It's just a small solar panel with charger/controller and battery. I've seen some ridiculously priced $1,000 with 100W solar and battery looking like 80-100AH. That panel costs $120, a good charger $40, total $160 with jumper cables. Merely 6 times cheaper than their gizmo :).
If you want some small easy solar and don't know how, or afraid to drill holes in plywood roof - buy portable solar kit at Solar Blvd or "solar suitcase" from Renogy, either one will be 100W or slightly more, and will cost under $400.
Kits with 20-25W panels are "maintainers", for keeping rig or truck in storage. You can't boondock with that.
100W panel "might" generate enough to keep battery from discharging too low over weekend, not on all days and not for every energy appetite, but possible.
With some care, 300W solar in Tx should be enough without getting involved with gasoline generators. As long as you don't need air-con.