# Adjusting the angle of PV panels on a roof



## K.B. (Sep 7, 2012)

Hello all,

First off - thank you for all the info posted in this forum. I've been browsing through the current and older threads and have learned quite a bit.

I am looking at options for installing a PV system for our home this coming Spring/Summer and have a question regarding adjustments of the panel angle relative to the sun...

For those of you with panels mounted on a roof or other fixed mount, how often do you find yourself adjusting the panels to try and optimize their angle relative to the sun?

I have a standing seam metal roof with a 3/12 pitch, so if I were to install the panels "flat" on the roof, the angle (relative to vertical) would be ~75 degrees. This is pretty close to ideal for June, but way off for Dec, where ~25 degrees would be ideal. My latitude is ~42.5N.

Generally, I'm trying to get a feel for whether it would be better to install the panels on a fixed mount rack where I think it may be easier to adjust the array as one unit, or mount the panels directly on the roof.

Thank you for any help or suggestions.


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## wy_white_wolf (Oct 14, 2004)

Latitude is ~45 for my cabin in MT. I built mine to have 3 settings 30, 45, 60 degrees. Had planned on adjusting it every 3 months but after running some calculations determined it was only worth it to adjust twice a year on the equinoxes.

You can use PVwatts to give you an idea as to what the differences are in production.

http://www.nrel.gov/rredc/pvwatts/grid.html

WWW


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## SolarGary (Sep 8, 2005)

Hi,
I came to the same conclusion as WWW -- its probably not worth the extra complication. Probably even less so now with lower PV module prices.
PVWatts will tell you -- just run it for tilt equal latitude, and then fro 15 degs more (winter) and 15 deg less (summer).


Gary


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## K.B. (Sep 7, 2012)

Thank you very much, WY White Wolf and SolarGary. 

I ran a few calculations on the PVWatts tool and it does indeed look like there is very little difference for the range between 45-75 degrees for the array tilt (from horizontal).

My main concern for efficiency is for the winter season. Almost every day in summer is sunny and clear in my area, while we can easily go 5 days without seeing the sun in winter...


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## wy_white_wolf (Oct 14, 2004)

Unless you're off-grid it would be better to maximize for summer. As you point out, with that much cloud cover there just isn't that much energy available in the winter in your area.


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## K.B. (Sep 7, 2012)

The house is off-grid, so we'll be trying to squeeze every watt possible out of those panels!


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