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Electric Vehicle Charging Requires Significant Power Grid Upgrades

Electric Vehicle Charging
Electric Vehicle Charging

Last year, some 50,000 electric vehicles were sold, most of them in California. This is good news for the California air, but not so good news for the California power grid.

Now, there is enough capacity to handle the additional load of charging electric vehicles, but not in individual neighborhoods. For example, a typical neighborhood grid in California, might have up to ten houses on it. Even at peak usage during the hot afternoon sun, when air conditioning demand is highest, one house might only draw 2kW. A Tesla Model S 85kWh owner, who installs the optional fast-charger on a dedicated line in his garage, can draw up to 20kW. On a neighborhood grid with ten houses, designed to peak at 30kW, this would overload the grid.

It’s just like in your home, while you may have an overall draw of 2kW on the main line running into the house, it’s not all on a single socket. Various circuits spread throughout the house, sot he load is spread out. Start the microwave, toaster, coffee maker, and electric grill at the same time on the same circuit, and you’ll blow a circuit breaker. No one wants to burn the house down for sake of breakfast. In the case of adding electric vehicle fast-chargers to the neighborhood grid, some upgrades will be necessary in order to prevent overloading.

Fortunately, according to some studies, many electric vehicle owners charge on regular 120V sockets, which isn’t as much of a load, and they also schedule them to charge at different times instead of just as soon as they come home from work. This kind of charging doesn’t impact the power grid as much. On the other hand, as more powerful electric vehicles chargers, such as the LII dual charger that a Tesla Model S owner might install on a dedicated line in his garage, become more popular, overloading, brownouts and blackouts also become a bigger threat.

The solution? If you don’t need to charge as soon as you get home, see if you can set your electric vehicle to be charged by the time you wake up. If you can charge on the 120V line sufficiently for the next day’s driving, maybe you don’t need to overload the grid with an LII charger. The best solution is to notify your utility provider that you’ve purchased an electric vehicle, as well as if you’re installing a fast-charger, not so they can charge you more, but so that your neighborhood power grid can be slated for the required upgrades.

Image © Tesla Motors

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  1. jpwhitehome LoneWolffe that’s fine, one man crying wolf doesn’t mean the wolf is hungry. one point of view could be perceived as alarmist, while another might be perceived as complacent. it’s good news that SoCal is on top of things. SoCal is also probably the most advanced in the country. I wonder what other operators are experiencing.

  2. LoneWolffe jpwhitehome In the land of hypotheticals, clearly if everyone started drawing 20kWh all of a sudden, it would have a large and negative impact on the grid. I don’t live in the land of hypotheticals, I’m a little more pragmatic. As another commentator pointed out the SCE report showed minimal impact (1%) to the grid infrastructure, and California is where Tesla’s are made. If there is anywhere on the planet where the impact of Tesla 20kWh home chargers is to be experienced, its California. Essentially your article raises alarm where there isn’t any evidence to support the alarm. Why raise alarm as to what ‘could happen’ vs what is actually documented as happening? The article title suggests significant utility upgrades are required, which flies in the face of the SCE report documenting minimal upgrades.

  3. jpwhitehome that’s good, but the question is “what if everyone suddenly bought an EV and installed non-smart fast-chargers?”
    if everyone installed a 20kW Tesla charger, that’d be a significant draw when everyone comes home from work and plugs in.

  4. Congratulations on grasping the worst case scenario for an EV charger and the best case scenario for a small and very efficient A/C Unit. 
    The EVSE for my LEAF draws about 3.3kWh. A 2-ton A/C Unit running on 240v draws, you guessed it 3.3kWh. That’s the size unit I have at my home if you wondered why I picked  2-ton unit. The A/C unit runs for more hours than my LEAF charges for. The impact of my LEAF is less than that of a A/C unit. This is in line with government numbers and predictions. 

  5. i know some of the chargers can be scheduled, but have they been integrated smart-charging yet? from my understanding, smart charging is connectivity between different charging stations to balance load, but i haven’t heard how much of that is online yet.

  6. Where did I say the sky was falling?who mentioned profits? Please, let’s stick to what I said, not some conspiracy theory that you have in mind. I’ll check my numbers again anyways.

  7. This news item is bogus. A home only using 2kW !?! No this piece is garbage, and has an agenda. This media source was paid to pump out this negative item. Don’t be shocked, may of them are.
    I have seen several of this ‘The sky is falling, the grid will explode … blaa, blaa, blaa’. It is only the latest effort but the forces that do not profit from plugins  (the term is used for both Electric Vehicles: EVs and plugin-hybrids: pih/phev). 
    The public should know this news item’s numbers are bogus, the point is moot/bogus, it was just pumped out to stir up and leave the public with negative emotions about plugins. Don’t let the media play/fool you.

  8. In addition to what johnrysf mentioned, the SCE report also mentioned that the high-current smartchargers you are worried about will delay recharging a vehicle until utility demand is lower. This use of “end-charge timing” allows multiple smart chargers connected to the same grid to load-balance their demand automatically, preventing brownouts.

  9. Southern California Edison (SCE) wishes to tell you that, for 20 years, they’ve been on the forefront of provisioning for EV’s, and they’re doing just fine, thank you. Specifically, providing for EV’s has added only 1% to their circuit upgrade workload.
    On 8/6/13, SCE published a white paper, ““Charged Up: Southern California Edison’s Key Learnings about Electric Vehicles, Customers and Grid Reliability”. SCE suggests that they are an expert in the area, as “currently, SCE customers lease or own more than 12,000 plug-in electric vehicles (PEV), which represent about 10 percent of national EV sales. Because California leads the nation in EV adoption, other utilities and stakeholders in the auto industry may find the information from the white paper useful.” You’ll find a link to the white paper at
    One of SCE’s six major findings is “SCE’s approach to managing plug-in electric vehicle-grid impact is meeting customers’ needs. Since 2010, of all the nearly 400 upgrades SCE made to (or identified for) circuits that serve plug-in electric vehicle customers, only 1 percent of that work was required due to additional power demands from plug in electric vehicles. The rest of the work was required under SCE’s regular infrastructure upgrade and maintenance schedule.”


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