People spend a lot of time on Facebook -- comparing interests, sharing photos, stalking old high school crushes. Now they can also start seeing how their energy use stacks up against their friends' habits.

The Social Energy App, which launched yesterday, is a partnership between Facebook, the Natural Resources Defense Council (which publishes OnEarth), and Opower, a software company that helps customers connect with utilities. With Social Energy, Facebookers can easily track how many kilowatt-hours they consume each month and broadcast their numbers alongside photo albums, status updates, and wall posts. With a mix of peer pressure, competition, and positive reinforcement, Social Energy encourages users to lower their electricity consumption –- and then brag about it.

"People are particularly responsive to the idea of keeping up with the Joneses," says NRDC attorney Brandi Colander, who works on air and energy issues and helped develop the app. Why not harness that competitive instinct for a greener good?

Ten utility companies, which include ConEd and Pacific Gas & Electric, have joined the project already. Their customers, about 4 million Americans, can now pull their utility information directly into their smartphones. And what do we love to do with phones? Communicate with friends.

The app tracks your personal energy stats and shows how your friends are doing. For example, I can poke fun at my dad for how much more electricity it takes to heat my parents’ house in upstate New York. (You may be surrounded by trees, Mom and Dad, but my Brooklyn apartment is definitely greener!) Another feature allows users to team up in groups to tackle bad consumption habits together.

To start, Social Energy directs you to the Opower site, where you'll answer basic questions about your home and location and then upload information from recent electric bills.

Warning: when signing up, the app asks if it can post status updates for you. Only say yes if you’re confident you want to show the world how much you consume. If you opt out, you can change your mind later when you feel ready to share (perhaps after easing up on the A/C for a month).

Importantly, if you aren't sure how to improve your performance, the app won't leave you alone in the dark eating cold Pop-Tarts. Social Energy shares plenty of advice on how to cut consumption, which you can then pass on to your peeps. Some tips are pretty obvious: let clothes and dishes air dry, pick energy-efficient appliances and light bulbs, etc. Others are much less so, but just as simple. For example, I’ve never thought about cleaning my refrigerator coils or using spotlights instead of overhead lighting while working.

“What we’re doing is using a social networking platform that people are already familiar with,” says Colander, explaining why she thinks Social Energy will succeed where other energy consumption apps and websites have failed. And if good old-fashioned competition doesn’t spark peoples' motivation, the new app might also give away prizes to those achieving the biggest dips in energy use. I’ll give a Facebook thumbs up to that.

Image: Opower