Alan Horn’s plan is to have no plan.

He’s departing Friday after a dozen years as Warner Bros.’ president and chief operating officer. Aside from a consulting gig at the studio through 2013, he’s deliberately put off making a decision on what he’ll do. But he is firm about one thing he won’t do, which is taking a producing deal with WB.

So instead of driving to Burbank on Monday, he’ll head to Century City, where he’s taken an office near his former partner, Jerry Perenchio.

“I’m a very decisive person — I’ve had to be in this job — and I’ve decided that I don’t want to decide until I’m out of this office,” he said Wednesday. “It’s really been an all-encompassing job when you’re releasing 24 movies a year, so I’m looking forward to unplugging. I won’t be reading four screenplays over the weekend and reading a book that we’re trying to turn into a film.”

The 68-year-old Horn — whose studio’s been consistently the top performer during his tenure — has started to fill cardboard boxes with memorabilia.

“I really need to unplug to figure this out,” he added. “For now, I don’t want to be committed to anything.”

Horn has known that his departure was coming since September, when Time Warner topper Jeff Bewkes announced that Horn’s slot would be replaced by a three-person “office of the president” — filled by motion picture group prexy Jeff Robinov, TV group topper Bruce Rosenblum and home entertainment chief Kevin Tsujihara. He hasn’t been shy about letting people know that it wasn’t his decision to exit the studio, which is one reason he isn’t sticking around on the lot.

“I don’t want to do that because it has a ‘been there, done that’ kind of feeling for me,” he added.

However, Horn acknowledged that there’s a possibility he may become involved with Warner Bros. Theater Ventures, which he’s overseen. The unit has produced such plays as “Elf.” He may also become more active in philanthropy — a route taken by former Paramount topper Sherry Lansing after she left her studio five years ago — along with environmental causes and Democratic politics.

Horn sits on the boards of the National Resources Defense Council, the Gene Autry Museum and Harvard Business School but admits that the Warner duties have made it difficult to spend as much time as he would have liked on those panels. He also plans to spend more time at the gym, but he insists that he’s being as vague as possible for now as to any business plan.

“When I decide, it’s going to be on a very ad-hoc basis,” he added. “There’s not going to be a big announcement.”

Horn noted that he’s now had three careers of about a dozen years each — first at Embassy Pictures with Perenchio and Norman Lear before it was acquired by Coca-Cola followed by his time at Castle Rock with Rob Reiner, Glen Padnick, Martin Shafer and Andrew Scheinman. Castle Rock was merged into Warners 15 years ago.

Warner Bros. chairman-CEO Barry Meyer and Horn have headed Warner Bros. since October 1999, when they replaced longtime toppers Bob Daly and Terry Semel. Since then, Warners has been at or near the top of the box office in most years — thanks largely to betting big on tentpoles such as the Harry Potter pics, “The Dark Knight,” “Sherlock Holmes” and “Inception.”

Horn said Wednesday that his biggest accomplishment has been execution of the tentpole strategy on a worldwide basis. He’s overseen all seven Potter films, which have combined for $6 billion in worldwide box office.

Horn stressed that he was particularly impressed that Robinov had the insight to push ahead on “Inception” despite the complexities of the multi-layered storytelling. Horn also insisted that he wants to help Robinov, who will sole greenlight authority over features, in any way possible.

“I took the baton from Bob and Terry 12 years ago and I’ve had to run very fast since then,” he added. “It’s really Jeff’s turn now.”

Horn emphasized that he and other Warner execs have tended to avoid seeking publicity about themselves.

“That reticence isn’t arrogance,” Horn noted. “We always feel that the movies should speak for themselves. What isn’t mentioned enough is the artistry that goes into films and how really hard it is to make them.”

And even after greenlighting several hundred Warner films since 1999, Horn’s also struck with just how imprecise moviemaking is.

“You’re going to fail some of the time,” he admitted. “My takeaway from all this is you have to love movies because you’re immersed in them. I admit that I loved ‘The King’s Speech.’ I called my sister in Buffalo and told her she had to see it even though it wasn’t ours.”