Bests & Worsts Reviews from Amazon

False advertising. This unit uses 6 sunpower square solar cells. Each cell is rated around 3.1W. Some claim 3.3W but there are 100W sunpower arrays which have 32 of these square cells on them. Be realistic. In any case, you will never get 21W from this unit. You will never get 20W, not even 19W.. There are 2 usb ports. If you use both of them, you will get 3A current max. Basically, this is a 5x3=15W solar panel. If you bypass regulator you can approach to 18W. You can find similar panels with exactly the same sunpower cells and 2 port smart regulator attached for $25 cheaper. This is just rebranding of some made in china solar panel. They just charge you $25 more for nothing. Really, nothing...on top of that, they lie. I asked Anker about their 21W claim. I asked "how am I going to get 21W out of this unit?" No one replied yet. I'm returning this. Charge whatever you want but don't lie to us!