Don’t understand why people pay to join a gym and run on a treadmill when they can run on perfectly nice non-motorized surfaces — a.k.a. roads — for free, emissions-free? Then I’m guessing the idea of a solar-powered stopwatch to keep track of your workouts — and to keep green all the energy expended during your run — may appeal to you. After all, solar watches like outdoor runners too, since they can charge up with the free energy from the sun while you move.

Now, fans of Casio’s Baby-G watches can keep time with the sun. The newish Eco-Baby-G uses what Casio calls “Tough Solar Technology,” by which the watch’s face basically captures some of the sun’s power to charge up its internal battery. This green, solar-charging feature helps reduce battery waste — and avoids the potential metal and chemical pollution from batteries.

Assuming the watch sees the outdoors for a few minutes most days, Eco-Baby-G wearers will be able to tell time — as well as use the countdown timer, alarm clock, and phone number directory — as with conventional Baby-Gs. Eco-Baby-G only needs five minutes of outdoor sunlight a day for normal functions — though of course if you’re fiddling with it a lot, making it light up all the time, you’ll need to let the watch see more light.

Charging up the watch indoors with fluorescent lights takes considerably longer — about 10 times longer than with good old sunlight — so the the Eco-Baby-G’s not a good idea for those who stay cooped up. The watch always displays a H, M, or L sign (high, medium, low) to let you know its energy level. If you leave the watch in the dark too long, the Eco-Baby-G will start using its own power saving controls, disabling some functions to conserve energy, until you let it into the light again.

Unfortunately, it’s unclear how much longer a solar-rechargeable Eco-G-Baby will last you than a conventional battery will. Casio’s manual says the solar battery will eventually die “after very long use” — but requests for more details on how long “very long” were met with silence. Since the watch initially arrives fully charged — which means it’s basically good to go for about a year even without additional solar power — it’ll be a while before any user who buys it now will be able to find out how long “very long” is.

Eco Baby G

Decide for yourself if you’re willing to take that gamble. The Eco-Baby-G comes in easily recyclable, recycled paper packaging, with just one small bag of plastic protecting the watch’s face. Find it at Macy’s or buy it online at the Baby-G website for $110.

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