Solar Novice seeking advice

[Chris Jacobson]

Hi. This is my first posting. I'm considering a MicrFit (Ontario) solar project for my rooftop and I have a concern with some morning shadowing from about mid September until mid April. There is a 60' mature silver maple in another yard about 70' from the southeast corner of my roof (tree to the right in photo below). I have created a very detailed Sketchup model of my home and surrounding yards. When I project the model throughout a year cycle, the maple tracks a hazy leafless shadow across approximately 25% of my roof at the eaves from about 8:00 am until 10:15 AM. After mid April it's not a concern and I have absolutely no shadows from then until mid September when the cycle starts its seasonal repeat. The tree stubbornly drops its last leaves by mid November.

I have been speaking with a local installer who has quoted a 39 panel 9.3kw project all with Enphase micro inverters. The installer has presented projected revenue figures from PV Watts for this installation (roof faces south - 170 degrees, 6/12 pitch, Essex County Ontario Canada). I assume that the PV Watts projections are at optimal conditions so is there a way I can loosely estimate the amount of revenue loss I could expect from this shadow over a year? I just want to make sure it's not a project busting obstacle before we proceed. I expect the installer will do a full analysis but I want educate myself before that's presented so I can confront their figures. Also, is it a good idea to get an independent analysis done before making such an investment?

I'll try to post a photo I grabbed from Sketchup but if that doesn't work it's also posted on flickr - http://www.flickr.com/photos/algonqu...er/5584110868/. It shows how the shadow looked yesterday morning (a bit drastic as the model tree has full foliage)

Thanks in advance for your input.

Chris
http://www.flickr.com/photos/algonquinpaddler/5584110868/http://www.flickr.com/photos/algonquinpaddler/5584110868/ by algonquin paddler (http://www.flickr.com/people/algonquinpaddler/), on Flickr

[Rob Beckers]

Chris, on the whole, the effect of the shading won't cost you more than a few percent overall (3% at the low end, 5% at the high end would be my estimate). For winter we like a solar window of 10am - 2pm, for summer it's 8am - 4pm. So for the most part those trees will be outside the solar window, and for much of the time there won't be leaves either. Not a biggy.

To calculate average energy production, set PVWatts to 75% overall efficiency, plug in your location, roof pitch, and roof orientation, then let it rip. With your roof pitch I would deduct December from the total yield (your roof will shed snow, but won't be great at it), multiply by 0.96 (for shading) and you should have a conservative number that's close to what you can expect.

-RoB-