Electrochemical systems, including Hall-Héroult cells, are studied using equivalent circuit models to analyse their electrochemical response. These models typically consist of resistive and capacitive elements representing electrolyteElectrolyte resistance, charge transfer resistance, diffusion processes, and double-layer capacitance. Electric circuit modelling requires manual inputs, including the selection of appropriate circuit configurations and the iterative fitting of different models. Transfer functionsTransfer function offer an alternative by mathematically describing how dynamic systems respond to inputs in the frequency domain and are commonly used in control theory and signal processingProcessing to assess system stability and response. This modelling approach can reduce subjective decisions in representing electrochemical cells. Despite its potential, the application of transfer functionsTransfer function to the modelling of electrochemical systems has not been extensively explored. This study applies system identification techniques to extract transfer functionsTransfer function from an experimental acidic water electrolyser with varying electrolyte compositionsElectrolyte composition, revealing both the challenges and opportunities for monitoring electrolysisElectrolysis systems with this technique.