Power BI is a series of free add-ins for Excel starting in 2010. Depending on your year and version they are either included or are downloadable. They are available in the standalone products and Pro Plus. Additionally there is a standalone, free program Power BI Desktop Pro which includes all the pieces without a dependency on Excel at all.

The desktop and mobile apps are completely free and the desktop pieces can be used without a server. The web portal is cloud-hosted and freemium to anyone with a corporate email address and the mobile apps require at least the free web portal.

Feel free to email me if you're curious about more details. Gregory.Baldini at gmail dot com.