The article contains a rough estimate of global investment costs that are required for the global energy transition to zero-carbon economy by 2050. The evaluations are based on the data on global energy supply and its forecast to 2050, assumption that all the global energy needs are to be satisfied only through non-carbon facilities, and data on investment costs per unit for the facilities that use different types of non-carbon energy carriers. The authors conclude that the total costs of the energy transition worldwide are some $120 trillion, and that achieving the goal of totally non-carbon economy by the middle of the century would require a sharp, two-threefold, increase in investments in energy supply comparatively with the modern level, including acceleration in development of hydro and nuclear energy.