The article presents the challenges faced by the hard coal mining sector in Poland. The biggest challenge results from a decrease in the demand for coal, which was triggered mainly by the climate policy, including the tightening of environmental standards and an increase in the efficiency of generating units. The fundamental model of the MRÓWKA domestic coal market has been described. The model allows for determining the marginal price of a given fuel for a given generating unit in the system and the optimal mix of fuels to meet the energy demand. The results of the model calculations for the baseline and alternative scenarios were presented. It has been shown that the optimal distribution of coal mining capacities promotes the import of the discussed fuel in the north-eastern part of the country and that the individual customer valuation leads to a decrease in the competitiveness of the units located in the central-western part of the country. The paper also discusses the potential impact of the domestic oversupply on the balance sheet and the price of coal. According to the obtained results and the basic laws of economics, an oversupply of coal leads to a decrease in prices. For the analyzed variants, the dependence of prices was estimated at PLN 0.0308 / GJ for every million tons of the oversupply. The fall in prices is largely due to the fuel supply to units located close to ports or railway border crossings. Based on the presented arguments it can be concluded that the maximization of financial result from the extraction of coal should be based on an analysis taking incremental changes in fuel prices into account.