Input on Directions of the Panels.....East facing?

[Itsme]

I am told that South and West are the best orientation of the panels, as they produce during peak late afternoon and early evening hours. However, I am extremely space limited on South, and some shade limited on the West (I am going with a string inverter, for costs, and fewer points of failure on an owned system).

I have plenty of room on the East facing roof. I am told that East is least desired. Is that only because of lower power value in the AM, vs during peak late afternoon and early evening hours (I am on TOU pricing); or, is there a noticeable difference in Kwh production for panels on the East facing, vs the South or West facing?

Thoughts welcome

Thanks

[kad153]

If you are in the Northern Hemisphere, South is optimal and North is bad. My understanding is that East and West can both be good, depending on shading and how much of the day's sun will hit the panels at a decent angle. Usually a good installer comes out and tests your roof and will advise.

Is it possible your "south" roof is not truly 100% south, so your west roof is really a bit south-west, making your east roof a bit north-east? That's potentially a reason someone told you for your east roof may not be the best, although if there is shading on your west roof you may have to measure that as well.

[Itsme]

If you are in the Northern Hemisphere, South is optimal and North is bad. My understanding is that East and West can both be good, depending on shading and how much of the day's sun will hit the panels at a decent angle. Usually a good installer comes out and tests your roof and will advise.

Is it possible your "south" roof is not truly 100% south, so your west roof is really a bit south-west, making your east roof a bit north-east? That's potentially a reason someone told you for your east roof may not be the best, although if there is shading on your west roof you may have to measure that as well.

I am in San Jose, CA. Yes, my roof face (front of the home, where some panels would go) is not truly south; it has about a 20 degrees tilt to the West (clockwise, from horizontal); that is ideal, but is space limited so will get half the panels. Remaining options for the other half of the panels are...a) East facing roof (which is actually about a 20 degrees tilt to South; clockwise from the vertical); or, b) West facing roof (which is actually about a 20 degrees tilt to North; clockwise from the vertical). Which of these two option may be better?

Many thanks

[Volusiano]

I think east is less desired for the following reasons:

1. If you live in an area where there's frequent early morning clouds or fog that take a while to clear up by late morning or so.
2. If you're on a TOU plan. Most TOU plans have their on-peak time in the summer in the afternoon through evening, where west facing is better for max on-peak time production. Many POCO let you switch out of TOU plan back to the basic plan if you want out. This may help improve the value of your morning solar production.

But east facing alsohas a slight advantage -> panels operate more efficiently when they're cooler rather than hotter -> morning has cooler temperatures.

If your west facing roof is about 20 degrees tilted to the north, it may be an advantage in the summer time because I think while the sun is more overhead in the summer, it rises and sets from and to the north a little bit.

On the other hand, your east facing roof with 20 degrees tilted to the south has the advantage in the winter time because the sun is further south in winter.

But you can do whatif analysis using PVWatts to see what this means in terms of annual production in both cases and decide for yourself.

As for your shading issue on the west side, you'll have to judge how significant it's going to be to warrant placing panels on the west roof or not.