The new solar air heater leaning up against the well/shower house where it will likely be installed as it is a near perfect south facing wall. Thermometer reading after just a minute behind the air outlet? 100 degrees and that's with outside air of 48. NICE! My guess is that this would easily heat our little shower house to a comfortable 70+ degrees on sunny days during the winter. A big thanks to Rick for building it!
Update 1: Went back out to get another temperature reading, 110 degrees! From what I've read online they can be expected to output air between 100-130 degrees or more on sunny days. Even on cloudy days they will put out air that will warm a space though obviously not as effectively.
Update 2: As of this update (1pm) it is 50 degrees outside and the current reading is 120+ (my thermometer tops out at 120) that's a 70 + degree gain.
So, cost on these, is 4x8 plywood, 2x4, paint, caulk, silicone, tempered glass assuming it is all bought new probably $100-150. My guesstimate is that in one winter the savings on electricity would be $300-500 depending on the use scenario. Cost on keeping our well/shower house heated to 50 degrees this winter has probably been $60-80, maybe more. To keep it heated to 75 for comfortable shower house temps would have been MUCH higher, easily $200+ as it would require an actual heater, not just the two heat lamps I currently use. Using the solar air heater, I think we'll be able to keep this structure heated to at least 75 on sunny days, for free next winter.