These are good solar days.

This fall, we installed the passive hot air panels. Through the fall and early Winter, they weren't as efficient as they could have been, since they were shaded by some oak trees that refused to drop their leaves. In the dead of Winter, we had a lot of grey days so the output was 'spotty' at best. But now that the Sun is back and the trees are bare, they are putting out all the heat we need and then some.