In the book new concepts and methodologies for designing of energy efficient and cost effective heating-cooling systems are given. Suggested principles of mathematical modeling, based on system analysis method, allow optimizing heating-cooling systems, integrated with buildings' thermo physical properties. New method for correct determination of heating and cooling demands of houses is developed. Energy efficiency of solar house-collectors are analyzed. Fundamentals and method for determining of real parameters of heat pump cycles are developed. High efficiency heating-cooling hybrid system, consisting of newly developed gas mixture-sourced heat pump and heating boiler is suggested. Method, developed for analytical defining of required lengths of closed and open loop geothermal heat pumps can help for correct designing of heating-cooling systems (including district system) sourced by geothermal heat pumps. Ice storage geothermal heat pump heating-cooling new system was developed, investigated and optimized. Comparison of efficiency of different systems to be used is accomplished. The book is useful for engineers, designers, researchers, and students of energy related universities.