Don't worry about it. It didn't come across that way to me.
Besides, I never went through with solar, just did the calculations. You at least have real world experience to prove book learning isn't always right.
It did make me think though, so this morning I tried to track down where I got my various information from. I think the majority of it came from these two threads, and the embedded links within them:
Charging Batteries With Solar Panels
Ontarians using solar to charge batteries
I remember I had started from those and was looking to figure out a formula to calculate what size solar I'd need.
I then ran through a variety trying to figure out a 30% efficiency rating (as per the info I was given) over 24 hours, compared to a constant current draw over 24 hours. When I put it all together, I got back 40W per amp rating averaged over the day. So, if the load on the TT averaged out over 24 hours was 2 amps per hour, then I'd need 80W of panel.
So, for panel output I think I used:
X W *.3 = 0.3X W / 12V = 0.025X A * 24H = 0.6X Amp replenished per day.
And for load I used:
Y amp rating * 24 = 24Y Amp used per day.
Assuming I wanted to replenish what I used, putting the two formula's together I got:
0.6X A = 24Y Amp
Solved that to be:
X = 24/0.6 = 40
So, 40W of 12V panel to replenish 1 Amp (averaged over 24 hours) at an assumed panel efficiency of 30%.
Problem is, I know I didn't just take Herk's word for it with that 30%, I do remember consulting some solar charts that seemed to confirm that was the right coefficient for a flat mounted, non tracking solar panel in my area (near Detroit), but for the life of me I can't find those now.