Power BI developers enhance reporting efficiency by automating data refreshes, streamlining data processes, and creating reusable templates. They design dashboards that provide real-time insights, reducing the need for manual data processing and report generation. By optimizing data models and implementing efficient DAX formulas, they ensure reports load quickly and run smoothly, even with large datasets. This efficiency allows stakeholders to access up-to-date information whenever needed, improving decision-making speed and reducing the time spent on manual reporting tasks.