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I have tried an x-dragon 40w and allpowers 80w solar panel, both claim they can charge a laptop. I have a netbook that has a power brick of 20v 2a. The 40w and 80w panels both have a plug that fits and claim 18v 3a output. For a second when plugging into the netbook it flashes that it's charging, about 10 seconds later it comes off. After leaving plugged in all day, no % increase, rather a decrease (slight due to turning on/off). I also tried to charge a guggha battery bank that has 2 inputs. Micro USB and DC (varying). With the micro usb it will charge at 2a or about 8.5-9.5w varying as shown on its lcd screen. When plugging the DC in, it does not charge at all, the backlight of the power bank flashes on and off, and the charge indicator on the screen goes on and off, and the wattage indicator never comes on to show any incoming amperage/wattage. In short, beyond getting a 20-30w rated USB only panel, solar is quite worthless unless you get 100w panels and hook up to a large heavy battery. I now have a few 21w solar panels with dual USB and those work just fine for charging power banks and cell phones at 5v 2a speeds. The 21w panels were around $29. Anything larger is just throwing money away. Hope this helps other people new to looking into solar like I was. My next step past the cheaper 21-28w panels (5v usb x2) is to go with a minimum of multiple 100w panels for ~$1 per watt.