"Every time the sun shines on the surface of a house and especially when it shines through a window there is "solar heating"...According to the NSF/NASA Energy Panel of 1972 the percentage of thermal energy for buildings supplied by the sun was too small to be measurable. ...Shouldn't we recalculate the energy consumption of every building assuming it were kept in the shade all day and... attribute the difference to solar energy? ...I would guess the average shaded fuel consumption to be 15% higher..."