A penny saved is a penny earned: Exploring the synergistic effect between carbon trading and energy carbon-content tax

Currently, numerous studies are being conducted on various carbon reduction policies, but their synergies have been poorly investigated. This paper examines the synergistic effect of combining emissions trading schemes (ETS) and energy carbon-content taxes (ECT), using China as a case study. A computable general equilibrium model is used to identify the synergistic effect of these two carbon mitigation policies. The results show that the synergistic effect helps to reduce GDP loss by approximately 5.44 billion CNY, which accounts for 2.83% of the overall GDP losses caused by ETS and ECT. Additionally, the synergistic effect reduces an additional 5.25 million tons of CO2 emissions and decreases the negative impact on social welfare resulting from the two policies. Although these achievements are commendable, there are costs associated with this synergy. The effect on energy security presents mixed results and leads to increased carbon leakage. Therefore, policymakers should take heed of the potential "cocktail effects" that may arise in their pursuit of carbon neutrality.