Solar panels have become cheaper and more efficient in recent years, but you can't say the same for the big, costly inverters turning their energy into usable electricity. Google isn't happy with this lack of progress, so it's about to launch the Little Box Challenge, an open competition to build a tiny (and consequently cheaper) solar power inverter. The search giant is promising $1 million to whoever cracks the problem, although it warns that this won't be easy; don't expect to reach a breakthrough in your basement. If someone does produce this miniscule power box, though, it could lead to eco-friendly energy in places where it's currently unaffordable or otherwise impractical -- whether it's a remote village or your own rooftop.

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