Purpose: The paper aims at a comparative analysis of the ways in which Polish energy companies and selected international corporations manage their financial surplus. Design/methodology/approach: The paper is theoretical and analytical. It presents a critique of pertinent literature dealing with the essence of the financial surplus and its place in the theory of capital structure determinants. The empirical data used in the calculations were taken from a Reuters database. Based on data for the years 2010-2021, relationships were calculated showing the specificity of the energy industry and the use of financial surplus to finance operating activities, investments in tangible fixed assets and the possibility of debt repayment. Findings: The research led to the conclusion that Polish energy companies and their international counterparts are characterized by a high share of long-term assets in their total assets, which means that the rate of return on assets is relatively low. Polish energy companies manage their financial surplus employing methods that are not fundamentally different from the same in their international counterparts. Only the ability to repay debt from the surplus is higher in Polish companies than in the corporations used for comparison. This is due to the lower level of Polish companies indebtedness, which results from Poland’s interest rates which are higher than in the economies of the corporations selected for the comparison. In addition, foreign companies used the surplus to finance development to a greater extent than the Polish companies. Research limitations/implications: The energy transformation of the Polish economy is going to need large investments. Further research should determine the extent to which they can be covered from the financial surplus, and to what extent from capital raised on the financial market. The research presented in the paper is based on historical published data. Future research can attempt to compare forecast values. Polish companies have to implement a number of investments in the area of renewable energy sources, modernization of transmission lines and construction of nuclear power plants. In order to meet the needs, they must select rational financing sources. To finance these investments they should use their surplus more extensively, while at the same time limiting its use to finance operating activities. Practical implications: The results of the research can be used by the managerial staff of Polish energy companies to take action and use their surplus to finance various areas of activity based on patterns positively tested in international corporations. The results of the research can also be used by doctoral students and students conducting their own research and writing papers. Social implications: The results of the research may increase awareness of the need for energy transformation and rational selection of financing sources. Originality/value: The results of the research show stakeholders interested in the industry how Polish energy companies used the financial surplus. The value of the surplus reflects the company's ability to repay its debt, and thus its ability to raise external capital to finance its investment. It also shows whether Polish energy companies will be able to finance the implementation of the energy mix and cope with challenges arising from the Fit for 55 package.