In 2009, 17.2 million Americans worked remotely at least one day per month, an increase of 39 percent over the previous two years. (Doug Griswold/San Jose Mercury News/MCT)

Not long ago, I interviewed the chief operating officer of electrical giant Exelon in my jammies.

He didn't seem to notice.

I was telecommuting from my dining room, doing my part for the planet.

Increasingly, other Americans are, too.

In 2009, WorldatWork, a human resources association, found that 17.2 million Americans worked remotely at least one day per month, an increase of 39 percent over the previous two years.

It's convenient, for sure. On days when traffic congestion is an issue -- snowy days come to mind, when an hour's commute can stretch to two -- it's a time-saver. And, I contend, a sanity-saver.

Bosses' fears about production have not been realized. According to a Cisco Systems study of its own employees, the networking company increased productivity by $277 million in a year.

Most employees divvied up their former commute time this way: They worked 60 percent of the time they saved, and turned 40 percent of it into personal time.

The question: Is this a greener way to go?

The surprising answer: Not always.

If you take public transportation, working from home doesn't really get you anywhere. The train or bus would have run anyway.

Working in an office has obvious efficiencies. Unless you're Mr. or Ms. Big, the typical office has a lot of people in small spaces, sharing light and heat. Without you, your mates at the office will still have these cranking. You'll just turn on extra at home.

But in most cases: You bet.

Especially if you would otherwise drive 40 miles each way in an SUV. According to the U.S. Census, 76 percent of workers get to work driving alone.

Especially if you do this in a region with significant air pollution problems related to vehicle exhaust -- like Philadelphia. Every car off the road is pollution avoided.

Especially if your commute lands you on the highways during rush hour. I think of this every time traffic stops on the Schuylkill Expressway. The idling vehicles are still emitting pollutants, but no one's getting anywhere.

Using fuel consumption as a proxy for air pollution, we can turn to the Texas Transportation Institute's annual urban mobility report, released last month. It showed that in 2009, congestion caused commuters in the Philadelphia region to use 106 million more gallons of fuel.

In December, President Obama signed the Telework Enhancement Act, aimed at allowing, or persuading, more federal workers to work remotely.

By one estimate, if federal workers able to work from home one day a week did so, 114 million gallons of gas could be saved.