I am still playing with that Kill a Watt meter. Currently I have it plugged into my fish tank. Power for two lights and the water pump is at .33 kWH for a run of 14.21 hours. At that rate the payback for the system is 8.75 years.
But, I also have a lamp that I keep on in my office next to the tank. It’s a 60 watt bulb. So, if powered that lamp with the system the pay back duration changes. From 8.75 years to 2.42.
Maybe this solar power thing makes sense at the micro level.