First off, since a picture is worth a thousand words, see my 4 customer images (uploaded by 'Nick'). For such a small package, (about 8"x8" square and 1" thick including the handy pocket), this thing really works well. It will even charge your devices indoors under the right kind of lighting (halogen or incandescent work surprisingly well, while fluorescent does not really work much at all). I didn't upload any pictures showing its power output from indoor lighting as most people will not use it this way. However, if you're going to have a light on anyway, why not put it to good use charging one of the many electronic gadgets we all seem to have these days? Power output: In the pictures I uploaded, you can see a tree and two cropped images of my multimeter Equus 3320 Auto-Ranging Digital Multimeter screen. (This is a great all-around meter too!) To connect the two metal meter probes to a solar panel with only a USB output was done by cutting the proprietary connector off of an old USB cable for a device I no longer owned, stripping the wires inside (black and red only--that cord had no data wires), connecting those black and red wires in the USB cable to alligator clips and then to the probes on the multimeter. Then I simply plugged in the male end of that sacrificial USB cable to the panel. Is there the potential for power loss doing it this way (thus skewing my results to the conservative side)? Yes. Is it cheaper than a dedicated USB power meter. Yes. Alright, for the nitty-gritty details: Indoors, you can probably expect about 4.5-5.5V and 0.25A (obviously depending upon lighting conditions) Outdoors: Cloudy conditions with a thunderstorm rolling in: 5.87V and 0.39A, giving you 2.29 watts Mostly cloudy conditions: 5.67V and 0.512A, giving you 2.903 watts Mostly sunny conditions: 5.76V and 0.694A (a separate reading yielded 0.72A), giving you 3.997 watts Full sun conditions: 5.66V and 1.047A (wow!), giving you 5.92 watts **There is a label directly on the panel I received that says it's rated for 3.5 watts, so maybe the manufacturer takes some sort of average of many types of conditions? I think the Amazon detail page for this panel says something like 6 watts, and in fact there is another identical panel sold by another Amazon seller that they rate for 6 watts, but it's almost triple the price when you factor in the discount you get for purchasing the battery power pack along with this panel from EasyAcc. Build quality: Pretty impressive; seems to made of ballistic nylon with snaps that click with authority and metal-reinforced holes at each corner to attach it to nearly anything your imagination can come up with. There is a female USB cord that pulls out of the pocket, and plenty of room to hide a cell phone while it's charging or a portable battery pack. Note: I purchased this panel with the EasyAcc 12000mAh battery pack EasyAcc 12000mAh 4 USB External Battery Pack Charger Power Bank For iPhone 5 4S 4 3GS; iPad Mini, iPad 4 3 2; Android Tablets:Samsung Galaxy Tab 2, Note 8.0 10.1; Google Nexus 7,10; Microsoft Surface Pro ; Acer B1; iPod; Android Smartphone: Samsung Gala...], which is also an excellent product, although it's too long to fit in the pocket on this solar panel. EasyAcc had (and still appears to have as of this writing) a deal where you could get something like 40% off of this panel if you purchase one of their other qualifying products, hence the battery pack. The panel is already a great deal on its own, but the discount makes it almost a steal. A note on using this panel by itself or with a battery pack: It's recommended that you connect this panel to a battery pack and then connect the battery pack to your device (phone, tablet, etc.). The reason for this is simply because the intensity of the sunlight hitting this panel will naturally vary with cloud cover, the position of the sun in the sky, etc. As such, whatever you're charging with this panel will receive a variable level of current and voltage. On many devices, this is not an issue (because of internal charge controller circuitry), but many have said that if the level of current flowing to an Apple i-device dips below a certain threshold, the device will stop charging and display an error message about the charging cable not being compatible, or something of that ilk. Sometimes that message will go away on its own and start charging again. However, you may end up having to go over to your i-device, unplug the charging cable from it and then reconnect it. Having to babysit your device while it charges hardly seems worth the effort. By using the panel to charge a battery pack and then using said battery pack to charge your device, you're ensuring that the amount of current and voltage being output to the device is as consistent as possible. Even though it's not really close to the same thing (DC vs. AC for one thing), that's the same reason home solar and wind power systems feed a battery bank which then powers your household devices via an inverter. Of course if you're in a pinch and have a dead phone and this panel but no additional battery pack, this panel is gonna save the day. Excellent for camping, hiking and anywhere else you don't have access to conventional power sources but still have USB-powered devices to charge. For the money, this is definitely one of the most effective solar panels (power per dollar) you can buy.