This study theoretically investigates energy-saving investment incentives in duopolies. First, we investigate a binary choice model in which each firm chooses whether to make an energy-saving investment and then they face Cournot competition. We focus on the incentive to become the leading firm by the investment, when the rival does not engage in this project. We find the private incentive to be insufficient for welfare (thereby requiring promotion through policies), if Pigouvian tax is imposed. However, this incentive can be excessive when the emission tax rate is lower than the Pigouvian level. Next, we investigate a model in which firms can choose energy-saving investment levels continuously. We find that the equilibrium investment can be (is not) excessive for welfare when the emission tax rate is lower than (equal to) the Pigouvian. These results suggest that policy formation combining a low emission tax and subsidies for promoting energy-saving investments may harm welfare. Moreover, we find that drastic innovation rather than minor improvement of energy efficiency should be subsidized because the former less likely leads to Jevons paradox.

中文翻译：

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双头垄断市场中的最佳节能投资和 Jevons 悖论

本研究从理论上考察了双头垄断企业的节能投资激励措施。首先，我们研究了一种二元选择模型，在该模型中，每家公司选择是否进行节能投资，然后他们面临库尔诺竞争。我们专注于通过投资激励成为领先的公司，当竞争对手不参与这个项目时。我们发现，如果征收庇古税，私人激励不足以用于福利（因此需要通过政策进行推广）。然而，当排放税税率低于皮古夫水平时，这种激励措施可能过分。接下来，我们研究了一个模型，在该模型中，公司可以持续选择节能投资水平。我们发现，当排放税率低于（等于）皮古维安时，均衡投资对福利来说可能（不是）过度。这些结果表明，将低排放税和促进节能投资的补贴相结合的政策制定可能会损害福利。此外，我们发现应该补贴大幅创新而不是能源效率的微小改进，因为前者不太可能导致 Jevons 悖论。