This work investigates the integration of nanofluids in a Carnot battery (thermal energy storage system) composed of an organic Rankine cycle and a vapor-compression heat pump. The study aims to evaluate the potential of advanced working fluids to enhance both thermodynamic and economic performance. An exergy and exergoeconomic analysis is carried out to assess the effect of nanofluids as working fluids on system performance. The study considers R245fa as a base fluid, both in its pure form and through the addition of Al₂O₃ and Cu nanoparticles, in order to improve heat transfer properties and system effectiveness. A comprehensive parametric analysis is performed to examine the influence of key operating parameters, including turbine inlet pressure, storage temperature, and compressor outlet temperature. The results indicate noticeable improvements in both thermodynamic performance and cost characteristics, highlighting the potential of nanoparticle-enhanced fluids to enhance the overall performance of Carnot battery systems.