Based on the Coase property right theorem [
18], the energy rights trading policy defines the rights and interests of energy use and uses the market to achieve the Pareto optimal state of the energy allocation efficiency of the enterprise body, in order to achieve energy conservation and emission reduction at the lowest cost and improve environmental performance [
19]. During the policy implementation process, enterprises will prioritize improving technological innovation and reducing energy intensity in order to gain advantages in energy use right trading and obtain maximum benefits at the lowest possible cost. However, pollution control expenditure and investment in new technology research and the development of enterprises will inevitably increase the financing demand, and the level of marketization development will directly affect the difficulty of enterprises to obtain financing. Therefore, this study selects marketization development level and technological innovation as mediating variables to explore the impact mechanism of energy and rights trading on environmental performance.
2.1. Mechanism Analysis
Energy trading policies can improve the level of marketization and affect urban environmental performance. Since energy use rights policy shares enter the market as a “commodity”, its operation process will be affected by the insufficiency of market mechanisms, such as speculation, the lag between supply and demand, and other problems, thus the level of marketization is closely related to the implementation effect of energy use rights trading. First, imperfect competition is prevalent in the market for energy use rights in practice. Some enterprises take advantage of purchasing and storing rights, obviously exceeding their quota to seek profits or for future use [
20]. Whether the trading of energy use rights can be carried out in an open, fair, and reasonable trading market smoothly depends on the market level, the relationship between market and government, the development of the factor market, and so on. The total level of marketization reflects the degree to which factors flow from low-efficiency to high-efficiency sectors, and there is a positive relationship between the level of marketization and enterprise productivity. Second, in the practice of energy use rights trading, some local governments have “excessive intervention” in enterprises within the domain due to the consideration of economic development, which directly affects the enthusiasm of quota trading among enterprises. This indicates that the government is the key to effectively coordinating with the market to establish and perfect the market mechanism of energy use right trading. Only by relying on moderate government intervention and continuous marketization can we better promote the implementation of energy use right trading policy, which is required to improve environmental performance. Thus, this paper proposes Hypotheses 1:
Hypothesis 1. Energy use rights trading policy can improve the level of marketization development and have a positive effect on urban environmental performance.
Energy trading can stimulate the innovative vitality of enterprises. Combined with Porter’s hypothesis and the enterprise profit maximization theory, the energy trading policy has a promoting effect on enterprise technological innovation. The specific effects are mainly reflected in the following two aspects: First, innovation is the fundamental way for enterprises to pursue profit maximization. The trading use right policy of energy restrains the energy consumption of enterprises and stimulates enterprises to reduce production costs. Technological innovation has the potential to improve enterprise energy efficiency while also indirectly improving environmental performance. Second, the “Porter hypothesis” holds that moderate environmental regulation can bring compensation to enterprises for innovation activities and stimulate enterprises to carry out technological innovation activities [
21]. When the company’s energy consumption falls below the quota, the rich energy rights can be sold for profit and compensation for innovation. Furthermore, the government can benefit from the sale of energy use rights and invest in related energy conservation and emission reduction projects, which not only lowers enterprises’ expectations of innovation risks, but also improves environmental performance. Ideally, the implementation of energy use rights trading policy can stimulate the vitality of technological innovation of enterprises. Because it can promote enterprises to improve production technology for the purpose of reducing energy consumption, eliminate backward production capacity, and indirectly promote the improvement of environmental performance level. According to the above analysis, this study proposes Hypothesis 2.
Hypothesis 2. Energy use rights trading policy can improve the level of technological innovation and have a positive impact on environmental performance.
The difference in energy-saving potential will lead to different impacts of energy use rights trading policies in different pilot areas. As a result of the disparities in urban resource allocation, the improvement effect of energy use rights trading policies on environmental performance may be heterogeneous.
First, the size of the city will affect the implementation effect of the energy use rights trading policy. Large cities can produce the aggregation effect of factors, which is mainly reflected in the spillover of labor, capital, knowledge, and the decline of marginal production costs. The high concentration degree of the city and the advantages of high production specialization, and strong scientific and technological innovation ability brought by the agglomeration of manufacturers form the scale economy effect makes it easier to attract the inflow of foreign capital and human capital for technological innovation and marketization development. At the same time, excessive agglomeration will also lead to excessive resource development, energy consumption, and affect the improvement of environmental performance. Therefore, in cities of different sizes, whether the energy use rights trading policy can have the effect of energy conservation and emission reduction needs to be further investigated.
Second, urban resource richness will affect the implementation effect of the energy use rights policy. According to the notice on the Issuance of the National Sustainable Development Plan for Resource-based Cities (2013–2020) issued by The State Council [
22], resource-based cities can be divided into four categories: growth, maturity, decline, and regeneration, and there is a nonlinear relationship between resource abundance and ecological efficiency [
23]. Cities with insufficient resource endowments (recession) have the greatest motivation for transformational development and technological innovation. Therefore, the energy use rights trading policy has high impact. While abundant resources (growth) cities may rely too heavily on the low-end of resource-intensive industries, this can stifle technological progress and, to some extent, improve environmental performance. Therefore, the energy use rights trading policy may have a greater effect on the improvement of environmental performance in cities with declining resources, although its effect is not significant in cities with growing resources.
Third, different industrial structures will also lead to the heterogeneous impact of energy use rights trading policies on environmental performance. The old industrial cities rely too much on resource-intensive industries and suffer from extensive development patterns. In this way, the long-term overexpansion of the industrial sector led to capital accumulation, but also led to high energy consumption, high pollution, and stagnant production technology. Cities that are not old industrial bases have a reasonable industrial structure layout, a low reliance on energy consumption for economic development, and a high level of environmental performance. Therefore, the energy use rights trading policy has more space to grow in the old industrial base cities. Based on the discussion above, we propose Hypotheses 3:
Hypothesis 3. In cities with higher average urban economic income, resource decline, and higher industrial structure, energy use rights trading policy can perform a greater role.