Editing Passive solar building design (section)

==Efficiency and economics of passive solar heating==

Technically, PSH is highly efficient. Direct-gain systems can utilize (i.e. convert into "useful" heat) 65–70% of the energy of solar radiation that strikes the aperture or collector.

Passive solar fraction (PSF) is the percentage of the required heat load met by PSH and hence represents potential reduction in heating costs. RETScreen International has reported a PSF of 20–50%. Within the field of [[sustainability]], energy conservation even of the order of 15% is considered substantial.

Other sources report the following PSFs:

*5–25% for modest systems
*40% for "highly optimized" systems
*Up to 75% for "very intense" systems

In favorable climates such as the southwest United States, highly optimized systems can exceed 75% PSF.<ref>{{cite web |url=http://www.nmsea.org/Passive_Solar/Passive_Solar_Design.htm |title=Passive Solar Design |publisher=New Mexico Solar Association |access-date=2015-11-11 |url-status=dead |archive-url=https://web.archive.org/web/20151201213855/http://www.nmsea.org/Passive_Solar/Passive_Solar_Design.htm |archive-date=2015-12-01 }}</ref>

For more information see [[Solar air heat|Solar Air Heat]]