The smart grid plays a pivotal role in advancing sustainability and achieving the goals of the 2030 Agenda for Sustainable Development. By integrating advanced digital technologies smart grids improve the efficiency and reliability of electricity transmission, while supporting large-scale renewable energy integration. This paper analyzes the financial landscape of smart grid technologies through a comprehensive examination of Exchange-Traded Funds (ETFs) that invest in this sector. Using portfolio optimization techniques, including Monte Carlo simulation and efficient frontier analysis, the study evaluates the risk-return profiles and diversification benefits of smart grid ETFs compared to traditional diversified portfolios. The results show that smart grid ETFs like GRID exhibit annualized returns of approximately 20% with a volatility of around 25%, which is significantly higher than the returns of traditional energy sector ETFs like XLE, which show a return of 8% but with a higher volatility of around 35%. This study provides insights for investors and policymakers by demonstrating that smart grid ETFs offer a strategic opportunity to increase portfolio performance while aligning with sustainable investment objectives.