Southeast or Southwest for mounting panels

[crb478]

I will soon be mounting about 400 watts of Solar on my Dock which has a hip roof with a pitch of about 8/12 or 9/12. Haven't measured but it doesn't matter as I won't be changing the roof pitch.

In my zip code, 28037, perfect Azimuth would be 187.8 degrees. My dock has two solar surfaces, one at 142 degrees, SE, and one at 232 degrees, SW. So neither one has a clear advantage, but I am leaning toward the SW view for better solar coverage.

By my calculations the SE view is 45.8 degrees off the perfect south facing view and the SW is 44.2 degrees off. Almost a equal split, but there is a little more shade from the SE.

It would however be much easier to mount solar panels from the SE side, the SW side will involve a boat ladders and moving water, as well as a slightly moving dock.

So for you experts are there any real advantages to SW over SE? The panels will be tilted at either 33.69 degrees or 36.87 degrees, where the best case scenario year round would be 29.5 degrees. I truly believe this will be at 33.69 degrees so only 4.19 degrees from ideal, worst case 7.37 degrees off.

Thanks for all advise and any calculations that would show the solar output differences for SW to SE

[shootist]

400 watts is one panel, add another if it doesn't do the job.
What time of day do you see the most cloud cover? Morning or afternoon?

[hclarkx]

As Shootist noted, cloud conditions in your area can make a difference. You can use PVWatts to get a good estimate of the energy production for each of your options. This estimate will take into account the weather patterns in your area. That includes time-of-day cloud events. If there's a significant advantage to SW, you might want to bite the bullet and go that route.

Though I also agree with Shootist that if you have the roof space, add an extra panel or two and go SE to keep life simple even if SW provides more per panel energy.

In my own case in Northern California, I had the option of east or west. East was a few percent better (morning sun was better than afternoon sun and I also had a bit less shading if I put the panels on the east facing slope). But, that side of the roof was cluttered with attic vents and skylights that complicated things. So I went west.

[crb478]

Thanks for the PVWATTS link, SE comes out slightly better and the more I tilt to true south the better. Its also the easiest side, so I will probably go that way. Thanks for the input.