Re: A very confusing subject
"Check out this solar energy map for the USA:
The problem I see with this is that solar energy is given as Watt-hours per square meter per day. That is a measurement for electricity, not radiation. In other words they were measuring electricity produced. My mistake may be that I was not taking into account the efficiency of photovoltaic panels (perhaps 18% efficient). That might explain the confusion here."
I don't think it's electricity produced- numbers are too high. (Roughly, 12 hrs of daylight per day divide by 6000 watts gives 500 watts per hour per sq meter).
And there is information missing from the graph e.g. is it a yearly average or a average in some month (winter or summer)?