The residential dwellings and other buildings which will be part of the demonstration programs referred to in sections 5503, 5504, and 5507 of this title shall be located in a sufficient number of different geographic areas in the United States to assure a realistic and effective demonstration of the solar heating systems and combined solar heating and cooling systems involved, and of the dwellings and other buildings themselves, in both rural and urban locations and under climatic conditions which vary as much as possible.

Consideration shall be given to projected costs of commercial production and maintenance of the solar heating systems and combined solar heating and cooling systems utilized in the demonstration programs.

Encouragement should be given in the conduct of programs under this subchapter to those projects in which funds, appropriated by any State or political subdivision thereof for the purpose of sharing costs with the Federal Government for the purchase and installation of solar heating or combined solar heating and cooling components and systems, are committed before or after September 3, 1974.