You can harness the power of the sun's rays to charge your electric vehicle. Here's how many solar panels you'll need to do ...

the energy she produces is free. A solar-powered calculator. Its solar cells are just above the buttons, on the right. These cells generate the energy needed to make the calculator work.

MORE: Solar energy pros and cons If you’re closer ... We suggest using NREL's PVWatts Calculator to estimate your solar installation costs. Project Sunroof is a free online tool to figure ...