In conditions of economic and political instability, when unpredictability affects business, the need for security, including financial security, becomes particularly important. In our study, we address this issue, with the main objective of comparing and evaluating the financial security of small and medium-sized renewable energy companies in Poland according to sustainable development goals. In order to study and describe relationships between selected groups of companies, financial ratios were used, including canonical variate analysis. The liquidity ratios of the surveyed companies indicated a low level of financial security in terms of the ability to meet short-term liabilities. The profitability of operations was low and did not contribute to the improvement of financial security in most of the companies. The lowest return on assets was found in the group of biogas plants. Higher profitability of assets was found in solar power plants, including those with system installations. Solar power plants were also characterized by a high level of total debt and a rapid turnover of assets in comparison to other studied companies. The results show that the financial security of small and medium-sized renewable energy enterprises in Poland is low, which may be a threat to sustainable development in the future.