Evaluating Our Solar Site

We’re likely to get solar panels this fall, so I’ve begun to evaluate the site where the panels will go. Most of our sunny grounds are given over to the garden, greenhouse, and our solar hot water system. The south side of our garage, though is perfect.

What I wasn’t sure of, though, was which part of the roof would give us the most sun each day. Yesterday, I took a photo of the roof every hour on the hour from 9 a.m. to 4 p.m. Below you can see the progression of shadows across the space (read from left to right, top to bottom for chronological order).

I popped these pictures into Libre Office Draw and superimposed each shadow onto a single image of the roof. I added a 20 percent shade to the space.


It is a little clearer without the roof underlaying the image. Without the roof, the shaded spaces add up and the darker spaces have more shade than the lighter ones.


Finally, I created a topographic-style image of the solar resources, showing how many hours of sunlight hit each spot of the roof. I added measurements to help show the scale.


The best time for solar panels is 10:00 a.m.–2:00 p.m. This means that most of the center and left of the roof  are in full sun during this time. Really, anywhere in the dark grey “7 hr” zone would be a good spot.


In total, we have 260 ft² of space with 6 or 7 hours of full sunlight.

2 thoughts on “Evaluating Our Solar Site

Leave a Reply