The western US is suffering from a major heat wave that may result in gradual power outages and warnings not to charge electric cars in the afternoon. With California also mandating that all cars be electric by 2035, a common meme often bandied about by EV opponents, the idea that the grid can’t handle it, has resurfaced.
At the same time, it is true that we are planning highly renewable grids, but the key renewables, solar and wind, are intermittent, time of day and weather dependent.
It turns out that these two problems can actually cancel each other out, and when combined with some other technology, it won’t be a problem.
You need more energy, not necessarily more power
It is true that to make all cars electric, we need to generate more electricity. Grid capacity can be measured both by total annual energy production and by maximum output, and these are different things. Energy is a commodity like gallons of gasoline or kWh. Power is the instantaneous energy delivery, the amount of energy you can deliver per second.
In the grid, energy demand and supply fluctuate throughout the day. At night they are low, but on warm days the demand rises steadily as the day goes on and gets warmer, causing the need for additional air conditioning. AC power is the primary driver of peak demand on the grid. Demand tends to peak around 6pm, but remains strong until 9pm and then declines into the night. There is no peak in cooler times when it is the hottest, so there tend to be two (much lower) peaks during the day. The network has capacity for performance at any given moment. This changes during the day due to renewables, but the main aim is to ensure that between 4pm and 9pm, when demand is highest, we have enough supply capacity to cover it. So we spend money to build power plants and transmission lines to provide that supply.
The chart shows California demand and supply during the heat wave, September 3, 2022. Total supply was over 55gW, so there was quite a bit of extra, but during the 3pm to 9pm peak, it’s over 40gW.
The supply is still available for the rest of the day. We can only turn on all the power plants in the late afternoon, but we paid for them and can turn them on at other times if we want. Some power plants, such as nuclear power plants, have to run all day, it is difficult to shut them down. Efficient natural gas plants take time to heat up and cool down, but we can shut them down when they’re not needed. Hydroelectric plants can be turned on and off as needed. Of course, solar power plants only produce electricity during the day and the most when it is sunny.
Cars can be charged at any time of the day. The average American car drives less than 40 miles in a day, which means it can usually go 5 days without a charge if needed, but it can definitely choose when to charge if it can be plugged in. Most connect at night, when there is the most excess power capacity on the network and power is cheapest. In the future, more of them will be involved in the work, but those cars will have excess capacity until about 2:00 p.m. A very small number of cars on the road will need to charge late in the afternoon and will be charged a surcharge.
People who didn’t get it found it ironic that California announced a plan to go all-electric by 2035 in the same week that a heat wave reminded them not to charge between 4pm and 9pm. This was misreported as they were asking people to avoid charging their cars, but in fact the advice not to charge during peak hours is standard good advice in all circumstances, not just during heatwaves. No one in California has been left with a dead car due to this shortage, as it is only a peak in demand for strength not energy in the tips.
(It should be noted that despite the warnings, California’s grid operator has never had to implement rolling blackouts. Simple text messages asking people to reduce power have worked surprisingly well.)
Energy is what does useful work like moving cars and cooling homes. It is measured in units such as kilowatt hours (kWh) or even gallons of gasoline. Power is the rate of energy flows, measured in kilowatts or horsepower. Your car may need a gallon of gas to go 30 miles, or 7.5 kWh, but it needs more horsepower to do it faster. Especially since kW and kWh sound so similar, people confuse them.
We don’t need to increase the power of the grid to charge all the cars, but it will need to generate more power. Even if all new cars will be electric in 2035, most petrol cars will leave the road in 20 years. Today, Americans drive about 3 trillion miles a year (half a light year!) if they did it all in cars like Tesla
The Model 3 would need 750 terawatt hours (tWh) more per year. In 2020, the US produced 4,000 tWh, so that’s about a 20% increase — though not until around 2050. It’s more than that because there will be trucks that use much more energy per mile and other less efficient cars. there will be more cars and more driving, but that gives you an idea of the amount of extra energy needed. (We also want to move gas home heating and water heating from fossil to electric heat pumps, which is another discussion.)
The US grid has already increased its overall energy output by 20% over the past 30 years, so this is certainly something that was previously done without much effort. As the increase may be greater, some extra effort may be required. (Maybe not, we’re still getting better at efficiency and many of our appliances and things like our light bulbs use a fraction of the energy they used in the past.)
Even though we need 20% more energy, we don’t need much more energy because of electric cars. We may need more energy for other things—particularly population growth—or we may need less as we become more efficient. The new plants offer more power and more energy, albeit in different ways. If we only planned to burn more coal and gas, we could actually get more power from existing plants by burning more fuel, but that’s not our plan, so we’ll need more renewable plants. However, because of the cars, we won’t need another grid.
This extraordinary effort will come mostly from renewable sources, especially solar. It is not for any environmental reasons. Solar power is the cheapest type of new power plant to build today. 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 at the lowest price and you can choose when you use it, solar is the only power plant that is based solely on price – although zero emissions are certainly nice.
While it is clean, quiet and easy to operate, its downside is that it only supplies power in sunny weather. In fact, if you wanted to generate 24 megawatt hours per day, you could do it with a 1 megawatt conventional plant running all day, but with solar you might need a 6 megawatt plant and you would only get the power during the day unless you also had storage. But this 6 megawatt solar plant would cost less per unit of energy than a 1 mW gas, coal or nuclear plant.
To solve this problem, you need to find a large load that can interrupt the supply of renewable energy when it says so – when the sun shines or the wind blows.
This is exactly the type of load batteries, i.e. EVs. As long as the car is plugged in, it will take energy when there is an excess and not take it when there is a shortage. Very few other loads are as flexible. For every other load, you need power when you need it, but with a battery, you draw it at a different time than when you use it. One of the other burdens like this is the filtration of the pool water – just filter it enough every day, it doesn’t matter when.
Heating and cooling
The biggest load on the electricity grid and the cause of peak demand is cooling, and once we switch heating from fossil fuels to heat pumps (air conditioning vice versa) it will also become a big load. However, heating and cooling can also postpone their need, if we use a gearbox designed for this. That’s because you can store heat (or cold) in the cheapest “battery” of all – water.
Newer advanced air conditioners know how much air conditioning will be needed later that day. During the night and morning, they cool and freeze the water in insulated ice tanks. They do this when electricity is cheap and plentiful, and when the temperature is cooler and requires less effort. Later, when energy is scarce, they use this ice to cool buildings. Our temperature predictions are now very accurate, so computers can control this whole process to be fast and efficient. The energy will come either at night (when demand is low) or in the morning (when it is still cold and there is a large solar surplus.) The solar surplus will be so large that all loads that may move over time (such as batteries, cooling and heating ) will remove the excess in the morning. Renewables need storage, but that storage will be batteries already in cars and tanks for ice or (for heating) hot water. There will also be other types of storage (pumped hydro and batteries and other methods), but we will need much less than if we were to stick with our old air conditioners.
As such, much of the future renewable grid problems can be solved with electric cars and ice. Note that this does not include cars serving as batteries through a technology called “vehicle to grid”. This can be done once the batteries get a super-long life, but it doesn’t make sense when expensive car batteries run out during operation, unless the energy can be sold at very high spot prices during grid congestion.
(Ice storage for cooling and heating has been surprisingly slow to take off. According to Mike Hopkins, former CEO of Ice Energy, the oldest company in the space, people who install air conditioning simply aren’t used to the new stuff, and even basic government mandates don’t allow it enough (quickly. He thinks the law should start requiring storage—not necessarily ice—for heating and cooling in new construction, which will solve the problem of peak demand.)
The problem with Solar is that it generates electricity on the Sun’s schedule, not yours. Electric cars need much more electricity, but they can receive it according to the solar schedule. These two problems cancel each other out. Add to that the ability of air conditioners, home heating systems, and hot water systems to produce and store heating and cooling and release it later, and it’s as if the problems were created for each other. Of course, this doesn’t solve everything — we’ll need other types of storage, and probably more wind, nuclear and geothermal. And we will be using our natural gas power plants on the highest peaks for some time to come. Some people think we’ll even use batteries in EVs to sell power back to the grid at peak times to prevent this. In the graph above, the yellow solar line will be much higher – actually higher than peak demand, but that creates a big problem at 7pm when the sun sets and suddenly all that peak power has to come from non-solar power.
The way electric vehicles are saving the grid is that they allow us to build tons of cheap, green solar capacity and then give us a place to put all that extra solar power from morning to 3 p.m.
We will also need to install many more charging points where cars park from 8am to 3pm, which is a mix of workplaces and homes. While night is the best time, cheap solar surplus will be in the morning. There is still a lot to be done, but electric cars, with their flexibility in taking power, will be part of the solution, not part of the problem.