Seventeen months after the U.S. stimulus law authorized billions to subsidize electronic health records (EHRs), 864 pages of rules for how physicians and hospitals must show “meaningful use” of the technology are finally set. Now comes the hard part: implementing the technology in a country where, by one estimate, only 17 percent of doctors use EHRs at all.

“This is a turning point for electronic health records in America, and for improved quality and effectiveness in health care,” David Blumenthal, the national coördinator for health information technology, said in a statement after the rules came out last week.

Ideally, EHRs can warn doctors against prescribing a drug that would interact badly with something a patient is already taking. Or the technology could reveal that a patient has already had a diagnostic x-ray and doesn’t need another one, saving money and reducing radiation exposure. In 2006, the U.S. National Academy of Sciences’ Institute of Medicine said medication errors injure 1.5 million Americans each year–and that computer systems could prevent many of these mistakes.

Such technology can also make it far easier to systematically keep track of patients with chronic conditions. For example, it could identify diabetics who have missed lab tests and appointments and may be at risk of dangerous complications that could include foot amputations.

The money, totaling as much as $27 billion over the next decade, will finally start flowing next May. Individual physicians can receive up to $63,750 if they accept Medicaid, or up to $44,000 if they accept Medicare but not Medicaid. Hospitals might receive millions of dollars.

But to collect the cash–and avoid financial penalties a few years from now–physicians and hospitals will have to show that their systems are not only installed, but are compliant with the new “meaningful use” rules. Among the requirements: that doctors write electronic prescriptions–replacing error-prone handwritten versions–and can give copies of electronic records to patients.

The draft rules came out in January, but were later eased. Under the loosened rules, doctors now must handle at least 40 percent of prescriptions electronically, down from 75 percent. And they must be able to record demographic information on patients in a format that computers can read at least 50 percent of the time. The original requirement was at least 80 percent. Subsequent rules will get more stringent once doctors have begun implementing electronic records.

Given the primitive state of health IT in America, “it’s going to be very difficult for physician organizations” to make the changeover, says Ben Quirk, a partner at TempDev, a health-care IT consulting firm in San Francisco. With that said, “this is a really good opportunity to make the leap,” he adds, and for those who already have some computers installed, “this is a good opportunity to get the real benefits out of their existing system.” Major players, such as GE Health Care, are now customizing their products to comply with the new regulations and will reap a bonanza from the wholesale adoption of information technology.

Despite a longer-than-expected rule-making process at the U.S. Department of Health and Human Services, “it’s going well,” says John Halamka, chief information officer of Beth Israel Deaconess Medical Center and Harvard Medical School, who chairs a key health IT standards panel. “Cost savings from coordination of care and reduction in errors will begin in 2011.”

The benefits will accelerate in 2013, Halamka adds, when more data exchange among organizations will be required. It is this exchange of data–rather than its mere collection–that should eventually reduce redundant care, such as duplicate procedures or prescriptions.

But it remains to be seen how the effort will fare. Meg Aranow, the chief information officer at Boston Medical Center, points out that despite these incentives, hospitals are still facing financial strains brought on by the shaky economy. “Money is being redistributed and reduced in the health-care market,” she says. “So the challenges are considerable, particularly for hospitals and physicians that did not get a head start on this work during better financial times.”

Boston Medical has been an early adopter. It has made electronic connections with several urban community health centers, whose patients often visit Boston Medical to see specialists or receive emergency care. Those connections, only installed in the past year or two, now mean Boston Medical’s doctors can see the electronic records of such patients. But though the connections have provided anecdotal benefits, it’s still hard to prove that patients were better cared for, for less money.