Model for payback time of using retired electric vehicle batteries in residential energy storage systems

This work presents a mathematical model for the payback time of reusing electric vehicle batteries as residential energy storage systems from the end of life of automotive application. The model was developed using MATLAB software and calculates the payback time of a battery energy storage system (BESS) under different scenarios while considering the daily electricity consumption profile for a UK household. The results show that battery purchase price, BESS capacity, electricity unit rates and electricity demand profile are variables with large effects on the payback time. At the simulated baseline condition with residential households of two people, a BESS using second-life batteries from five different vehicle models showed payback time ranging from 8.3 to 12.8 years. The combination of battery rightsizing to attend peak and standard demand, battery price drop by 46%, reaching the level where EV price becomes competitive with conventional vehicles, and BESS application to three or more households provides the most favourable scenario with the minimum payback time of 4.8 years. Further reduction in the payback time of up to 41% can be achieved with subsidised off-peak electricity unit rate.