It all depend on what and how many you hook up to the solar panel. They do cell phones and Ipods just fine for the most part. The bigger the panel the more power it can generate. The sun don't need to be out for them to work they do work with cloud cover just not as well. The brand makes a diff as well my buddies one took all day to charge an Ipod and mine did not the panels were about the same size. I can't remember which brand I had I sold it to one of the guys coming in as I was going out. Just shop for one like you would a generator the more amps it pushes out the better it will do.