Power BI consulting measure project success by evaluating whether the delivered reports, dashboards, and data models meet the business objectives and provide actionable insights. They also assess the performance, usability, and adoption of Power BI tools across the organization. Success is gauged through key performance indicators (KPIs) such as improved decision-making speed, increased user engagement with reports, and the ability to derive insights in real-time. Feedback from stakeholders, scalability of the solution, and the overall efficiency of the data processes are also considered in determining project success.