Yeah, it consumes roughly 9% of the panels; or 18 watts over the two. In reality, no panel performs at full capacity, so with the bar in it performs @ roughly a peak of 160w. The good news is, the bar is key/quick release and can be removed in all about 3 seconds. The idea is: haul your kayak, storage container, whatever, to camp and in the event that you need the extra 18 watts (typically you don't unless you are running high power stuff like an electric blanket), you unload and remove the bar. These things are built for versatility and this gives you options. For example, bar in, with two panels, you can run all accessories and the fridge full time. Overlanding is all about modularity and options; especially in a small form factor like a JKU.
Correct me if I'm wrong, but from everything I know and my personal experience, the issue isn't the percentage of the panel that is covered. Solar panels are made of individual cells that are connected in rows - power runs from one end of the panel, through all of the cells and to the other "end" of the panel. Shade blocks this connection, along the lines of a clog in a drain pipe. Therefore the shade negatively affects the output of all of the cells positioned before the shaded area in the connection. Eg. when I put my arm across a 100w panel under full sun, the outlet drops from 5amps to 1.2amps (roughly).
That's cool - I've never experienced a roof rack that's that easy to take off/put on. And yeah, with only a small 12v draw I can imagine it wouldnt end up being an issue. Anyways, enough of my distractions - cool rig and best of luck with the sale! I appreciate the willingness to chat.
Ha! I'd love too, but I wouldn't be able to sleep at night taking advantage of you like that.