BTU Analysis REG - Version 5.1.0 The BTU Analysis family of programs are premiere heat load calculation programs. The BTU Analysis programs have been commercially distributed and are marketed through professional organizations, trade advertisements, and word of mouth. They are currently used in six (6) foriegn countries and the U.S. Used in temperate, tropic, artic, and arid climates. They have proved themselves accurate and useful again and again. The PLUS program is designed for general heating, air-conditioning, heat pump and commerical studies. The REG program is designed for general heating, and air-conditioning, and light commerical studies.