In this scenario, the project manager should consider the delay as an opportunity due to the upcoming tax reduction on renewable energy products. By updating the risk register, the project manager can document this opportunity and plan how to leverage it, potentially reducing costs. This approach aligns with risk management practices that not only address threats but also identify and capitalize on opportunities that can benefit the project.

The guidance provided is in accordance with the principles of risk management outlined in the PMBOK® Guide, which includes the identification, analysis, and response planning for project risks and opportunities. Additionally, the PMI-PBA emphasizes the importance of stakeholder engagement and communication, which would be relevant in discussing and managing the changes with all stakeholders involved.