As California rapidly boosts sales of electric cars and trucks over the next decade, the answer to a critical question remains uncertain: Will there be enough electricity to power them?

State officials claim that the 12.5 million electric vehicles expected on California's roads in 2035 will not strain the grid. But their confidence that the state can avoid brownouts relies on a best-case — some say unrealistic — scenario: massive and rapid construction of offshore wind and solar farms, and drivers charging their cars in off-peak hours.

Under a groundbreaking new state regulation, 35% of new 2026 car models sold in California must be zero-emissions, ramping up to 100% in 2035. Powering these vehicles and electrifying other sectors of the economy means the state must triple its power generation capacity and deploy new solar and wind energy at almost five times the pace of the past decade.

The Air Resources Board enacted the mandate last August — and just six days later, California's power grid was so taxed by heat waves that an unprecedented, 10-day emergency alert warned residents to cut electricity use or face outages. The juxtaposition of the mandate and the grid crisis sparked widespread skepticism: How can the state require Californians to buy electric cars if the grid couldn't even supply enough power to make it through the summer?

At the same time as electrifying cars and trucks, California must, under state law, shift all of its power to renewables by 2045. Adding even more pressure, the state's last nuclear power plant, Diablo Canyon, is slated to shut down in 2030.

With 15 times more electric cars expected on California's roads by 2035, the amount of power they consume will grow exponentially. But the California Energy Commission says it will remain a small fraction of all the power used during peak hours — jumping from 1% in 2022 to 5% in 2030 and 10% in 2035.

"We have confidence now" that electricity will meet future demand "and we're able to plan for it," said Quentin Gee, a California Energy Commission supervisor who forecasts transportation energy demand.

But in setting those projections, the state agencies responsible for providing electricity — the California Energy Commission, the California Independent System Operator and the California Public Utilities Commission — and utility companies are relying on multiple assumptions that are highly uncertain.

"We're going to have to expand the grid at a radically much faster rate," said David Victor, a professor and co-director of the Deep Decarbonization Initiative at UC San Diego. "This is plausible if the right policies are in place, but it's not guaranteed. It's best-case."

Yet the Energy Commission has not yet developed such policies or plans, drawing intense criticism from energy experts and legislators. Failing to provide enough power quickly enough could jeopardize California's clean-car mandate — thwarting its efforts to combat climate change and clean up its smoggy air.

"We are not yet on track. If we just take a laissez-faire approach with the market, then we will not get there," said Sascha von Meier, a retired UC Berkeley electrical engineering professor who specializes in power grids. The state, she said, is moving too slowly to fix the obstacles in siting new clean energy plants and transmission lines.

"Planning and permitting is very urgent," she said.

The twin goals of ramping up zero-emission vehicle sales and achieving a carbon-free future can only be accomplished, Victor said, if several factors align: Drivers must avoid charging cars during evening hours when less solar energy is available. More than a million new charging stations must be operating. And offshore wind farms — non-existent in California today — must rapidly crank out a lot of energy.

To provide enough electricity to meet total demand, California must:

Convince drivers to charge their cars during off-peak hours: With new discounted rates, utilities are urging residents to avoid charging their cars between 4 p.m. and 9 p.m. But many people don't have unrestricted access to chargers at their jobs or homes.

Build solar and wind facilities at an unprecedented pace: Shifting to all renewables requires at least 6 gigawatts of new resources a year for the next 25 years — a pace that's never been met before.

Develop a giant new industry: State officials predict that offshore wind farms will provide enough power for about 1.5 million homes by 2030 and 25 million homes by 2045. But no such projects are in the works yet. Planning them, obtaining an array of permits and construction could take at least seven to eight years.

Build 15 times more public chargers: About 1.2 million chargers will be needed for the 8 million electric cars expected in California by 2030. Currently, about 80,000 public chargers operate statewide, with another estimated 17,000 on the way, according to state data.

Expand vehicle-to-grid technology: State officials hope electric cars will send energy back to the grid when electricity is in high demand, but the technology is new and has not been tested in electric cars.

Increase electricity production by up to 42% in 2035 and, under a recent scenario, as much as 85% in 2045, according to California Energy Commission estimates. Generation capacity — the maximum that must be installed to meet demand throughout a given year — would need to triple by 2045.

Day and night charging

Climate change has already stressed California's energy grid, especially during hot summer months when residents crank up air conditioners in the late afternoon and early evening.

Providing electricity during those hot summer evenings — when people use the most — will be a challenge, said Gee of the California Energy Commission.

"That's what we're particularly concerned about," he said. "We have enough electricity to support consumption the vast majority of the time. It's when we have those peak hours during those tough months."

The total electricity consumed by Californians is expected to surge by 96% between 2020 and 2045, while net demand during peak hours is projected to increase 60%, according to a study commissioned by San Diego Gas & Electric.

Southern California Edison worries that if drivers charge during late summer afternoons, electric vehicles could strain the grid, said Brian Stonerock, the utility's director of business planning and technology. Edison's service area includes the desert, where customers rely on air conditioning, and their peak use times are when solar power is less available as the sun goes down.

Concerns about the grid "are quite a big deal for us," he said. "We don't want people to be confused or lose confidence that the utility is going to be able to meet their needs."

But for many drivers, charging during the day or late at night is not a problem: Most electric cars have chargers that can be automatically turned on after 9 p.m. But for some drivers, especially those who live in apartments or condominiums, charging during those hours may not be an option.

That's because — unlike filling a gas tank — charging an electric car takes much longer. Drivers may not have a reliable place to park their cars for long periods of time during the day while they work or late at night when they're home. To encourage daytime charging, Victor said the state must drastically boost the number of fast chargers and workplace stations.

Fast chargers — like the Tesla superchargers available at some public spots — can juice up a battery to 80% within 20 minutes to an hour. But most chargers are a lot slower: A level one charger, often supplied by manufacturers, could take between 40 to 50 hours to fully charge an empty battery. An upgraded, level two charger can take four to 10 hours, according to the U.S. Department of Transportation.

"A lot of the increase in demand is going to come from electrifying transportation and it's really going to hinge on when people charge. That's a behavioral and technological question that we really don't know the answers to," Victor said.

The California Public Utilities Commission in 2015 ordered state's investor-owned utilities — San Diego Gas & Electric, Southern California Edison and Pacific Gas & Electric — to transition its residential customers to rate plans that offer lower pricing during off-peak hours.

For instance, in the summer when energy is the most expensive, PG&E customers pay about 55 cents per kilowatt-hour during peak hours, more than double the 24 cents during off-peak times, according to PG&E spokesperson Paul Doherty.

These time-of-use rates have been a "highly successful" strategy, Doherty said. Most PG&E customers take advantage of the lower pricing: On average, between 60% to 70% of electric vehicles in PG&E's service area are charged during non-peak hours.

But not all state leaders are convinced that discounts alone will convince electric car owners to lay off charging in evenings.

"Moving forward into the future, it seems to me that the strategy is putting more and more stress and responsibility on the customer," Assemblymember Vince Fong, a Republican from Bakersfield, told state agencies at a joint legislative hearing in November. "You've got an electricity grid that is leaning on customers to do more, instead of, actually, as a state, generating the power we need to keep the lights on."

For PG&E customers, charging an electric vehicle when rates are lowest — between midnight and 3 p.m. — is roughly equivalent to paying about $2 for a gallon of gas, Doherty said. But as rates keep rising, charging a car could cost more than filling a gas tank.

"The cost of electricity is trending so high that it represents a threat to California meeting its goals," said Mark Toney, executive director of the advocacy group Utility Reform Network.

A rush to replace natural gas and nuclear plants

California will soon lose major sources of electricity: the Diablo Canyon nuclear power plant and at least four coastal natural gas plants. Combined, nuclear power and natural gas provide nearly half of the total electricity consumed in California.

To replace them, the state Public Utilities Commission has ordered utilities by 2026 to procure 11.5 gigawatts of new renewable energy resources, or enough to power 2.5 million homes.

A new state mandate requires 60% of California's power supply to come from renewables by 2030 — nearly double the amount of 2022.

And by 2045, solar and wind combined must quadruple, according to the California Energy Commission. That's about 69 gigawatts from large-scale solar farms, up from 12.5 gigawatts, plus triple the amount of rooftop solar and double the amount of onshore wind power.

California's target to build at least 6 gigawatts of solar and wind energy and battery storage a year for the next 25 years is daunting, given that in the past decade, it's built on average just 1 gigawatt of utility solar and 0.3 gigawatt of wind per year. In the past three years, the pace sped up, with more than 4 gigawatts added annually, state data shows.

Solar farms face big obstacles: insufficient materials for energy-storing batteries and a need for more transmission lines, especially in the Central Valley, a prime place for solar, said Shannon Eddy, executive director of the Large-scale Solar Association.

There's also some "not-in-my-backyard" pushback in the desert and other rural communities. San Bernardino County outlawed solar farms on more than a million acres, and two projects were rejected in Lake and Humboldt counties.

To speed clean energy projects, Gov. Gavin Newsom and the Legislature enacted a controversial new law allowing state agencies to usurp control from local governments for siting solar, wind and some battery backup projects.

Alex Breckel of the Clean Air Task Force, an environmental advocacy group, said the state's clean-power goals are achievable. Still, he said, new generation, energy storage, distribution systems and transmission lines will take substantial time to deploy.

The state must ensure that the transition to clean electricity protects the environment, is affordable and equitable, and avoids delays and siting issues, Breckel said. That's why California needs a robust clean energy deployment plan and to assign a lead agency rather than relying on piecemeal strategies, he said.

"Is the state on track to achieve its clean energy goals? Right now, there's no one who can give you a definitive answer. More transparency on a plan that goes from here to there every year where we can track progress will really help answer that question," Breckel said.

Several lawmakers say the state isn't moving fast enough.

Assemblymember Phil Ting, a Democrat from San Mateo County, lambasted state agencies at the November hearing, saying they have no clear way to speed up new clean energy projects.

"What you're saying to me is 'We're working on it, and we have no idea when we will make the system better' and there's nothing that you're telling me that we could do as a state to make improvements," he said. "Your answer is absolutely not appropriate. ... It's very concerning."

Ting expressed frustration that state leaders were "going backwards" by extending the lifespan of Diablo Canyon to 2030 and some fossil fuel plants. Fearing emergency brownouts like those that hit the state in 2020, Newsom and the Legislature last summer allowed some natural gas plants that were supposed to go offline this year to keep operating past 2023, and perhaps much longer.

Assemblymember Luz Rivas, a Democrat from the San Fernando Valley, said low-income communities near the gas plants will continue to suffer the most if the state keeps extending their retirement dates.

"We can't forget about the costs that low-income communities like mine will bear from this," Rivas said. She said "many disadvantaged communities across the state bear the brunt of impacts" of pollution from fossil fuels and climate change's extreme heat.

Siva Gunda, a member of the California Energy Commission, acknowledged that the state "needs to do better to make sure we are on course to retire the fossil-fuel generation and not burdening communities."

Gunda said the commission will have a report for legislators later this year. "You're absolutely right that we need a long-term strategy for making sure we can get through the peaks with clean resources," he told legislators.

Hinging hopes on wind farms

California is betting on giant wind farms in the ocean to strengthen the grid and meet its renewable energy goals.

The state's ambitious offshore wind targets build off President Joe Biden's 2021 pledge to deploy 30 gigawatts of offshore wind nationally by 2030. Newsom hopes to add between 2 to 5 gigawatts of offshore wind off California's coasts by 2030. Ultimately the state aims to produce at least 25 gigawatts from offshore wind by 2045 — the boldest commitment any state has made. That could supply electricity for 25 million homes.

Last Dec. 6 was a historic day: The first-ever auction of wind leases in waters off California was held, with 43 companies leasing 583 square miles in five areas off Morro Bay and Humboldt County. These deep ocean waters have the potential to produce more than 4.5 gigawatts, enough to power about 1.5 million homes.

That sounds promising, but the state is hinging its hopes on an emerging sector that doesn't yet exist in California — and vast regulatory and technological hurdles lie ahead.

California will need expanded ports, and developers must first submit detailed plans about a project's cost and scale before facing extensive environmental reviews.

Adam Stern, executive director of the industry group Offshore Wind California and former executive director of the Palo Alto environmental nonprofit Acterra, said the planning and regulatory process alone could take five to six years. Installing the massive turbines — with blades bigger than a football field — and constructing transmission lines and an onshore production plant would take another two to three years, Stern said.

"It's a huge challenge," Stern said. "It's going to require a lot of coordination and a lot of investment and a lot of collaboration across different types of stakeholders, government industry, non-governmental organizations and labor unions."

Current offshore wind turbines off the East Coast are fixed to the ocean floor in shallow waters. But California's turbines would be the first in the nation to float on platforms anchored by cables in waters reaching about half a mile deep.

This new technology won't be cheap. The cost of producing the energy averages about $84 per megawatt-hour, more than most other sources of energy, according to the U.S. Department of Energy.

Still, offshore wind's potential is huge. Wind power tends to be stronger in the ocean than on land, making it valuable during times when renewables like traditional wind and solar can't produce enough energy. Winds off the coast are also strongest in the late afternoon and evening, which is exactly when — particularly in the summer — electricity demand surges.

Offshore wind farms "offer the promise of a lot of clean energy at the time of day and season when we need it most," Stern said. "Even as hard as this is going to be, I have a lot of optimism that we can pull it off."

A million chargers and vehicle-to-grid technology

As electric cars surge, so will demand for public chargers. California has about 838,000 electric cars and plug-in hybrids. By 2030, about 1.2 million chargers will be needed for 8 million vehicles, according to a state report. Currently, only about 80,000 public chargers have been installed statewide, with another 17,000 on the way, according to state data. The goal is 250,000 by 2025.

Mostly, private companies are responsible for installing them, although state grants help. A standard level 2 charger could cost between $7,000 to $11,000, while direct fast charging costs about $100,000 to $120,000 each, according to the California Energy Commission.

California is deploying new chargers with funds from a $8.9 billion investment for electric vehicle incentives from this year's budget. Those dollars are being used for 170,000 new chargers.

In addition, California also received $384 million in federal funding this past year to help it construct a 6,600-mile statewide charging network and deploy 1.2 million chargers by 2030, according to the California Energy Commission.

"Every major automaker in the world is now making electric vehicles and we need to make it possible to charge everywhere in the state for everyone," said David Hochschild, who chairs the California Energy Commission.

Securing the stability of the grid also requires a huge investment in energy storage, which can help provide energy during peak demand times. One method is called vehicle-to-grid integration, where energy can be reabsorbed by the grid when the vehicle is parked.

So far, the only projects that exist in California are for buses. San Diego Gas & Electric and a battery company deployed a first-of-its kind project with buses that have battery capacity five times greater than an electric car's.

The technology is still in the early stages, has not been tested with other electric vehicles and it's unclear when it will be ready.

Rajit Gadh, director of UCLA's Smart Grid Energy Research Center, said challenges exist.

Some car owners may not want to use the technology because they worry that it could affect their car battery's life. While studies have not reported battery damage, convincing consumers could be a slow, difficult process, he said. Utilities will have to sway them with cheaper rates and other incentives for it to work.

As with many of the problems related to energy and electric vehicles, "It's a matter of time, education, awareness and incentives," Gadh said.