Power generation of Estonia is based on oil shale today. The share of oil shale in power generation is over 90 per cent. According to prognoses of Estonian economic growth, the need for energy will grow and even if apply­ing alternative power sources, it cannot be realistic that it could be reduced to less than 50 per cent of today’s volumes in 2020. Because of the increasing cost of crude oil, oil generation from shale is of growing importance. But oil shale is very rich in ash, which results in huge amounts of solid residues. In addition Estonian oil shale has a great content of carbonate minerals thus combusting and oil processing is accompanied by abnormally high emissions of CO_2. Though emission of sulphur dioxide is low due to carbonate minerals, limitation of SO₂ pollution is expected in the near future. In relation to growing environmental requirements, the interest towards utilisation of oil shale of higher calorific value has grown. As it is clear that higher calorific value of product causes higher production expenditures, the question arises where is the optimal point. Consumers are interested in a fuel raw material of higher quality. Upgrading of oil shale results in higher operating expenses and requires also applying of a new price scale. Optimizing the grade of the oil shale as well as the quality of the shale oil to best fit the interests of the mines and consumers is the subject of this paper.