This paper makes an analysis of the principles of energy saving in buildings, regardless of the aim and intended usage. The survey that yielded from the analysis of available and scrolled literature, is presented, and classified by energy methods usage and their results. Also, the main tactics in design, construction and renovation are considered, related to the heating, ventilation, and air-conditioning systems, the envelope systems with thermal insulation for exterior walls and roof, the shading devices, the intelligent lighting, and the usage of high-level energy saving appliances. Finally, the authors summarize these main methods or technologies that exploit analytics and digital service capabilities and resources used for a strong impact on energy consumption decrease in buildings, as outcome.