More than two years ago, lawmakers approved billions of dollars to build out a national electric vehicle charging network in the hopes of encouraging more drivers to switch to cleaner cars. The money, included in the bipartisan infrastructure law, was intended to help assure drivers they could reliably travel longer distances without running out of power.

But a robust federal charging network is still years away. Only two states — Ohio and New York — have opened any charging stations so far. A handful of others have broken ground on projects in recent weeks, with the aim of completing them in early 2024. In total, 28 states, plus Puerto Rico, have either awarded contracts to build chargers or started accepting bids for projects as of Dec. 15. The rest are much further behind on starting construction.

Broad availability of chargers is critical for the Biden administration’s goal of getting electric vehicles to make up half of new car sales by 2030. Americans routinely cite “range anxiety” as one of the biggest impediments to buying an E.V. About 80 percent of respondents cited concerns about a lack of charging stations as a reason not to purchase an electric vehicle, according to an April survey from the Energy Policy Institute at the University of Chicago and the Associated Press-NORC Center for Public Affairs Research.

The Biden administration is trying to entice consumers to buy electric vehicles both by offering tax credits of up to $7,500 and promising to build out a national backbone of high-speed chargers. That network is meant to give drivers the assurance that they could reach a reliable charger every 50 miles along major roads and highways.

The White House has set a goal of building a national network of at least 500,000 public chargers by 2030, but researchers at the National Renewable Energy Laboratory have projected that the country will need more than one million public charging ports by the end of the decade.

Ben Shapiro, a researcher at RMI, a nonprofit that promotes the energy transition, said the country needed to accelerate the pace of new charging infrastructure considerably.

“People certainly have this perspective that there isn’t enough charging,” Mr. Shapiro said. “And that I think does hamper people’s interest in E.V.s.”

Electric vehicle sales have been climbing faster than any other major category of automobile, with the nation on track to hit more than one million sales for the first time this year. President Biden’s signature climate law, the Inflation Reduction Act, has also spurred a surge of investment in electric vehicle production across the country. But demand has not grown as much as expected.

Some state transportation officials said the rollout has taken more than two years because they had little experience building chargers and it has been challenging to navigate new federal requirements.

In Tennessee, officials started reviewing bids for contracts after closing applications last month. Preston Elliott, a deputy commissioner of the state’s transportation department, said he thought Tennessee was moving quickly, but it still took officials about two years to get to that stage, in part because they had to submit two plans to the federal government and wanted to have conversations with stakeholders before opening bids.

“Federal funds come with lots of requirements and lots of strings,” Mr. Elliott said. “I’ve been doing this for about 30 years, and this is the first time I’ve ever encountered a program where you’ve had to do so much planning before you spend a penny.”

The U.S. Transportation Department issued final rules for the program early this year, outlining technological requirements and standards that have to be met. Chargers must be within a mile of an interstate exit or highway and have four ports that are all operational and meet minimum power levels 97 percent of the time.

But the law gave states flexibility to determine how to award contracts and dole out funds, resulting in varying degrees of progress.

Ohio became the first state to open a charger funded by the new program earlier this month. Mike DeWine, the state’s Republican governor, cited charging concerns as a primary reason for getting the system up and running. There are about 43,200 electric vehicles registered in Ohio.

“This industry is not going to develop unless people think they have places where they can charge their car,” Mr. DeWine said. “We want to send the signal that not only are we getting companies in here that are building things for the future, but we want our consumers in Ohio to have the ability to benefit from that.”

Six more charging stations are being designed and expected to begin construction in the next month or two, state officials said. Officials expect to build about 50 charging stations by the end of 2026 to meet the program’s requirement.

Most states are well behind Ohio and New York. While some are bidding out contracts to build the network, the actual installation of all of the chargers can take years to finish because projects have to clear environmental reviews and other bureaucratic hurdles in addition to the construction, state officials said. Some states are also building chargers in several phases.

“If you were talking about building a sidewalk, we build sidewalks all day long,” said Mr. Elliott of Tennessee. “When you start talking about a charging system, being open 24/7 and meeting certain power thresholds, I mean, think about the complexities of that.”

Mr. Elliott said state officials were planning to fund 32 charging stations to meet the program’s requirement and aimed to complete those projects in two years once contracts were awarded.

Some states with sparse populations and little charging infrastructure have also taken longer to roll out their programs. In Wyoming, the state’s transportation department began accepting responses this month from potential station owners to better gauge interest in using the federal funds, which can cover up to 80 percent of the project’s cost, plus operating expenses.

State officials said they did not know when or if they would award contracts because that would depend on the level of interest. Keith Fulton, an assistant chief engineer at Wyoming’s Transportation Department, said the process was taking more than two years partly because the department has never installed an electric vehicle charger before.

States are also considering the types of connectors they will need. Although they only have to provide ports with Combined Charging System connectors, some states, such as Texas, will also require the plugs that Tesla cars use, known as the North American Charging Standard. Ford and General Motors have also announced that they would equip future vehicles with Tesla’s ports.

Loren McDonald, the chief executive of EVAdoption, a data and analysis firm that has been tracking each state’s progress, said it was concerning that some automakers have not been clear about whether they will provide adapters with the purchase of vehicles. That is in part because it could complicate the ability of some drivers to use the new chargers. But he noted that Tesla has won many of the bids so far, and other station owners will probably make upgrades to adapt to the market.

Senior Biden administration officials said they expected to see a wave of new chargers becoming available in the coming months, and the federal government had taken steps to help states move more quickly, including streamlining environmental permitting processes. Once states completed the planning and design work, they would be in a position to move much faster, they said.

Gabe Klein, the executive director of the federal Joint Office of Energy and Transportation, pointed to new private investments in charging infrastructure and said he expected the country to reach the administration’s goal before 2030.

“The private sector investment is staggering,” Mr. Klein said.

Nick Nigro, the founder of Atlas Public Policy, a policy and data research firm, said states have made substantial progress, but much of the work has not been visible to the public.

“I can imagine from the outside that it might look like this is taking a while,” Mr. Nigro said. “But that is the process we’ve set up in this country for how we spend money. There are a lot of checks and balances.”

Although some drivers said they wanted to see state officials use federal funds to build more chargers, they were still hesitant to make the switch to electric vehicles.

Barbara Ziegler, 66, a psychologist in Sheridan, Wyo., said she welcomed more chargers, but she did not feel comfortable yet buying an electric car. She said she often drives more than a hundred miles to see a diabetes specialist, attend conferences and go shopping in larger cities, and she was concerned about being stranded on the road because of the lack of chargers.

Ms. Ziegler said she would consider buying a hybrid car, but for now, she planned to stick with her 2012 Toyota RAV4 until it needed to be replaced.

“Here we have long, long highways without towns in between,” Ms. Ziegler said. “I would be too worried to try and do the drive just on electric.”