I have the GZ smaller units, the "Guide 10+ power unit and the Solar 7 solar panel." I bought them last year and have only been fiddling with them. I have not had to employ them for any serious purpose, but I am quite satisfied with my purchase.

Although I do a fair amount of backpacking and bike touring, I didn't really buy them for that purpose. I will more likely be using the units when the power grid is down (earthquakes, most likely) and I want to keep batteries charged to run radios, flashlights, and GPS units. All of my devices use rechargeable (Eneloops) AA and AAA batteries and I am confident GZ can keep abreast of my demands when required.

I don't plan on hiking with GZ any time soon, since replacement, fully charged batteries are significantly lighter; reports from others indicate that solar panels mounted on backpacks do not charge very well.

So far, I am quite satisfied with them, and would recommend their acquisition if your contemplated needs are similar to mine. Do shop around - I have seen GZ at Costco; they are also available at REI, another of my favorite haunts.

I have no experience with their larger units, but based on what I have, I would expect them to be good. You are soon dealing with real money when you get into GZ's big boys