Panel output: Watts and Volts

What determines the voltage output of a panel? I’ve seen 200W panels with Voc ratings ranging from ~20V to over 40V. The higher voltage would be desirable for me since I could hit my voltage target with fewer panels. Is there any downside to a higher V panel?

As long as your MPPT controller supports the higher voltage you’re better off with higher voltages to minimize power losses in your cables and you can use higher gauge wires which can save you a little bit of money.

I was thinking higher volts would be better, I just wasn’t sure what I was losing (if anything). Now, after looking at the specs, I see what should have been obvious to me from the beginning: for a given wattage, as voltage increases, amperage decreases. So a 12V panel will have a higher amp output than a 24V panel by a factor of 2, all else being equal.

Exactly, spot on! Long distance transmission with low volts and high amps is very expensive and inefficient, that’s why the large transmission towers carry hundreds of thousands of volts with much lower amps across smaller wires. Of course, higher voltages come with other downsides like electrocution risks and arcing.