Chicago will refinance up to $2.5 billion in debt in a way that could dramatically reduce interest rates and possibly save taxpayers up to $75 million a year, Mayor Rahm Emanuel told investors Wednesday.

Emanuel disclosed he would take advantage of the new financing vehicle authorized by the General Assembly as he put organized labor on notice.

Now that contracts with 90 percent of the city’s work force have expired, Emanuel plans to follow Inspector General Joe Ferguson’s advice to seize a “generational moment” for Chicago to tilt the playing field in favor of taxpayers by cutting costs and improving city services.

“As we negotiate the new contracts, I expect … to see savings in wages and benefits, health care and other places that are key to the city of Chicago’s future,” the mayor told investors.

“You have to be at this table trying to figure out how to get to a ‘yes’ for both sides. … And I expect them to be a partner in trying to find the savings … to help Chicago be in a stronger position from a fiscal standpoint.”

The budget deal that ended the marathon state budget stalemate authorized Chicago to set up what a top mayoral aide called a “special-purpose corporation” as a vehicle to borrow money to finance city projects.

The Emanuel administration intends to put state sales tax receipts into that corporation, then borrow against it at a dramatically reduced interest rate — anywhere from 1.75 percentage points to 3 percentage points lower than Chicago taxpayers pay now.

A 3-percentage-point reduction in borrowing costs would save the city $30 million a year on every $1 billion borrowed.

Chicago has $10 billion in outstanding general obligation debt backed by property taxes. Roughly $2 billion of that borrowed money can be refinanced early, without penalty, in the next two or three years.

In addition, the city is considering refinancing about $515 million worth of sales tax bonds, because “the new financing structure will work best if the city does not have any other bonds pledged to those revenues,” officials said.

A top mayoral aide, who asked to remain anonymous, predicted the savings to taxpayers would be “much more significant” than routine refinancing because bonds issued under the new structure would have a “significantly higher rating.”

That’s because the legislation allows the city to “isolate revenues from the rest of the city’s corporate fund,” and thereby shields investors from the threat of being dragged into a bankruptcy proceeding.

“Bond holders have greater protection that those revenues will first go to them to pay that debt service and then go to the city for general use. Bond holders … and the rating agencies like this structure. That gives it a better rating and a lower interest rate,” the top mayoral aide said.

“It could be as little as 1.75 percent lower than our current interest rate and as much as 3 percent lower. And over time, our [general obligation] rating is expected to improve because we’re not depending on it as much to borrow because we have this other structure.”

Chicago’s junk bond rating has already saddled taxpayers with tens of millions of dollars in penalties and added borrowing costs.

The Emanuel aide said the new financing scheme — already used in New York City, Philadelphia and Washington D.C. — could pave the way for the city to raise a bond rating that now ranges from BBB-plus to junk with Moody’s Investors.

“It’s one additional thing that the mayor is putting in place that should help to improve our overall financial outlook,” the mayoral aide said.

Last week, the Emanuel administration disclosed a $114.2 million budget shortfall in 2018 that does not factor in the steep cost of police reform, the second year of a police hiring surge or pay raises for the 90 percent of city employees whose contracts expired on June 30.

Emanuel’s plan to hire 266 police officers, 100 detectives and 75 sergeants in 2018 carries a $70 million price tag.

Yet another round of tax increases — including a 28 percent increase in the monthly tax tacked onto Chicago telephone bills — is virtually guaranteed. The mayor is also considering raising taxes on downtown businesses, high net-worth individuals or both to put the broke Chicago Public Schools on solid financial footing.

But Emanuel assured investors that he would continue to take a “balanced” approach to new taxes.

“I’m not gonna make up in two or three years what took 30 years to create,” he said.