I think so. A $ foot of 1/2" copper pipe pounded into a groove in a $ ft^2
of brown-painted aluminum roofing coil stock with a 1.5 Btu/h-F-ft^2 airfilm
conductance at 140 F in full sun in an 80 F sunspace with a $.50 ft^2 of GE
HP92W 10 mil R1 polycarbonate glazing with 90% solar transmission can collect
225-(140-80)1.5 = 135 Btu/h, at a cost of $.50/(135/3.41) = 8.8 cents per
peak watt, and people can sit in the sunspace, and the water heater's "waste
heat" can heat the attached house.