[beAbU]

Buy 2x extra panels. Honeslty the gains you might get by optimising panel placement (beyond matching to your hemisphere and latitude) will be outweighed by the additional cost. Domestic applications is not big enough to really give you significant gains in this department.

Make sure they face the right way (south for Northern hemisphere), and match the angle with your latitude. If you have a pitched roof thats +-10 deg in the correct angle, just lay them flat on the roof.

Edit: forgot to add, a while back there was an article here about a company that proved it was viable to lay the panels flat on the ground for massive solar farm installations. The savings from less installation labour and materials went to installing more panels. And they still came out ahead. Solar is getting cheap enough that the math gets weird. Your answer is almost always "just add more panels" unless you are seriously space constrained.

[vosper]

Thanks, that makes sense.

I don't know anything about rooftop solar mounting systems, I will show my ignorance here: I was imagining that perhaps you could attach the panels to rails running vertically rather than horizontally, to allow for convection airflow below the panels.

Or if the rails are horizontal perhaps they have holes in them to allow some airflow.

I'm sure this has been thought of and doesn't work some obvious reason I just don't know about.

Edit: As I expected, this has been thought of: https://solarstone.com/blog/natural-ventilation-and-effect-o...

[beAbU]

Your installer will know best :)

Make sure you design a roof with the rigt heading, and slope. The rest will be done by the installer.

My rails run horizontally, but thats only because it required less rail and mounting hardware compared to vertically. The panels are mounted portrait, in a 5x2 square. Each panel has 2x rails under it, so 4 rails horizonfally on my roof. If you sketch it out then it'll make sense.

Had I gone with vertical rails, each column would've required 2 rails, so 10x rails vertically mounted on my roof.