When I was a teenager I bought solar cells from a catalog and mounted them on top of my portable radio. It worked pretty well and was popular on the beach. I ended up in the middle of the dessert with a dead cell phone battery and had to use a 60KW generator to charge my Cell phone. I bought and carried a USB solar panel with me after that. Over the years those USB panels got a little bit bigger and a lot more efficient to where they’d push a couple amps so I gave them to my siblings for emergencies. The bigger panels 80-100W were getting reasonably priced so a couple years ago (2012 ish) I started buying them a couple at a time until I had twelve of them in storage. When I quit my full time job in 2017 I laid one of them on the roof in the winter for a couple days to gather some data. One of my requirements is to provide 200WH of power for my CPAP. I have enough battery for a couple days, but going without it is not an option. After a couple days I found out that one panel in the winter sun was not going to provide enough power. I grabbed a second panel and bolted them together making a 200W 36V array that should provide approximately 360WH of power per day in December. (The worst month.) Since I sleep at night the power has to make a round trip into and out of a battery which has a significant cost. But I can also live on six hours of sleep if I have to. During the summer months those two panels produce almost 900WH/Day which can keep our refrigerator powered and have enough left over for Cell Phones and charging lanterns for the evening. It is my opinion that all homes aught to have these two panels to provide USB power for the occupants during an emergency. If your a bit of a Macguyver, 200WH is enough power to make a pot of coffee, toast a couple bagels or thaw waffles with a microwave.