What if saving the planet meant giving up Starbucks?

Oh sure, for some people it wouldn’t matter, but for those who wake up thinking about caffeine, it’s a serious question – one that the latte-loving Michelle Conlin has to answer as her husband drags her into the adventure that is “No Impact Man.”

Directed by Laura Gabbert and Justin Schein, this funky family story follows Colin Beavan, whose mission is to spend one year at his apartment in Manhattan leaving as little a carbon footprint as possible (and to write a book about it, which makes the undertaking less than totally altruistic, but what the heck).

As he must, he takes his small family into the green zone with him, including the slightly less-than-enthusiastic Conlin, who isn’t at all sure about going down the crunchy road of no electricity, no refrigeration, no mass transit – and earthworms breaking down compost in the living room.

“Daddy does nature,” she tells daughter Isabella. “Mommy does retail.”

But Conlin comes around. And given that she’s the stand-in for all the armchair environmentalists in the audience, that’s not a discouraging thing.

Successful evangelists of every stripe know the best way to sell: Put a human spin on the pitch.

Had “No Impact Man” been pure propaganda – as opposed to adulterated propaganda – it would have been easier to dismiss as a stunt or as some preachy extremist sermon.

As it is, it’s more of a how-to: how to reduce that carbon footprint, of course, but also how to strip one’s life of unnecessary baggage.

Beavan and “No Impact Man” won’t be getting much love from Starbucks, but thanks largely to Conlin and her convert’s perspective, it’ll earn more than a bit from its audience.