Abstract Microemulsions (µEs) have been proposed as redox flow battery (RFB) electrolytes that maximize ionic conductivity and charge capacity by synergizing two immiscible phases. However, charge transfer during electrolysis in µEs is poorly understood. Here, we show that ultramicroelectrode electrolysis of ferrocene-loaded µEs - 20%, 60%, and 90% water - reveals stochastic current fluctuations. These are differentiated in the scanning electrochemical microscopy (SECM) geometry, where power spectral density analysis showed distinct changes in the frequency contributions. SECM in the substrate generation-tip collection mode showed that fluctuations arise under mass-transfer control. Significant differences in the diffusion coefficient of ferrocene species were deducted from SECM approach curves, suggesting phase transfer behavior. Using bulk electrolysis, we calculated the charge accessibility and cycling behavior in the µEs. A decrease in the stochastic behavior of the µEs seems to correlate to a higher accessibility and cycling performance, with the 90% water µE displaying the best reversibility and the 60% the lowest. Altogether, these results suggest that Marangoni-type convection driven by concentration gradients and/or µE restructuring during charge transfer play a role in the electrochemical performance of µEs. This presents opportunities for screening and diagnosing the performance of these emerging RFB electrolytes.