A $3 million plan to blanket Lompoc, Calif., with a wireless Internet system promised a quantum leap for economic development: The remote community, hit hard by cutbacks at nearby Vandenberg Air Force Base, would join the 21st century with cheap and plentiful high-speed access.

Instead, nearly a year after its launch, Lompoc Net is limping along. The central California city of 42,000, surrounded by rolling hills, wineries and flower fields more than 17 miles from the nearest major highway, has only a few hundred subscribers.

That's far fewer than the 4,000 needed to start repaying loans from the city's utility coffers, potentially leaving smaller reserves to guard against electric rate increases.

And Lompoc isn't alone. Across the United States, many cities are finding their Wi-Fi projects costing more and drawing less interest than expected, leading to worries that a number will fail, resulting in millions of dollars in wasted tax dollars or grants when there had been roads to build and crime to fight.

More than $230 million was spent by U.S. cities last year, and the industry Web site MuniWireless projects $460 million will be spent in 2007.

Without revenues they had counted on to offset that spending, elected officials may have to break promises or find money in already-tight budgets to subsidize the systems for the low-income families and city workers who depend on the access. Cities might end up running the systems if companies abandon networks they have built.

The worries come as big cities such as Philadelphia and Portland, Ore., complete pilot programs and expand their much-hyped networks.

"They are the monorails of this decade: the wrong technology, totally overpromised and completely undelivered," said Anthony Townsend, research director at the Institute for the Future, a think tank.

Municipal Wi-Fi projects use the same technology behind wireless access in coffee shops, airports and home networks. Hundreds or thousands of antennas are installed atop street lamps and other fixtures. Laptops and other devices have Wi-Fi cards that relay data to the Internet through those antennas, using open, unregulated broadcast frequencies. In theory, one could check e-mail and surf the Web from anywhere.

About 175 U.S. cities or regions have citywide or partial systems, and a similar number plan them, according to Esme Vos, founder of MuniWireless.

Rhode Island has proposed a statewide network, while one in California would span dozens of Silicon Valley municipalities. San Francisco, Los Angeles, Chicago and Atlanta also want one.

Because systems are just coming online, it's premature to say how many or which ones will fail under current operating plans, but the early signs are troubling.

"I will be surprised if the majority of these are successful and they do not prove to be drains on taxpayers' money," said Michael Balhoff, former telecom equity analyst with Legg Mason Inc. "The government is getting into hotly contested services."

Most communities, including Lompoc, paid for their projects. Elsewhere, private companies agreed to absorb costs for the chance to sell services or ads.

The vendors remain confident despite technical and other problems. Chuck Haas, MetroFi Inc.'s chief executive, said Wi-Fi networks are far cheaper to build than cable and DSL, which is broadband over phone lines.

Demand could grow once more cell phones can make Wi-Fi calls and as city workers improve productivity by reading electric meters remotely, for instance.

Balhoff, however, says the successful projects are most likely to be in remote places that traditional service providers skip — and fewer such areas exist. Cities, he said, should focus on incentives to draw providers.

In Lompoc's case, officials say construction was delayed about a year once they realized wireless antennas had to be packed more closely together. Then the city learned that its stucco homes have wire mesh in walls that blocks signals, making Internet service poor or nonexistent indoors without extra equipment.

But more importantly, just as Lompoc committed to the network, cable and telephone companies arrived with better equipment and service, undercutting the city's offerings.

"It seemed like we announced we were going to do this and that, and the next day we got trucks from the providers doing this and that, when we've been asking for years and nothing ever happened," Lompoc Mayor Dick DeWees said.

D.A. Taylor, who runs a software business from her home, said Lompoc's Wi-Fi service lacks key features she gets through DSL.

"It's a really great idea, but they didn't spend a lot of time thinking who their target market was," Taylor said.

DeWees acknowledged that Lompoc may have to pull the plug if it cannot boost subscriptions, but he said the city still has an aggressive marketing push in store. Lompoc recently slashed prices by $9, to $16 a month, for its main household plan.

Just a few years ago, these municipal wireless projects seemed foolproof. Politicians got to tout Internet access for city workers and poorer households — many programs include giveaways for poor families. Some cities bear no upfront costs when a company pays for construction in exchange for rights to use fixtures such as lamp poles.

Vendors like EarthLink Inc. saw a chance to offset declines in dialup subscriptions. MetroFi, offering free service, got to join the burgeoning market for online advertising. Google Inc. also is jumping in for the ads, partnering with EarthLink in San Francisco, although the city's Board of Supervisors is resisting their joint proposal.

As projects get started, both sides find unexpected problems.

Many cities and vendors underestimated the number of antennas needed. MobilePro Corp.'s Kite Networks wound up tripling the access points in Tempe, Ariz., adding roughly $1 million, more than doubling the costs.

"The industry is really in its infancy, and what works on paper doesn't work that same way once you get into the real world," said Jerry Sullivan, Kite CEO.