ObamaCare officially opens for business Tuesday. Unfortunately, it’s already falling short of promise.

The plan:
Tomorrow, Americans are supposed to be able to start purchasing insurance through “exchanges” — government-managed state marketplaces for health insurance.

Individuals lacking access to “affordable” insurance are eligible to buy through the exchange. Those with incomes up to about 400 percent of the poverty level ($94,200 for a family of four) could be eligible for subsidies. At least 7 million Americans are expected to buy insurance through the exchange by Jan. 1.

‘Success’:
The key words on enrollment are “at least.” Given how fast companies are dropping insurance for their workers and pushing them into the exchanges — Home Depot, for one, just announced it’s dropping coverage for 30,000 part-time workers — millions more Americans are likely to be left with no choice for insurance except the exchange.

Higher prices:
Premiums will vary widely depending on where you live. In a few places like New York City, which have long suffered from dysfunctional insurance markets, some people may pay a bit less than before, especially those getting subsidies. But elsewhere — upstate, for example — many will pay considerably more.

Yes, the federal Health and Human Services Department recently said ObamaCare premiums are “lower than expected,” but that “expected” means Congressional Budget Offices projections — which were that insurance costs would rise.

Comparing the data from that HHS release with current premiums, one study found that a young person would face an average increase of roughly 76 percent, while a 40-year-old would see an average increase of 80 percent.

In another study, National Journal — not generally known as part of the vast right-wing conspiracy — found that, even after accounting for subsidies, most Americans will pay more in premiums for ObamaCare plans than they do for their employee plans today.

And out-of-pocket costs — deductibles, copayments, co-insurance — are all likely to be higher for exchange-based plans. A study by Avalere Health found that ObamaCare’s “affordable” bronze plans had an average deductible of $5,150, more than four times higher than the average deductible in employer-sponsored coverage this year.

By one estimate, all the added costs for the average family of four over the next eight years add up to an extra $7,450 due to ObamaCare.

Fewer choices:
Those shopping on the exchange are apt to find relatively few plans to choose from, since several large insurers have declined to participate. In New York, for example, Aetna, the nation’s No. 3 insurer, has withdrawn from the state-run exchange.

And the insurance plan you buy may not include your current doctor. As The New York Times reports, many insurers are trying to control costs by cutting down the number of hospitals and doctors in their networks.

‘Glitches’:
That’s what the Obama administration euphemistically calls some early problems. For example, that the software that determines how much people actually have to pay for the insurance can’t actually calculate the price. Oops.

Invitation to fraud:
The system also can’t verify your income or whether your employer offered you “affordable” coverage. So Team Obama says it will often have to rely on applicants’ “attestation” — that is, take their word for it. After all, who would lie?

Identify theft:
To figure out who’s eligible for subsidies or Medicaid, the exchanges will collect both tax and health-care data from applicants — everything from last year’s income to the prescription drugs you take. All that data’s supposed to go into a “data hub” that draws on records from at least seven different government agencies — the IRS, the Social Security Administration, Homeland Security, the Veterans Health Administration, the Department of Defense, the Office of Personnel Management and the Peace Corps.

But the administration has missed repeated deadlines for testing, reporting and correcting security risks for the hub. The program’s security is supposed to be certified … today — the day before it goes into effect.

That’s not all. State-employed “navigators” are supposed to help people through the exchange’s byzantine application process; they’ll have access to such sensitive information as your Social Security number, date of birth, bank account number, place of employment and medical history. But many states hired navigators without doing criminal background checks; the only definite requirement is 20 hours of training.

For years we’ve been debating ObamaCare. Now, at last, millions of Americans are about to find out exactly what it means for them. They’re not likely to be pleased.