Electricity is invisible. That’s why we waste so much of it in the home — leaving rechargers permanently plugged in and electronic devices idling in power-slurping “sleep” modes. We can’t see that our houses account for nearly a quarter of the nation’s energy appetite; we don’t know when the grid is nearing capacity and expensive to use.

So Martinez hacked his customers’ perceptual apparatuses. He made energy visible.

That’s the power of “ambient information,” which tries to combat data overload by moving information off computer screens and into the world around us. The Orb was originally sold as a tool for monitoring financial portfolios. You could set it to shine a serene sky blue when your stocks were going up or pulse an alarming red when they were tanking. Studies showed that people were two to three times more likely to actively manage their investments, selling off deadbeat stocks and buying better-performing ones, when they used the Orb. This is the psychological paradox of ambient information: We’re more likely to act on a subtle but continuously present message than an intermittent one we’re forced to stare at.

So here’s the radical idea: Maybe the real killer app for ambient information isn’t alleviating data overload or tracking investments. Maybe it’s taming global warming. To improve energy efficiency and reduce emissions, we first need to make omnipresent the hidden facts about our usage — paint them on the world around us.

After all, we already know we’re energy hogs, right? We talk about our personal carbon footprint, argue the finer points of buying carbon credits, tut-tut over Al Gore’s energy-bingeing McMansion. Ambient display of our actual usage might just get us to cut back.

There’s already solid evidence that feedback mechanisms can change eco-behavior. Think about how hybrid-car owners become obsessed with the dashboard display showing an on-the-fly calculation of gas mileage. The result? They change the way they drive, specifically trying to maximize mileage. It becomes a game, an enjoyable challenge, complete with quantifiable personal bests.

Here’s an even wilder idea: How about making our energy use visible to everyone? Imagine if your daily consumption were part of your Facebook page — and broadcast to your friends by RSS feed. That would trigger what Ambient Devices CEO David Rose calls the sentinel effect: You’d work harder to conserve so you don’t look like a jackass in front of your peers.

This isn’t as far-fetched as it sounds. The design firm DIY Kyoto (as in Kyoto Protocol) recently began selling a device called the Wattson, which not only shows your energy usage but can also transmit the data to a Web site, letting you compare yourself with other Wattson users worldwide. In a Borg-like way, users can see how much they’ve collectively reduced their carbon impact.

The hope is that it could spawn a cascade of conservation. It’s fun seeing your personal energy tab go down by kilowatts — but just imagine watching the world’s usage plunge by terawatts or petawatts. It would be like a global Prius, with millions worldwide tweaking the Earth for maximum mileage. Now that’s fun.