This paper reports on the performance of the supercapacitor operating in aqueous acetic acid salts. Lithium, sodium and magnesium acetate aqueous solutions at various concentrations have been selected as electrolytes. Maximum operational voltage and the overall capacitor performance have been determined by several electrochemical techniques. Floating and galvanostatic charge/discharge tests proved the promising performance at high voltages (1.5V); the capacitance values have been retained at more than 80% of initial value for all tested electrolytes. Additionally, due to the the ability to operate at high voltages, the maximum energy obtained in the system with 0.5molL−1 CH3COONa is more than two times higher than with 6molL−1 KOH, i.e., conventional aqueous capacitor. Taking into account a mild character of the electrolytes used, a novel concept of eco-friendly energy storage device has been proposed.