Solar panel direction

Hi,
I have my solar panels on a few out building some are horizontal and some are vertical,
What is the best way to have them, or doesnt it matter?
Thanks very much,
Phil.

http://re.jrc.ec.europa.eu/pvg_tools/en/tools.html#PVP
Whatch this link, click on your location on the map, and check Optimize Slope and azimut, in the summary output it will give you optimal inclination.

Regards

Hi Bigfilly
If youre referring to your portrait or landscape orientation it makes no difference.

I think the only reason they are mounted 'portrait' instead of 'landscape' is the cost of mounting hardware.

However the thought does cross my mind that a panel mounted 'landscape' is more likely to be partially shaded for a longer period of time. Partial shade can have a huge effect on output voltage and efficacy, unless you are using an MPPT charge controller.

With the vertical orientation, you may want to keep the terminal boxes at the "top" so the cable exits face downwards (assuming that's how they work on your panels), may help reduce chance of water ingress into terminal box....

Any panels connected in a group should be at about the same tilt too.

I was referring to the portrait and landscape positioning (thanks JON) but the link was helpful (thanks JESUSANGEL)
I have the 14 panels in landscape and 3 for the pcm60x in portrait, I only ask as the landscape ones are angled at around 25 degrees (I know its not perfect) and even though the sun is up and hot, they only make 400-700w until just after dinner and they get up to 2kw (which is more than I need) so I think that GEEK has it spot on, even though there not in the shade they still suffer from some sort of shade,
I have to move them eventually, so I will rehouse them in portrait,
Thanks everyone.