This isn’t just “spare change.”

The city’s homelessness crisis is so out of control that Upper West Side residents are shelling out $120 a month each for private security guards to patrol their neighborhood seven days a week, The Post has learned.

A dozen apartment buildings are part of the desperation effort that’s costing a total $140,000 a year, and they all surround the former Hotel Alexander that the de Blasio administration recently turned into a homeless shelter.

“It’s a classic case of adding insult to injury,” said a resident of 251 W. 95th St.

“The city dumped the problem in our lap, then refused to provide the tools to keep the problem at bay. So now we’re footing the bill ourselves, so at least we don’t have to worry about getting mugged. It’s a total outrage.”

The money pays for a single guard at a time from Cambridge Security Services to keep tabs on the four-square-block area bounded by West 95th Street, Broadway, West 93rd Street and Riverside Drive between 5 p.m. and 1 a.m., except for Fridays and Saturdays, when the hours are 6 p.m. to 2 a.m.

“My initial reaction was ‘I don’t want to do that,’ but people in this neighborhood are upset,” said veteran Broadway and TV actor Bill Tatum, who’s president of the co-op board at The Fremont, two doors from the new shelter at 306 W. 94th St.

“I wish that the police force made the security guard unnecessary. The 24th Precinct is great, but my understanding is they’re stretched a little thin.”

Aaron Biller, a former trade magazine publisher who lives in The Fremont, spearheaded the extra-security plan last year and said it mirrored a similar effort during the 1990s.

Under then-Mayor Rudolph Giuliani, Biller said, “there was a feeling things were getting better.” But he accused Mayor Bill de Blasio of warehousing mentally ill homeless people in the troubled “Freedom House” at 316 W. 95th St. until the city closed it on Dec. 31.

“We’re having to reach into our own pockets and pick up where the government has failed us,” said Biller, president of the “Neighborhood in the 90s” group that is lead plaintiff in a suit seeking to close the new shelter, inside an SRO that still has rent-paying tenants.

Robert Enrick, 38, is one of two security guards that patrol the area. He routinely confronts loiterers to ask them to “go somewhere else” and calls 911 when he gets noise complaints he can’t resolve, encounters emotionally disturbed people or sees flagrant drug sales.

“All the drug dealers go from one shelter to another,” he said.

A doorman at 222 Riverside Drive, Mario Govin, said his building has Enrick and the neighborhood’ s other guard “on speed dial.”

“We don’t have the police on speed dial — they come when they feel like it,” he groused.

One of the tenants he serves, Regan Healey, 55, lamented the extra expense but noted, “We’re all really upset about the number of shelters. When my daughters come back to visit from college, I say, ‘You can’t walk alone.’”

Renee Altholz, of 711 West End Ave., said the guards were an “unfortunate” but necessary solution. “When you see drug dealing and you call 911, they interrogate you as much as they would the perpetrator — ‘What did you see? What kind of drugs were they dealing?’” she said.

“How the hell would I know what drugs? After a while, we gave up calling 911 and put together a few coins to get our own security.”

Altholz, who’s in her 70s, said she often sees one of the guards when she walks her dog at night. “They do make us feel safer,” she said. “They’re friendly, they know us. They’re on the move.”

Neither City Hall nor the NYPD would address the residents’ need to hire guards.

City Hall spokesman Eric Phillips said, “In the safest big city in America, the NYPD will continue to reduce crime to record levels and we will continue to help homeless New Yorkers find shelter.

“Those concepts and missions don’t compete with each other. We’ll do both.”

Police spokesman Phil Walzak said, “The NYPD has added 36 cops to the 24th Precinct over last year and a half, and overall crime there was down 1.6 percent in 2018 compared to 2017.”

“The hard-working, dedicated officers of the 24th Precinct are out there every single day fighting crime, keeping people safe, and improving quality of life,” he added.

A spokeswoman also said city Councilwoman Helen Rosenthal (D-Manhattan), whose district covers the area, was hopeful the closing of Freedom House — and “better security and increased services” at the new shelter — would eliminate the need for the guards.

Additional reporting by Tina Moore and Rich Calder