVs ever go mainstream, say bye-bye to the power grid when everyone plugs in after work!!!!”

One of the first studies to test this hypothesis concludes that … well, no, that’s not very likely to happen.

The Pecan Street Research Institute conducted a trial over the summer in Austin, Texas – in an area with one the highest densities of EVs in the country. They randomly selected 30 homes, half of which were also participating in a trial on time-of-use (TOU) pricing.

As you can see in the image below, some previous models had suggested that a sudden spike would occur at the end of the workday, which is a time of high electricity demand on hot summer days. The results of the trial tell a very different story: charging is much more spread out throughout the day, with the peak occurring late at night – when demand is lowest.

While this may not come as much of a surprise to EV owners (raise your hand if you always charge for exactly 3 hours at exactly 5 pm), it is helpful in giving system operators an idea of what to expect as EV ownership ramps up.

A few of the specific conclusions of the report bear repeating:

  • For the TOU group, charging during peak hours (3-7 pm) was even lower: about 22%
  • For the TOU group, telematics systems such as Nissan’s CarWings played an important role in time-shifting their usage.
  • The average weekday charging time was just under 2 hours, corresponding to about 20 miles of driving.

So, EVs are not the enemies of the power grid and, with TOU pricing, can even help to fill in the nighttime lull in electricity demand.

Source: Pecan Street Research Institute

Categories: Charging, General


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16 Comments on "Pecan Street Project: EV Charging Not Likely to Stress Grid"

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The study is is worthless, because they had chosen only people with slow charging EVs. For example, the Renault Zoe can be charged even at home with 22 kW, which means the entire charging will not be stretched through the night, it will be completed right inside the peak hours, if no delay timer is used.

Did you miss that there is a Tesla there that can charge up to 20kW? Sure the Volts and Leafs that are there usually have the 3.3kW charger. But i think the study is pretty good anyway.

_one_ Model S and no word about what charing station he had used, maybe just the standard 110 V EVSE?

This is not representative for future EVs.

Then I guess you missed the Southern California Edison electric car study from 2 months ago. SCE territory is where 12,000 plug in vehicles reside. They found that about half of all plug in owners charged with the 120V cable. That is a much bigger sample than this little city study. And they found that most people charged during off-peak hours at night.
Even if they all used level 2, they won’t all start charging at the exact same time. So i think you are worrying too much. And the people in this city study only charged for 3 hours at most, so they didn’t go very far.

You also missed the point about Time of Use rates. A lot of people will chose to charge at off-peak times because the cost of electricity changes dramatically. On a flat rate I would charge as soon as I got home. On the TOU rate I only charge late at night. I’d rather spend $.10/kWh than $.39/kWh. Most people feel the same.

Many states don’t have off peak tariffs or the price difference is very small.

That will most likely change as more people buy EVs. Regions that start to have issues with peak time charging will adopt rating systems used by regions that have a more workable design.

Price difference in california is one of those small ones. going from 13cents to 10 cents. Ohhhhh!

Um, NO. The PG&E (most of Northern California) EV rate is $0.098 Off Peak. Summer Part-Peak is $0.206 and Summer Peak is $0.376/kWh. This plan is not tiered. The normal rate plan (E-1) does not consider time of use, but it has tiers. Those rates go from $0.132 to $0.352/kWh depending on how much electricity you use per month.

“if no delay timer is used”

I think this makes your criticism even more worthless. Why on earth would mainstream EV use involve charging inside peak hours?

Not everyone owns a house with private parking lot. Million people can only use public parking lots near their flats and they will have to charge after work, using public quick chargers.

The flats with solar canopies? Seriously, you’re just looking to make arguments. Hurdles will be overcome and not everyone will drive a personal EV. The real solution is mass transit and smart city design.

Dr. Kenneth Noisewater

BTW, the Volt has its own built-in ‘delay timer’ that you can program for weekly ToU plans.

Since I actually LIVE in the city in question I can tell you they have 220 chargers. The city provides any Austin Energy user a 50% rebate for installation costs of an L2 charger, coupled with the federal 30% rebate, and it is cheaper to get a L2 over even a L1 replacement cord and if you consider the higher efficiency of the L2, eventually pays you back. For my Energi, it is 3 times slower to charge on L1 and takes on 10%ish more charge.

Ford had built in and smart phone controllable delay charging also.

This seems to be very focused on suburban/home owning drivers.

These constitute only a share of the market. In urban locations such as San Francisco, LA, San Diego, etc. the % of single family homes that have their own driveway/garage and can control their Electric rate plane is MUCH MUCH lower. In San Francisco for example 67% of the the population rents. In LA it’s 50%, etc. Overall in CA it’s about 41%, nationwide a bit lower.

Studies such as these are needed but study of the real world of renters are needed as well.

Renters do cause some head-scratching problems.

I’ve concluded the cheapest thing to do is to have a certain area reserved for EV’s that are charging, and provide a low-cost swipe card to the tenent. Overall, the system would be slightly profitable for the landlord/HOA so that they’d have an incentive to provide the charger space. This works for Large complexes. Smaller 4-12 banger apartment bldgs have to be approached individually with what the landlord can provide. A spot next to the building with a lockable 110 volt outlet on this tenant’s meter is one relatively low cost solution. But, it has to be brokered with the landlord. Perhaps the landlord will go for a 220 volt EVSE if the tenent pays for the EVSE himself.