The European Union (EU) adopted a strategy for energy development and climate change mitigation. Its main goal is to become a "low carbon" economy with low greenhouse gas emissions, and a world leader in combating climate change. Under the conditions of extreme volatility in the energy market, especially of oil and gas, most EU member states are aware of the necessity of managing energy development, reducing import dependence and the rational consumption of energy, but without a negative effect on economic growth. In order to ensure new sources of energy and to reduce greenhouse gas emissions, the EU is focused on the greater use of renewable energy sources and the improvement of energy efficiency. In the last twenty years the EU member states have been working on the creation of the internal energy market and Energy union. The package of measures for the Energy union aims to ensure to the EU, and its citizens, a favourable, safe and sustainable energy. Many EU member states are largely dependent on a smaller number of suppliers, particularly regarding the gas supply, which makes them sensitive to energy supply disturbances. In addition, energy infrastructure in Europe is getting old and energy markets, especially cross-border markets, are poorly integrated. In line with EU goals agreed in the framework of climate and energy policy by 2020 and 2030, the EU should reduce its overall dependence on fossil fuels and reduce greenhouse gas emissions. The EU reform model has a large impact on the reforms carried in post-transition EU countries, especially in the power sector. Given that energy in many countries is crucial for the economic growth process, the question is whether all energy sources have an equal impact on economic growth and what is the difference in the use of particular energy source between developed and post-transition EU countries. The aim of this doctoral dissertation was to analyse the impact of renewable and non-renewable energy consumption on economic growth in developed and post-transition EU countries, and to determine whether there is a convergence in growth of energy consumption rate between the post-transition and developed EU countries. By using static and dynamic panel analysis on a set of 15 developed and 11 post-transition EU countries, it has been proven that energy consumption has a positive and statistically significant impact on economic growth. There is evidence that changes in the consumption of renewable and non-renewable energy sources per capita have an impact on economic growth in both groups of countries. However, in post-transition EU countries consumption of non-renewable energy sources has a negative impact due to changes in the structure of total energy consumption and decreased energy intensity. In the case of the developed EU countries, the consumption of renewable energy per capita is higher than in the post-transition EU countries due to the higher proportion of renewable energy in total energy consumption. There is also evidence that post-transition EU countries converge to the rate of growth of energy consumption in developed EU countries. These findings are the basis for further research in this area, and the results presented in dissertation can be used by energy policy holders for the development of the energy sector in the function of the economic growth of the EU.