EVs Optimize the Grid

Even people as smart as Neil DeGrasse Tyson get it wrong because they only look at the numbers and ignore the rhythm! @Aventador, a professional in the industry, had this to say at SA:

The grid is like a bus that never turns off. Yes, it hauls passenger’s during the day but at night little to no demand. That energy is wasted and thrown away as the bus runs just as it did during the day. The EV being a mass storage device takes that wasted energy and stores it for future use. Uses that can even power the home in storms as the F150 Lightning can and most future EV`s will be capable of. [emphasis added]
Link to the comment:

I have read elsewhere that the price of electricity has ben falling for this very reason.

The Captain

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Actually, it’s the opposite. See the below:

“Once 30 or 40 percent of cars are EVs, it’s going to start significantly impacting what we do with the grid,” said Ram Rajagopal, a professor of civil and environmental engineering at Stanford University and one of the study’s authors. Even if drivers wait until after peak hours and set their cars to charge at 11 p.m. or later, they will be using electricity at exactly the time when renewable energy is not readily available. That could lead to increased carbon emissions and a need for more batteries and storage in the electricity grid.

One solution, the researchers say, is if more EV owners shift to daytime charging, charging their cars at work or at public chargers. If electric cars are charged in the late morning and early afternoon, when the grid has excess solar capacity that’s not being used, there will be less pressure on the electricity system and less need for storage. According to the study, under a scenario where 50 percent of cars are electric, a shift from mostly home to a mix of home and work charging could almost halve the amount of storage needed on the grid

That’s because the grid isn’t like a bus that never turns off. It’s like a fleet of busses that never turns off. Just like there are different amounts of passengers at different times, there are different amounts of busses at different times. There are (currently) a lot fewer busses at night than there are during the day. That’s going to intensity. As we move to more and more solar, there’s going to be a lot more busses during the day.

EV charging at night would optimize the grid to the old way of providing electricity. It would make it more useful to have large baseload dispatchable power plants (like coal and natgas plants) that are on all the time. But we’re moving away from that model, towards a more intermittent supply that generates most of its power during the afternoon as solar production peaks. Which makes night-time charging a problem, not a solution. We need more daytime charging, not at night.



We will need more daytime charging in the future. Not now while most of our electricity isn’t renewable, and a lot of it is “base”. But it’ll all work out fine over time because as EVs get more popular, more charging infrastructure is being built out, especially at workplaces and shopping places. Also if the WFH thing remains, many people with EVs will charge during the day anyway. That is assuming electric utilities set the rates rationally (many people charge at night because the rates are lower at night).


Yeah, but we’re talking about the future. Not now, while nearly every car in the country is still an ICE vehicle. By the time we get enough EV’s in place to actually have any kind of impact on the grid (optimizing or not), we’re also going to be in a place where solar generation is big enough to present these types of issues for the grid.

Arguably, we’re there already in California - on both sides of the equation. Nearly half of all EV’s are sold in California, and California has been trying to deal with “duck curve” problems with the daily time distribution of electricity generation since about 2017. California’s daily low for grid/base demand used to be about 4:00 a.m. (as you would expect) - now it’s noon, when solar generation relative to demand peaks.


Since we can expect some rough correlation between EV uptake and the solarization of the grid by state, we might see that type of pattern continue. So it’s not going to be very common that you have lots of EV’s (again, enough to matter) and an old-fashioned grid at the same time.

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In the OP I was talking about the daily rhythm but there is also the longer term rhythm, how wind, solar, storage, and transmission develop. The difficulty with renewables is intermittence. The solution for intermittence is two fold, storage and transmission. Tesla’s second line of business is storage at three levels, household (Powerwall), business, and grid (Megapack).

As EV adoption grows and nighttime charging grows so will the cost of nighttime charging which will encourage people to also use daytime charging when convenient. Products and services like Virtual Power Plants and Autobidder should be a big help in making the transition smooth.

Renewables have rhythm and users will learn to dance to its beat.

The Captain


I suspect it isn’t EVs so much that is affecting this timing yet (even CA still has vastly more ICE vehicles). There is probably something else involved, maybe CA shifting of renewable sourcing in order to show good renewable numbers?

Besides, if they wanted to encourage charging at noon, they can simply lower the electric rates at that time. Just like 58 cents/kWh encourages people to not use [as much] electricity between 4pm and 9pm, a rate of 5 cents/kWh at noon would encourage people to charge at noon instead of overnight. But no, instead CA charges (PGE at least) the same at noon as they charge at midnight, so people choose to charge at night when it is more convenient. However, more and more workplaces are adding chargers, free or near-free ones, so some people are choosing those now, and therefore do charge during the day.

I have 2 EVs. One charges almost entirely at a workplace that has free chargers. The other, my primary vehicle, charges mostly during the day, but basically whenever convenient to me, because my electric rate is the same 24/7. In fact, my car is charging right now as the sun shines brightly, and has 50 minutes to go.

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That’s absolutely correct. I didn’t mean to imply otherwise. It’s the solar that’s causing their issues. Solar generation peaks around noon, and stays high until 3-4 p.m. But peak demand happens between 5-9 p.m., when everyone comes home after work and turns on their ovens and TV’s and A/C (in the summer). You have this huge evening ramp away from solar and onto baseload.

The point to captainccs is that EV’s don’t help if they’re charged at night. They don’t optimize the grid. Any state that relies on solar for a non-trivial amount of generation is going to be put in a worse situation if there’s a lot of EV’s doing night-time charging. And given the rough correlation between state policy encouraging transition to solar and encouraging EV’s, most states are going to get to non-trivial levels of solar generation before they get to non-trivial levels of EV’s.

As you suggest, one of the recommendations of the experts cited in the WaPo article was for utilities to respond by moving their “off-peak” rates to early daytime, to encourage more daytime usage.

Does CA really not have different rates based on time of day?

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I think that it might be different than this based on which season or month it it.
Also, it may depend on the weather. Here in CA we’ve had lots of cloudy days and rain and will for the next week as well. So not a lot of good excess solar for daytime charging.

The solution is for connected cars and the ability to set a minimum charge level and a nice to have charge level based on over the air pricing info.



Most of CA does as far as I am aware.

I’m going to guess that if cars get the ability to distinguish between 1,000,000,000 possible scenarios as you “turn left” on a highway, that they will be able to reasonably distinguish the optimum time to charge, and will wait for a lower priced charging tier unless they are below a certain safety threshold or unless the owner “commands” them to charge fully (perhaps because he has a big trip coming up.)



I remember in the not too distant past, California electric utilities had a well-publicized slogan, “Give your appliances the afternoon off.” That was the daily peak in demand on the grid. Emphasis on “was.

Now they’re begging us to use optional electricity mid-day to early afternoon. And that is reflected in our time of use pricing. The highest residential prices are currently from 4pm to 9pm.


As documented in the link below from San Diego Gas & Electric. Scroll down to the TOU-DR1 pricing plan (TOU = Time of Use) and click on the down arrow.


On-Peak price: 44 cents per kilowatt-hour (4 pm to 9 pm)
Off-Peak: 38 cents ( 6 am to 4 pm and 9 pm to midnight)
Super Off-Peak: 36 cents (12 am to 6 am)

So, the very cheap and affordable lowest price electricity is 36 cents per kwh. It should be noted that the average price of residential electricity in the US is 15.1 cents per kwh. SDG&E’s cheapest rate is still more than twice the national average.

On the other hand, gasoline prices are also high in California, so it is still cheaper to charge an EV than to fill up a petrol tank for a standard ICE.

  • Pete

That’s fine for late afternoon/evening influence. But CA (PG&E at least) charges the same at noon as they charge at midnight, so you may as well charge (or do laundry, etc) at midnight when you know the car will be parked there for a few hours. Want to encourage use at noon? Adjust the price accordingly! “Begging” only works to a very limited extent.

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EV’s, not AV’s. These aren’t necessarily cars that can drive themselves, but rather the millions of ordinary electric vehicles that will be hitting the roads over the next several years.

And even an AV can’t charge unless it’s at a station. So if someone has access to a charger at home, but not at work, they’re going to be charging at night no matter how smart the car is. Because of the decisions made by the human.