With oxygen enrichment in hot stoves (HS) the high calorific coke oven gas can be saved due to the possibility of using lower calorific gases which enables replacement of other imported fuels such as oil or LPG. The application of oxygen enrichment in hot stoves or increased O2 content in the blast to the blast furnace (BF), will also potentially lead to lower coke rate. The demand for coke oven gas depends on internal operation logistics and it also has outdoor temperature dependence through a heat and power plant producing district heat to the community. An analysis of the influence of increased oxygen enrichment in HS-BF on the entire energy system has been carried out by using an optimization model. A method of achieving a high time resolution in MILP optimisation is applied in the analysis. Different strategies have been suggested for minimum energy consumption at the studied steel plant and the nearby combined heat and power (CHP) plant. Central to the performance in system optimisation is the ability to analyse and properly describe the system variations.