The Goal Zero PV panel is rated at 20 Watts. Specifications here
Here is the average insolation figures for Houston
The line in the 4th chart titled "Insolation, kWh/m²/day" gives the kWh per square meter per day ~= hours of equivalent full power sun. You'll see that Houston average about 4 kWh/m^2/day. That means that an eg 20 W panel will produce about 4 x 20 = 80 Watt hours per day maximum.
If you average 4 hours of equivalent sun per day annually and if you use 100% of the panels output (which you won't) then at $0.12 unit:
Watt-hours/day = 20 x 4 = 80 Wh = 0.08 kWh/day
kWh = units per year = 365 x 0.08 = 29.2 units.
Value of energy in mains electricity equivalent at $0.12/unit =
29.2 x $0.12 = $3.50
That may sound wrong.
Actual amount will be less due to matching panel to load, not steering panel toward ssun etc.
Goal Zero has come close to achieving its goal - at least as far as the amount of energy provided goes. Such systems are valuable when grid power is not available but utterly uneconomic when grid power is present.
[FWIW: I design small solar lighting systems as part of my 'day job' so I'm confident that the results are 'in the order of correct']