President Biden’s signature climate law has stimulated a surge of investment in electric vehicle production across the country, including tens of billions of dollars on battery plants across the South and new assembly lines near the Great Lakes. Based on early evidence, it is succeeding at a goal that economists have long considered difficult and costly: using the power of government to rapidly grow a new industry.

That growth could prove crucial for the other side of the electric vehicle equation: enticing more consumers to buy them. That’s because Mr. Biden’s law effectively hitches the future affordability of electric vehicles to automakers’ willingness to source and build them in the United States.

For now, the climate law has not drastically affected trends in electric vehicle sales. Americans are poised to buy one million electric cars and trucks for the first time this year, continuing a steady trend of increased market share for electric vehicles that began years ago.

The law’s most pronounced immediate effect on the consumer market appears to be unintended: driving many electric car shoppers to lease vehicles instead of buying them. That’s because a Treasury Department regulation enables auto dealers to avoid the law’s made-in-America requirements for cars that they buy and then lease to customers. That allows shoppers to effectively reap the full benefits of the federal tax break for models that otherwise would not qualify.

Still, analysts say, electric vehicle sales are projected to jump sharply under the right conditions. Automakers would need to continue to invest in battery and assembly plants. Administration officials must speed the deployment of charging stations meant to ease the logistics of owning and driving an electric vehicle.

Mr. Biden is trying to jump-start the electric vehicle market as the global transition to cleaner fuels is accelerating more quickly than expected. That includes the switch to electric vehicles, which are a cornerstone of efforts to reduce emissions in the sector of the U.S. economy that emits the most greenhouse gases: transportation. Government policy missteps could slow or stall that growth.

The administration’s policies to boost electric vehicles aren’t just aimed at climate change. They also seek to support middle-class jobs for Americans in the auto industry. In a best-case scenario for the administration, those goals work together. The more automakers do to meet the made-in-America requirements in the climate law, the faster the electric vehicle industry will grow to dominate the U.S. auto market.

That relationship is primarily a function of cost. Without an American supply chain, electric vehicles can’t qualify for the full $7,500 consumer tax credit the law created. Without the full credit, a typical electric vehicle remains less affordable than a conventional automobile. Those requirements don’t apply to the leasing market, which explains the shift in consumer preferences.

“I think it’s going to be a long time before you see your local waitress come in and buy an E.V. — they’re just too expensive,” said Rhett Ricart, the chief executive and owner of the Ricart Automotive Group in Columbus, Ohio, and a former president of the National Automobile Dealers Association.

“If we’re going to get people to buy these electric vehicles in volume,” he said, “we will need more financial assistance from the manufacturers or the government.”

The climate law spurred investment at a pivotal moment for American automakers. After a prolonged strike, union autoworkers won new concessions for workers who assemble electric vehicles and produce batteries at some plants that the three largest American carmakers run.

Republican leaders and some Wall Street analysts are calling on carmakers to abandon their plans and refocus on gas-guzzling sport utility vehicles. They claim the vehicle transition is effectively subsidizing China, which leads the world in electric-car technology and is home to vast stockpiles of critical minerals needed for batteries and other components.

The climate law’s champions pitched it as a way to counter China and pull mining and manufacturing to the United States. That group included Senator Joe Manchin III, the West Virginia Democrat who cast the decisive vote for the bill and wielded outsize influence on its every detail.

Under the law, companies get lucrative tax credits for investing in electric vehicle production and component parts like advanced batteries. Consumers get up to $7,500 for buying an electric vehicle. But at Mr. Manchin’s insistence, vehicles qualify for the credit only if they meet certain standards for how much of their content is made and mined in America, or in certain allied countries. Those standards get stricter every year.

Lobbyists from American auto companies warned that those requirements were so stringent that most electric vehicles — other than Teslas — would not qualify. Even Tesla vehicles could soon be excluded.

To avoid losing out, automakers have announced new battery projects across the country, particularly near Detroit and through the Southeast. They include plans from foreign automakers like Hyundai that were immediately excluded from the credit but want buyers to have access to it in the future.

“The response has happened faster than I think anyone would have anticipated on the supply side in anticipation of demand increasing,” Wally Adeyemo, the deputy Treasury secretary, said in an interview. “I think the reason you’re seeing these investments is that, ultimately, these companies see that over time, these credits are going to be quite effective in getting consumers to make a decision.”

One area where companies have been slower to invest in the United States is in the raw materials and parts needed for batteries, including mines producing minerals like cobalt, and factories making chemicals that go into batteries. In the coming weeks, the Biden administration is expected to issue more rules about when these parts can be sourced from China and other countries, which are likely to determine where many companies base new projects.

Another proposed Biden regulation, from the Environmental Protection Agency, is encouraging automakers’ investment in electric vehicle production. It seeks to ensure that two-thirds of all new passenger cars sold in the United States will be all-electric within a decade.

There is little evidence that the climate law has supercharged consumer demand for electric vehicles. American consumers bought about 873,000 electric vehicles in the first nine months of the year, according to Kelley Blue Book estimates. That put the country on a pace to surpass one million electric vehicle sales this year for the first time, but electric vehicles still account for not even one in 10 new cars and trucks sold in the United States.

The pace of that E.V. sales growth is actually slowing: Through the first nine months of 2022, Kelley Blue Book estimated, sales were up nearly 70 percent from the same period in 2021.

The climate law “certainly helped” with electric vehicle sales, said Mike Stanton, the president of the National Automobile Dealers Association. But, he said, “we were hoping for more.”

The law has had a mixed effect for consumers and automakers. The federal government previously offered credits to electric car buyers but capped the total that individual automakers could qualify for. Both Tesla and General Motors, the nation’s largest sellers of electric vehicles, exceeded that cap, meaning some consumers could not claim a credit for buying their cars.

The climate law restored credits for several of both companies’ electric vehicles. It also eliminated credits for many of their competitors, like Hyundai and Kia, that assemble electric cars abroad. As of April, the number of vehicle models that qualify for the full credit had fallen by half compared with how many qualified before the climate law passed. G.M. and Tesla vehicles account for a majority of models that are still eligible for the full credit.

Elaine Buckberg, a former G.M. chief economist who is now a senior fellow at the Salata Institute for Climate and Sustainability at Harvard, wrote in a research brief published in August that years of technological improvements and a consumer aversion to gasoline price spikes had helped electric vehicle sales grow even before the climate law passed.

After Mr. Biden signed the law, she wrote, “sales continued to trend up, with no abrupt shift.”

Ms. Buckberg and other researchers, like Chad Bown of the Peterson Institute for International Economics, have noted one big way the law has changed the electric-vehicle market: It has pushed consumers toward leasing, not buying. That’s because the Treasury Department allowed leased vehicles to be treated differently under the law’s domestic content requirements. Companies like Hyundai and Kia are able to capture the full $7,500 credit for their electric models — and pass that on to consumers — if they lease them.

The auto dealers association calculates that more than half of electric vehicle transactions in the United States — excluding Teslas, which are not sold through traditional dealership models — are leased, a large jump from a year ago.

“For a dealer, that’s easier for me,” said Mr. Ricart, whose holdings in Columbus include a Hyundai dealership.

It is unclear how much the tax credit changes have otherwise influenced consumers’ electric vehicle choices. Tesla’s sales have grown by a quarter this year — but on top of the tax credit re-qualification, it also slashed prices.

Auto dealers and administration officials are hopeful that a feature of the law that will take effect on Jan. 1 will further increase sales. It will allow qualified buyers to immediately pass their electric vehicle credit on to a dealer, essentially using it as a down payment, instead of waiting until they file a tax return to receive money back.

Two years after Congress passed a law that included $5 billion to install fast chargers at 50-mile intervals along major highways, only a handful of states have awarded contracts to construct stations. Chargers remain relatively scarce on most highways.

Spotty availability of fast chargers is shaping up as one of the main reasons that people hesitate to buy electric vehicles. Most owners charge at home. But on longer voyages, they need chargers capable of charging a car in half an hour to 45 minutes.

Kara Womack, an Atlanta resident, owns a Hyundai electric car but is thinking of trading it in for a hybrid because it’s too difficult to drive to visit family in Nashville.

“I don’t know if I’m going to be able to find enough chargers to make it,” said Ms. Womack, vice president of product at ParkMobile, which advises parking lot operators on where to place chargers. “If you’ve got an E.V. and you can’t take it on a road trip because you can’t count on the infrastructure, then it’s a challenge.”

Last month, modeling that the nonpartisan Congressional Budget Office released predicted that the combination of vehicles qualifying for the consumer tax credits and the eventual build-out of the charging network under the infrastructure law would help electric vehicles make up 42 percent of all vehicles sold in America in less than a decade. That would be more than quadruple today’s market share for plug-ins, and significantly higher than the result if Mr. Biden had done nothing to bolster the industry, according to the agency’s study.

Billions of private investment dollars could help speed up expanding the charging network. Operators of roadside travel service centers, like Circle K, Pilot Flying J and Sheetz, are installing chargers alongside gas pumps. Carmakers, including G.M. and Mercedes-Benz, are building charging stations. Next year, much of Tesla’s charging network — the largest in the United States — will open to other vehicles as part of an agreement with Ford, G.M. and other carmakers.

“The states are now rolling and making a lot of progress,” said Andrew Dick, business development manager for Electrify America, a charging company. He added, “Things are starting to move very quickly.”