EVs Won’t Overload The Power Grid, In Fact EVs (And Ice) Are Its Salvation

The U.S. west is suffering a major heat wave which may result in rolling blackouts and reminders not to charge electric cars in the afternoon. With California also ordering that all cars by 2035 be electric, this has resurfaced a common meme often spoken by EV opponents, the idea that the power grid can’t possibly handle this.

At the same time it’s true that we plan a highly renewable grid, but the key renewables, solar and wind, are intermittent, dependent on the time of day and the weather.

It turns out these two problems can actually somewhat cancel one another out, and combined with some other technologies there’s not going to be a problem at all.

Need more energy, not necessarily more power

It’s true that for all cars to go electric, we need to generate more electrical energy. Grid capacity can be measured both in total annual energy production, and also by maximum power, and these are different things. Energy is a commodity like gallons of gasoline or kWh. Power is the instantaneous delivery of energy, the amount of energy you can deliver in a second.

On the grid, power demand and supply fluctuate during the day. They are low at night, but on warm days, the demand keeps climbing as the day wears on and it gets hotter, causing the need for more air conditioning. AC is the primary driver of peak demand on the grid. The demand tends to peak around 6pm but is still strong until about 9pm and then it declines into the night. At cooler times there is no peak when it’s hottest, so there tends to be two (much lower) peaks in the day. At any given time the grid has a power capacity. That fluctuates during the day due to the renewables, but the key goal is to make sure that from 4pm to 9pm, when demand is highest, we have enough supply capacity to meet it. So we spend money to make power plants and transmission lines to provide that supply.

The chart shows California’s demand and supply during the heat wave, on Sept 3, 2022. Total supply was over 55gW, so there was a fair bit extra, but during the peak from 3pm to 9pm, it’s over 40gW.

The rest of the day, the supply is still available. We may only turn on all the power plants in the late afternoon, but we’ve paid for them and can run them at other times if we want. Some plants, like nuclear plants, have to run all day, they are hard to turn off. Efficient natural gas plants take some time to warm up and cool down, but we can turn them off when not needed. Hydro plants can be turned on and off as desired. Solar plants of course only generate power in the day, and the most when it’s sunny.

Cars can charge any time of day. The average US car drives less than 40 miles a day, which means they can usually go 5 days without charging if they needed to, but they can definitely pick when they will charge as long as they can plug in. Most plug in at night, when there is the most excess power capacity on the grid, and power is the cheapest. In the future, more will plug in at work, but there will be excess capacity until about 2pm for those cars. A very small number of cars on road trips will need to charge in the late afternoon, and they will pay a premium for it.

People who didn’t understand this thought it was ironic that California announced the plan to go all-electric by 2035 the same week as a heat wave made them remind people not to charge from 4pm to 9pm. This got mis-reported as them asking people to avoid charging their cars, but in fact the advice not to charge at peak is standard good advice at all times, not just in heat waves. Nobody in California found themselves with a dead car due to this shortage, because it’s only a demand peak for power, not energy, at the peak times.

(It should be noted that in spite of warnings, the California grid operator never had to do rolling blackouts. Simple text messages asking people to reduce power did surprisingly well.)

A refersher:

Energy is what does useful work, like moving cars and cooling homes. It is measured in units like kilowatt-hours (kWh) or even in gallons of gasoline. Power is the rate energy flows, measured in kilowatts or horsepower. Your car might need a gallon of gas to go 30 miles, or a 7.5 kWh, but it needs more horsepower to do it faster. Particularly because kW and kWh sound so similar, people get them confused.

More Energy

We don’t need to increase the power of the grid to charge all the cars, but it will need to produce more energy. Even if all new cars in 2035 are electric, it won’t be until about 20 years after that before most of the gasoline cars leave the road. Today Americans drive about 3 trillion miles per year (half a light-year!) If they did all that in cars like the TeslaTSLA
Model 3, that would need 750 more terawatt hours (tWh) per year. In 2020, the USA generated 4,000 tWh so this is an increase of about 20% — though not until around 2050. It’s more than that, because there will be trucks which use much more energy per mile, and other less efficient cars, and there will be more cars and more driving, but this gives you a back-of-envelope idea of the amount of extra energy needed. (We also want to move gas heating for homes and hot water from fossil to electric heat pumps, which is a different discussion.)

The US power grid already increased in total energy output by 20% in the last 30 years, so this is certainly something that’s been done before without any special effort. Because the increase might be larger, some special effort may need to be made. (Maybe not, we keep getting better at being more efficient, and many of our appliances and things like our light bulbs use a fraction of the power they used in the past.)

While we need 20% more energy, we don’t need much more power because of the electric cars. We may need more power for other things — particularly population growth — or we may need less when we get more efficient. New power plants offer both more power and more energy, though in different ways. If we planned to just burn more coal and gas, we actually could get more energy from the existing plants by burning more fuel, but that’s not our plan so we will need more renewable plants. We won’t need more grid because of the cars, though.

This extra effort is going to come mostly from renewable, especially solar. That’s not for any environmental reason. Today solar power is the cheapest type of new power plant to build. When you look at the total cost per kWh from any type of plant, solar is the winner — and it’s getting cheaper every year. If you just want energy for the lowest price, and you can pick and choose when you use it, the solar is the only plant to build simply on price — though the zero emissions are certainly nice.

While it clean and quiet and easy to operate, its one downside is it only gives power when it’s sunny. In fact, if you wanted to generate 24 megawatt-hours per day, you could do that with a 1-megawatt ordinary plant running all day, but with solar you might need a 6-megawatt plant, and you would only get your power in the daytime, unless you also had storage. But that 6 megawatt solar plant would cost less per unit of energy than the 1 mW gas, coal or nuclear plant.

To solve that problem, you need to find a big load that can take the intermittent power delivery of a renewable plant when it’s told to — when the sun shines or the wind blows.

That’s exactly the type of load batteries, which is to say EVs, are. As long as a car is plugged in, it will take power when there’s a surplus, and not take it when there’s a shortage. Very few other loads are that flexible. For every other load, you need the power when you need it, but with a battery you take it at a different time than you use it. One other load like this is filtering swimming pool water — you just need to filter enough every day, it doesn’t matter when.

Heating and Cooling

The biggest load on the electrical grid, and the cause of peak demand, is cooling, and as we switch heating from fossil fuel to heat pumps (air conditioners in reverse) it will also become a big load. But heating and cooling can also shift their need, if we use gear designed for that. That’s because you can store heat (or cold) in the cheapest “battery”of all — water.

Newer advanced air conditioners know just how much air conditioning will be needed later that day. During the night and morning, they chill and freeze water into insulated tanks of ice. They do this when the electricity is cheap and plentiful, and when the temperature is lower and it takes less effort. Later, when power is scarce, they use that ice to cool buildings. Our temperature forecasts are now very accurate so computers can control this whole process to make it fast and efficient. Power will either come at night (when demand is low) or in the morning (when it’s still cool and there’s a big surplus of solar power.) The solar surplus will be so large that all the loads that can move in time (like batteries, cooling and heating) will take the surplus in the morning. Renwables need storage, but that storage will be the batteries already in the cars, and the tanks of ice or (for heating) hot water. There will also be other types of storage (pumped hydro and batteries and other methods) but we’ll need a lot less of that than we would if we stick with our old air conditioners.

As such, a large fraction of the problems of a future renewable grid can be solved with EVs and ice. Note that this does not involve the cars serving as batteries through what is called “vehicle to grid” technology. That may be done once batteries get to be super-long-lasting, but it doesn’t make sense when expensive car batteries get used up as they operate, unless power can be sold at very high spot-prices during grid overload.

(Ice storage for cooling and heating has been surprisingly slow to be deployed. According to Mike Hopkins, former CEO of Ice Energy, the earliest company in the space, people who install air conditioning are just not used to new things, and even basic government mandates aren’t making it happen fast enough. He believes that the law should start demanding storage — not necessarily ice — for heating and cooling in new construction, and this will solve the peak demand problem.)

Solar’s problem is it generates power on the sun’s schedule, not yours. EVs need lots more electrical energy, but can accept it on the sun’s schedule. The two problems work to cancel one another out. When you add the ability of air conditioners, home heating systems and hot water systems to make and store heating and cooling and dispense it later, it’s like the problems were made for each other. Of course, this doesn’t solve everything — we will need other types of storage, and probably more wind, nuclear and geothermal. And we’ll still use our natural gas plants for some time to come at the top peaks. Some people think we’ll even use the batteries in EVs to sell power back to the grid at the peak to avoid that. In the chart above, the yellow solar line will get much taller — in fact taller than the peak demand, but that creates a big problem at 7pm when the sun goes down and suddenly all that peak power has to come from non-solar.

The way that EVs are the salvation of the grid is they let us build a ton of cheap, green solar capacity and then give us a place to put all the extra solar output from morning to 3pm.

We’ll also need to install a lot more charging plugs where cars park from 8am to 3pm, which is a mixture of workplaces and homes. While night is the most convenient time, the cheap solar power surplus will be in the morning. There is still much to be done, but EVs, with their flexibility at taking power, will be part of the solution, not part of the problem.