The paper refines the study at the regional or industrial level to micro-enterprise level based on the Porter hypothesis and empirically analyzes the impact of environmental regulations on R&D effort of enterprises using zero-inflated models with application to Chinese thermal power listed companies. Firstly, environmental regulation intensity has a U-shaped relationship with Chinese thermal power plants’ R&D inputs. The relationship between environmental regulation intensity and R&D inputs is negatively regulated by enterprise scale. Enhancing the environmental regulation intensity can promote enterprises to increase R&D inputs. However, with the expansion of enterprise scale, the strengthening environmental regulation will reduce the R&D inputs. Secondly, environmental regulation intensity has an adverse U-shaped relationship with the number of patent applications of Chinese thermal power plants. The relationship between environmental regulation intensity and the number of patent applications is negatively regulated by enterprise scale. Therefore, if environmental regulation intensity is too high, the number of patent applications reduces. However, the problem will be eased and even reversed by the expansion of enterprise scale.