This article discusses the problems associated with physical and hygienic studies aimed at determining the influence of insolation – an important climatic factor – on the light, radiation and thermal regime of buildings, and territories in urban development. The article proposes the design of an insolation device of a flatbed type, known as a Svetoplanograph‑2, which can be widely used in solving architectural, construction, urban planning, and energy problems in summer in regions with a warm climate. A method of step-by-step assessment of the insolation-light-thermal regime of buildings and territories with a complex morphological structure of buildings, which is a model of the energy characteristics of insolation, has also been developed. The use of a tablet-type device makes it possible to solve practical urban planning tasks, providing an opportunity to calculate and evaluate the quantitative and qualitative characteristics of the insolation regime in order to improve the environmental and climatic situation in urban buildings and development in the summer. The developed method of forecasting the insolation regime using a tablet-type device is the basis for modelling the energy state of insolation in a human environment in buildings and territories of cities with a hot climate.