The ongoing transformation of the Italian electricity system is reshaping both the generation mix and the wholesale market architecture, with increasing relevance attributed to zonal price formation. In this context, Sardinia represents a paradigmatic case, being an island power system historically dependent on imports and characterized by strong sensitivity to local supply–demand conditions. The phase‑out of the Single National Price (PUN), the strengthening of interconnections with the mainland, and the development of the island transmission grid are expected to lead to a framework in which electricity prices for both producers and consumers will fully reflect local system conditions.

Within this evolving scenario, the level of Renewable Energy Source (RES) deployment emerges as a relevant driver of price dynamics. A significant expansion of solar and wind capacity, potentially exceeding local electricity consumption during specific hours, can reduce reliance on imported energy and residual thermoelectric generation, thereby lowering the Sardinian zonal price and mitigating exposure to national commodity volatility.

This paper presents the results of day‑ahead market simulations conducted for 2030 using a zonal representation of the Italian electricity system. Multiple scenarios are analyzed, sharing the same infrastructural configuration and market rules but differing exclusively in the level of RES integration on the island. The simulations assess the impact of alternative renewable development trajectories on zonal price formation, exchange flows with other market zones, and aggregate welfare indicators such as social welfare and the total value of transactions.

The results show that infrastructure development and market evolution, while necessary to enhance system integration and security, are not sufficient to ensure long‑term price competitiveness for Sardinia. Instead, the scale of local renewable capacity proves to be the decisive factor in determining the island’s economic positioning within the national electricity market. The paper finally discusses the implications for coordinated network–generation planning, highlighting infrastructure investments as enabling conditions for a sustainable, competitive, and resilient energy transition in the island power systems.