Accurate prediction of electricity generation from renewable sources is an essential element to ensure the stability of electricity systems and the transition to more sustainable energy production. The study aims to optimise the operation of Ukrainian power systems through the introduction of the required share of renewable energy sources to ensure the reliability of the power system. To study the accuracy of forecasting electricity generation by photovoltaic power plants in Ukraine, data analysis, a review of existing forecasting models and methods, and comparative analysis using satellite images and meteorological observations were used. Low accuracy of forecasting output is a feature of electricity generation from renewable energy sources, which is explained by the random nature of energy sources and related meteorological conditions. In Ukraine, the problem of qualitative forecasting of electricity generation from renewable sources is becoming more relevant. The importance of finding effective methods for forecasting electricity generation in Ukraine has increased with the emergence of the electricity market. This study addresses the issue of forecasting electricity generation by photovoltaic power plants for the day ahead in the conditions of the Ukrainian energy market. As part of the study, the issues of Ukrainian legislation regarding the requirements for the accuracy of electricity generation forecasting and the consequences of their failure were considered. The study also reviewed modern models and methods for forecasting electricity generation by photovoltaic power plants and explored the new “forecasting system market” in Ukraine. The study presents accepted forecasting metrics that allow estimating errors and comparing the effectiveness of different forecasting methods. Considering the dependence of electricity generation forecasting on meteorological parameters, a comparative analysis of forecasting accuracy using satellite images and meteorological observations was carried out. The study will determine the material presented in determining the model for forecasting electricity generation, thus increasing the efficiency of energy companies in the conditions of the Ukrainian energy market. The study will also reduce the negative impact of the energy sector on the environment and contribute to a more efficient and stable electricity system in the future