2 Panels Instead Of 3?

[chem geek]

If you are at a very northern latitude where the sun is not very directly overhead in the summer, then angling the panel will help. However, the effect is rather small until the sun is quite a ways away from being directly overhead (at noontime). The loss in heating goes as the cosine of the angle difference between the incidence of the sun and the perpendicular of the panel.

For example, if the sun is 20 degrees away from directly overhead, then you get about 94% of what you would get if your panel were angled 20 degrees to "point at" the sun. If the sun is 40 degrees away from directly overhead, then you get about 77%. I'm ignoring any positive effect from ground heating that Carl mentioned and that may more than make up for the loss during the day.

Richard