I see Harbor Freight has a 45 watt solar panel on sale for $200, not including inverter or battery, so that's right in the same ballpark, namely, too many years to recoup.
Yet, it's somewhat worth considering if you wanted to, say, have power at an outbuilding for occasional lighting or light-duty tools, versus the cost of running a power line.
The best of ZDNet, delivered
ZDNet Newsletters
Get the best of ZDNet delivered straight to your inbox



