Dissertation investigated the combined solar heating system efficiency aspects as a prerequisite for the efficient operation of Latvia’s climatic conditions, thus increasing energy independence, reducing heat production’s negative impact on the environment, and promoting consumer comfort and quality of life. The goal is to develop a methodology for a combined efficient solar heating system for Latvia’s energy production. To implement this goal, the following objectives have been advanced: to explore the functional arrangements, to identify the factors that affect high energy efficiency rate of change, and the combined heating system efficiency to cover the heat demand of consumers, taking into account the development of the energy system, and to define a variety of other factors on the optimal heating scheme selection and methodology. To develop and experimentally verify Latvia’s conditions for a suitable combination of solar energy systems, analyze its performance in simulation and economic optimization of the system defining the various measures and technical solution application. In this thesis studies are based on the author's practical, experimental research experience working with the Institute of Physical Energetics Solar Energy Resources Research Laboratory site. For studies, the voluminous data accumulated in IPE material on the actual climate data and solar panels indicators was used. The author carried out the experimental measurements and theoretical summary of the results of the single methodology for structuring the flow diagram with a mathematical model. Thus, the thesis of a scientific innovation of a complex system of mathematical modeling using the experimental data obtained, thus making the calculation methodology most accurate and close to real conditions. The thesis, the developed methodology and conclusions of a practical application for engineering work in the design and implementation of the modernization of existing combined systems. The research results have been reported 13 times in international scientific conferences and are reflected in 27 publications. The doctoral thesis consists of 5 chapters and its volume is 118 pages, which contain 47 images, 15 tables. The study uses 89 literature sources.