Urgent need to reduce emissions of carbon and other harmful substances in order to combat climate change is becoming more acute every year. Research presented in this work has the main goal of drawing additional attention to the technology of delivering daylight to rooms with constant presence of people, animals, and plants, which allows us to relieve some of the problems of energy and environment, for example, by reducing volume of electric lighting. This paper presents a detailed study of efficiency of light beam passing through a mirrored hollow tubular light guide, on basis of which the derived mathematical dependencies, calculation tables, necessary for practical work when modelling energyefficient lighting systems, based on mirrored hollow tubular light guides, are presented. In addition, energy levels of the light flux were studied, as a result the energy efficiency resources of lighting systems were identified and directions for possible practical application of these resources formulated.