Environmental　regulations　can　effectively　mitigate　environmental　degradation,　yet　their　impact　on　energy　efficiency　remains　unclear.　This　study　contributes　to　the　existing　literature　by　examining　how　the　Environmental　Protection　Tax　Law　(EPTL)　drives　energy　efficiency　and　demonstrating　its　environmental　and　economic　dividends.　Empirical　evidence　from　a　dataset　of　271　Chinese　prefecture-level　cities　from　2011　to　2020　reveals　that　EPTL　significantly　enhances　energy　efficiency　by　3.8%,　and　it　has　a　positive　spatial　spillover　effect.　The　underlying　mechanisms　are　improvements　in　environmental　governance　and　economic　development.　Heterogeneity　analysis　highlights　a　particularly　prominent　positive　impact　in　the　eastern　and　western　regions.　Our　study　confirms　the　effectiveness　of　EPTL　in　promoting　energy　efficiency　and　supports　the　double　dividend　hypothesis,　providing　policymakers　with　insights　for　formulating　differentiated　policies.