Power BI consultant design scalable BI solutions by creating modular and reusable data models that accommodate growing data needs. They set up efficient data pipelines using dataflows and implement best practices for data storage and management. Consultants also configure incremental data refresh and optimize report performance to handle large datasets. They establish a governance framework that supports scaling, including standardized metrics and processes. This scalable approach ensures that as the organization grows, its Power BI environment can seamlessly handle increased data volume and complexity, providing consistent and reliable insights over time.