Power BI vs Data Warehouse

Power BI/Qlik/Tableau VS Data Warehouse is probably the biggest misconception in the Business Intelligence space. Every few months, a new senior manager will ask this exact question. Let's save a million $$$ a year and stick with Power BI.

We shoud, in fact, be comparing 'Power BI/Qlik/Tableau to SSRS' as all of these products are for designing reports.

As someone else here said, a data warehouse and Power BI complement each other. You mentioned SSAS. Power BI/Qliksense/Tableau are pretty useless on their own in a large organisation. They do not have the capacity to interrogate, load and report on big data.

Instead of a data warehouse, perhaps a data mart may suffice for many, which will be a few databases that work specifically for reporting, but not necessarily have the same firepower as a data warehouse.

Here's the truth... once you give someone a taste of reporting, they will only want more and more as time goes on. Requirements will get more complex. Eventually, a data warehouse will be necessary anyway.