A conducting redox polymer (CPR) based on pyrrole with a hydroquinone pendant group was synthesized through electropolymerization of the corresponding monomer. The formal potential (E 0′) in aqueous solution at different pH as well as in MeCN containing equal amounts of pyridinium-triflates and the corresponding free pyridine with different pK a was investigated. E 0′ could be completely recovered in MeCN, and by utilizing pyridine bases with different donor–acceptor strengths, a decrease of 61 meV/pK a was found that corresponded exactly to the pH dependence of E 0′ in aqueous electrolyte. To separate the entropic and enthalpic contributions to E 0′, temperature-dependent electrochemistry was performed. Two different modes of operation with changing pH/pK a between the two media were revealed. In MeCN, E 0′ varies only because of the enthalpic contribution as the entropic contribution is unaffected by change in pK a. In water, there is primarily an entropic contribution to E 0′ with changing pH due to solvation of the proton. The presented results are expected to open up for new design possibilities of CRPs based on ion-coordinating redox groups for electrical energy storage.