Installing a set of solar panels on the roof of your home can lead to significant savings when your monthly power bill arrives. But how do you know how well they're performing in between without watching the meter like a hawk? With this innocuous looking piece of art that doubles as a home energy monitor.

Students at Stanford University have designed an entire sustainable house called the Start.Home, and it's not just all about finding energy-efficient appliances and ways to get off the grid. It had to be livable, too, without requiring residents to spend every waking hour finding ways to conserve energy and resources.

The subtle wall-hung sculpture features a series of opposing wooden slats that fan out or slide together depending on how efficiently the home's solar cells are operating, and how much energy the house is consuming. At peak efficiency the slats all spread open like the petals on a flower, and at a quick glance it's easy to tell, day by day, when the system is working best, and when it needs some improvement. [Stanford University]