Redistribution of oxygen vacancies in a strontium titanate single crystal is caused by an external electric field. We present electrical measurements during and directly after electroformation, showing that intrinsic defect separation establishes a non-equilibrium state in the transition metal oxide accompanied by an electromotive force. A comprehensive thermodynamic deduction in terms of theoretical energy and entropy calculations indicate an exergonic electrochemical reaction after the electric field is switched off. Based on that driving force the experimental and theoretical proof of concept of an all-in-one rechargeable SrTiO3 single crystal energy storage is reported here.