The main problem of isolated areas of Tyva today is the lack of an effective electric power distribution system. The traditional way of solving theis problem is replacing older diesel power stations with the adjustment of their installed capacityies. AThe more attractive option serving to improve the electric power supply system of Tyva is the constructionng it with a focus on the local renewable energy resources. The solar energy, due to its reserves, availability, environmental safety, and usage scale, is the most important in the variety of renewable energy in decentralized parts of Tyva. To investigate the functioning conditions of using solar energy as part of an integrated electric power supply system it is necessary to study the modes of solar energy delivery. The indirect calculating methods for calculating solar radiation density on various surfaces are investigated in the article. The Byrd method was selected that gives the closest values to the observed actinometric station values. The monthly averages of the total amount of solar energy on a horizontal surface in the Tyva’s decentralized areas were calculated using the proposed method. A map dividing the Republic of Tyva into solar climatic zones as developed taking into account terrain with particular climates.