Steam methane reforming (SMR) process is the most important hydrogen source in SLOVNAFT refinery. Being a large natural gas consumer and important heat exporter, its operation mode and efficiency influences the whole refinery. In case its debottlenecking is to be considered, an adiabatic pre reformer installation can be considered among other options. In order to correctly calculate and analyze the corresponding benefit, the authors firstly dealt with the newer SMR plant design state verification and recalculation. It has been shown that taking into account the “approach to equilibrium” parameter is crucial to assess the underlying material and heat balances. Its design values are around 20 °C for radiation section and 8 to 10 °C for the high-temperature shift reactor which reflects the conservative approach of the plant vendor to process guarantees. Further process investigation is considered with the aim to set the plant operation efficiency properly into the wider scope of energetic media consumption of the whole refinery.