Most efficient way to aggregate data to new table
This is what SSAS was made for, and there are a whole host of client tools that can connect to it including Excel.

Elaborating

SSAS - SQL Server analysis services is a free component of SQL server, which will build a multidimensional version of your data(cube), that will pre-build all the aggregations you require/define.

The design tool is free to download called SQL Server Data Tools.

Once you set up the data source and data view based on the table you have the easiest way to go is to create a Dimension and Fact based on your table the dimension will have all the Metadata descriptors and the fact will just have the numerics/measures.

You then join the two in the Cube, once published/deployed both SSRS and other tools can connect to it.

Some links

https://www.codeproject.com/Articles/658912/Create-First-OLAP-Cube-in-SQL-Server-Analysis-Serv

https://technet.microsoft.com/en-us/library/ee677579.aspx