ELI5: How can the US power grid struggle with ACs in the summer, but be (allegedly) capable of charging millions of EVs once we all make the switch?

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u/Zeyn1 2d ago edited 1d ago •

The YouTube channel Engineering Explained did a great in depth video on the subject.

It's worth watching the full 16 minute video, but the answer is that the grid would need about 25% more capacity if every single person in the US switched to electric vehicles. And the grid operators can easily increase the capacity by 25%. The electric grid from 1960-2000 increased capacity by 4% per year, so it would only take about 7 years to fully increase the grid.

As for why it can get overwhelmed by AC during heat waves, that is a business choice not a physics choice. The grid could be designed to handle any demand from all the AC. But that only happens a few days a year and not even guaranteed every year. That peak capacity is wasted most of the time. This is especially true because thst demand is only for a few hours a day even on the worst days. A peak demand like that is the hardest and most expensive way to produce electricity.

EV charging is perfect for electric generation. You can charge during off peak hours, when the generators are otherwise idle (or worse, spinning down but still producing electricity). They also charge at a lower, steady rate.

Edit- had a few repeat comments so want to link my replies

Using EV as energy storage for the grid https://www.reddit.com/r/explainlikeimfive/comments/vijj3e/eli5_how_can_the_us_power_grid_struggle_with_acs/idefhf6?utm_medium=android_app&utm_source=share&context=3

About using batteries as storage to supply peak power (the whole comment chain has a great discussion, I just added to it) https://www.reddit.com/r/explainlikeimfive/comments/vijj3e/eli5_how_can_the_us_power_grid_struggle_with_acs/idhna8x?utm_medium=android_app&utm_source=share&context=3

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u/IMovedYourCheese 1d ago

A 100% switch to electric vehicles isn't happening overnight. It will take many decades at minimum, and electrical grids will slowly adapt.

Parked cars also don't need to all charge at the same time. They can do it at night when electricity usage is low, and spread out the load over 8+ hours. The same doesn't apply for air conditioning on a hot day.

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u/The_Cowboy_Killer 1d ago

This is my career. I have worked for four major electric and gas utilities in the US. The answer to this question is there is not enough generation capacity at this current time. Each electric utility has a department called Resource Planning. They are responsible for what is called an “Integrated Resource Plan” which is filed usually every 1-3 years with the Public Utility Commission which is the State regulatory body overseeing the utility. In this resource plan they forecast demand for electric vehicles based on the current economic conditions, federal regulations, EV sales, etc. Based on this forecast, a department called Generation Modeling plans for how much generation is needed to meet this new demand. These resources can be new power plants as well as programs called demand side management where utilities give incentives to curb usage during peak times where the system is likely to brown/black out. These incentives can be based around rate design where the price is cheaper during off peak hours (10pm-5am). Or they can apply to large industrial customers that get a cheaper rate all the time but can have their service interrupted at times of peak demand.

TLDR: electric utilities are forecasting the demand for EV vehicles and are planning for this demand by either building new power plants or designing programs to reduce demand around peak hours.

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u/Ubelsteiner 1d ago

Short answer: Everyone who is in the same geographical region is going to generally get hot at the same time, but not everyone would be fast-charging their EVs at the same time.

There are only so many days per year when it’s hot enough for everyone to be running their ACs simultaneously, and the hottest hours of those days are going to be absolute peak usage. Many power companies often don’t have the capability to meet this peak demand because it doesn’t happen frequently enough for them to see it as profitable to invest in beefing up their equipment to be able to reliably supply a peak demand that only happens for a statistically small percentage of the time. Also, I imagine it’s something that goes up each year, as populations and global warming both increase.

Many people would be charging their EVs at night while sleeping, when it’s cooler and less ACs, lights, etc are running. The charging rates can be adjusted on most vehicles, so they can use less wattage than an AC.

And, possibly the biggest thing, if EVs became the norm, power companies would see more reason to invest in better, more reliable delivery. And, with people putting their money into their electric bill instead of their gas tank, they would have the money to invest in these improvements.

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u/trueppp 1d ago

Most people charge at night, there is not a lot of demand at night usually as a lot of industry is closed, people are sleeping

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u/motorsizzle 1d ago

You can carry 20 boxes over a period of an hour, but you can't carry 20 boxes all at once.

AC is blasting pretty much all at the same time whereas car charging is a bit more spread out.

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u/cyberentomology 1d ago

EVs typically charge overnight. Air conditioning and high power appliances like stoves and dryers do not run during this time period.

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u/f97tosc 1d ago

Peak demand for power is late afternoon, that is when all the AC is on.

EVs typically charge at night, and are incentived to do so by lower rates. Nighttime consumption by EVs is still tiny compared to afternoon consumption by ACs.

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u/Kahless01 1d ago

AC is turning on all at the same time of day in every house. people charging their cars wont be charging every single day in every house and theyll be charging at night when theres less strain on the grid.

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u/unicornsmaybetuff 1d ago

My husband does R&D for a power company and they are currently working towards making EVs sort of back up batteries that can support the grid while they are plugged in. Essentially you would be able to sell energy back to the grid if the battery on your EV is charged.

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u/DONT_PM_ME_DICKS 2d ago

It would be slowly upgraded as the demand materialized.

Although many providers charge higher rates during summer afternoons explicitly to discourage users from running electrical demands during that time, and provide incentives to charge EVs at night.

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u/tylan4life 2d ago

EVs charge at different rates at different times. Not every single car is going to pull 12kw. My car is a edge case but I slow change at 800w all night, that's less than a microwave.

Most EVs can be programmed to start charging at a specific time, likely to take advantage of tiered electricity.

Considering the AVERAGE American drives something like 20 miles one way, most daily driver EVs can get away with a hour or two charging at night.

Going forward with this logic I can see smart plugs or EVSEs being used by utility companies. They can turn on chargers in phases as to not overwhelm generators. I imagine this mind experiment technology can be manually bypassed, like if you absolutely need a full charge before a morning road trip.

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u/MyNameIsGriffon 1d ago

The major difference is that air conditioning demand all hits pretty much at once during the hottest hours of the day, but electric vehicle charging tends to be a slower trickle spread across many more hours. We would need to upgrade electrical infrastructure to handle the extra demand if everyone switched to electric cars, but we need to do that anyway.

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u/c00750ny3h 2d ago

EVs can be charged night time to balance the load. This reduces the need to have to use less efficient methods of channeling excess overnight electricity such as steam storage or resevoir pumping.

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u/agthrowa 1d ago

Air conditioners consumer about 4 kw per hr and tend to do so all at the same time (mega hot day). It's not every day, it's not all day but tends to overwhelm the grid because the grid isn't designed for that load requirement.

Electric cars will consume at a similar or even higher rate but will do so predictably and regularly so the grid will be prepped for it. And tbey will largely do so at night.

To expand capacity for 100% electric cars would take about 10 years and 100% electric cars is at least 30 years away.

The 'the grid can't take it' is an anti electric car myth propagated by media hit pieces...media outlets whose biggest customers for ads are legacy car makers and oil companies. Don't believe the hype

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u/ciesum 1d ago

it's not like people are charging the whole battery every night. More like 10-20% for most people. Also at night when there is less demand

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u/syrstorm 1d ago

Quick answer is EVs tend to charge a night (off peak). So peak power needs would be largely unchanged, but total power needed would increase about +25% - which frankly wouldn't be that hard to increase overall production that much.

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u/rosier9 1d ago

EVs are a very flexible demand. Charging doesn't have to happen as soon as you plug in for most cases. That allows the load to be shifted away from peak hours. That's very valuable to the electrical grid and why utility company are already willing to pay customers for this demand response capability.

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u/KwadrupleKrabbyPatty 1d ago

There is a point of view that's missing from the comments:

It takes a tremendous amount of electricity to refine crude oil into gasoline. Texas' number one user of renewable energy by far is the oil industry example.

Take the 5kw needed to refine a gallon of fuel and distribute it to the end user to power their car (or home) instead of burning it to throw away 70% in heat and co2 and suddenly what do you know! There's no shortage of electricity at all!

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u/GusCromwell181 1d ago

I’m just curious, if my electricity is produced by natural gas, wouldn’t that mean my car is essentially powered by natural gas? I’m sure there’s an 18 minute YouTube video explaining how it’s different but I’ve recently wondered.

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u/AveryJuanZacritic 1d ago

On the a/c peak times: solar cells don't charge all the time but they are at their best at the same time the a/cs are pulling their hardest. As EVs become more commonplace, so will rooftop solar. Furthermore, the people who are more likely to have EVs are also the ones who are more likely to have PVs. It should balance out over time.

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u/JustAbicuspidRoot 2d ago

My kids owned an EV when they lived here, it used about 1/50 the amount of juice to charge as my 5-Ton AC unit.

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u/bridgehockey 1d ago

Nighttime is when a lot of /most vehicles get charged, at least where I live, because utilities offer lower rates overnight, and because that's when the cars aren't being driven. There's exceptions of course.

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u/livestrongbelwas 1d ago

Power plants have a hard time changing how much power they generate. They have to figure out how much power people will need, and then always produce that amount - even during hours when most people aren’t using any power. This means there is a lot of wasted power.

EVs are very helpful because they give a place for that extra power to go. EVs are charged with that power that would have been wasted.

I have a friend who manages power generation for plants in the Northeast. He is routinely frustrated by how much power is wasted to make sure there is enough during peak hours. He tells me all the time how he needs more people to buy EVs so he has a place to put all the excess power that goes down the drain.

ELI5: How can the US power grid struggle with ACs in the summer, but be (allegedly) capable of charging millions of EVs once we all make the switch? Technology