The energy efficiency of the Polyethylene oxide (PEO)/soy protein isolated (SPI) membrane was studied. The different PEO/SPI ratios (10wt% SPI, 30wt% SPI, and 50wt% SPI) are successfully made by denaturing the SPI at a high temperature (60°C) to compare with the pure PEO membrane in case of energy efficiency. Moreover, the effect of the polyethylene oxide molecular weight was studied by using two different molecular weights (1,000,000 and 100,000g/mol.). The Current-Voltage and Hysteresis tests were measured to study the electrical behavior of membranes. Additionally, an LCR meter was used to measure the capacitance of the membranes. We conclude that the presence of the SPI in PEO/SPI membranes contributes to a dramatic increase and there is an optimum amount for the PEO/SPI ratio. In addition, the PEO low molecular weight has better performance than high molecular weight PEO. Likely this is due to a better interaction between polymeric chains and protein molecules in lower molecular weight PEO. Keywords: Energy efficiency; Polyethylene oxide (PEO); Soy protein isolated (SPI); Denaturation; Hysteresis