Does China’s Carbon Market Pilot Spillover? Spatial Effects on Power Sector Energy Efficiency Using an SDID Approach

As improving power sector energy efficiency is crucial for China’s sustainable low-carbon transition, this study investigates the impact and spatial spillover effects of carbon market pilot policies. Utilizing panel data from 30 Chinese provinces spanning 2009 to 2022, we employ a super-efficiency Slack-Based Measure (SBM) model alongside a Spatial Difference-in-Differences (SDID) approach to assess policy outcomes. Empirical findings reveal that while the pilot policy significantly improves local power energy efficiency by an average of 10.68%, it exerts a negative spatial spillover on neighboring regions (rho = −0.3802). This disparity occurs because asymmetric resource agglomeration causes the policy-driven “polarization effect” to dominate the “trickle-down effect”. Furthermore, mechanism analyses demonstrate that increasing the clean energy share—primarily driven by technological substitution, fiscal subsidies, and policy guidance—serves as the main transmission channel. However, strict short-term compliance costs induce a “strategic innovation” response, which promotes green utility model patents but crowds out substantive green inventions. Ultimately, this study highlights the necessity of establishing cross-regional carbon market alliances and technology diffusion mechanisms to mitigate regional disparities and foster collaborative carbon reduction, and promote long-term sustainability.