On her freshman CW series “Ringer,” Sarah Michelle Gellar co-stars in two of them, both identical twins and both in serious trouble.

But that isn’t all for Gellar, who also plays a leading off-camera role as an executive producer.

Even so, the demands on her weigh lighter these days than during “Buffy the Vampire Slayer,” where she labored for seven seasons.

“I work shorter hours on this show – everybody does – than I did on ‘Buffy,’ ” she says with satisfaction. Efficiency reigns on “Ringer.” Her actors and crew members are fellow pros who help get the job done smoothly. She’s having fun.

Meanwhile, she’s keeping work in healthy balance with her private life, enjoyed with her husband of 10 years, actor Freddie Prinze Jr., and their 2 1/2 -year-old daughter, Charlotte, as they give their roles as parents top priority.

“When Charlotte was born, Freddie was on ‘24’ and I didn’t work for two years,” says Gellar. “I had asked him, ‘When I’m ready to go back to work, will you stay home with her then?’ He was like, ‘Fine!’ ” She laughs. “He loves it. I think I’ve created a monster!”

That’s not to say her “Ringer” routine, however moderated, isn’t hectic. Interviewed one recent morning at her Manhattan hotel during a whirlwind publicity visit, she presents herself in sweatpants, a “Ringer” hoodie she grabbed from her L.A. makeup trailer “as I was walking out the door,” and sandals borrowed from the hotel spa. She explains that, in her haste to leave for New York, she neglected to pack clothes or shoes other than the ensembles chosen for her TV appearances.

On “Ringer” (which airs at 9 tonight), Gellar plays Bridget Kelly, an ex-stripper on the run after witnessing a mob hit, as well as playing her troubled New York socialite twin sister, Siobhan Martin, whose own brewing problems compel her to fake her own death. With Siobhan’s apparent death, Bridget sees no choice but to claim her ritzy life and handsome husband in an effort to hide in plain sight from mobsters and the law.

Portraying two characters (plus Bridget masquerading as Siobhan) isn’t so hard, according to Gellar.

“It’s a group effort – hair, makeup, wardrobe,” she says. “Besides, as identical twins, Bridget and Siobhan have characteristics that are inherently very similar. So you don’t have to worry – they have to be able to be confused for each other.”

Her biggest challenge: “keeping in mind who knows what and who doesn’t.”

As an executive producer, Gellar knows everything (far more than her fellow cast members, who, operating on a need-to-know basis, include Kristoffer Polaha, Ioan Gruffudd and Nestor Carbonell). She notes that the seemingly convoluted storyline has been charted out for three full seasons.

“I realize viewers have gotten really frustrated with shows that set up a lot of questions but never answered them,” says Gellar.

On “Ringer,” revelations come weekly, with a major reveal scheduled for the March 13 episode: Viewers will find out why Siobhan went on the lam.

“We would never set up a question if we didn’t know the answer,” Gellar vows.