I designed and built these two eight-foot by six-foot passive solar heating panels for installation in 2007. They have been adequate to maintain an indoor temperature above 65°F/18°C since that time - even though outdoor temperatures in winter dropped below -20°F/-29°C and even though the nine-foot by nine-foot overhead door has been opened briefly every morning and every evening.

Before the end of 2009 the panels had saved more than their purchase price in fuel costs and the owner expects that the future savings will exceed the original cost of the entire structure.