Solar Power in Seattle - Why Not In Alabama?

Scott and Carolyn Sherwood's Home - Founders of http://www.solarpie.org

My sister in-law Linda Nelson's home

Back from my Seattle, Washington vacation. Above are pictures of homes being powered by Solar Energy in Seattle. Each house was producing more energy via solar energy, on the cloudy day I was there, than they were actually using. These pictures beg the question. If solar power is viable in cloudy/rainy Seattle, Washington - why can't it work in Alabama?