If you are concerned with having power when the grid is down this Mini Solar Power Plant project will allow you to build a that will help you out in a pinch.
“Arduino fan Kurt (from Kurt’s Arduino Projects), designed his ‘Mobile Sun Tracking Solar Power Plant to keep civilization running smooth. To get the solar panel to track the sun, Kurt used a cheap (little more than $1) LED flashlight and replaced the LEDs with three LDR photo sensors (each with their own shade).”