Today I was conducting an efficiency optimization session for Risk Management team of a global bank. During the discussion, one of the problems we discussed was large Excel files. Although there are many reasons for large Excel files, one of the reasons is easier to manage and it is largely unknown. It relates to files containing one or more Pivot Tables.
Pivot Table creates a copy of the source data and saves it in the file. This increases the file size and also slows down the open / close operations. You can ask Excel NOT to save the copy of the data and save on file size. Right click inside pivot, Pivot Table options, Data tab, clear the checkbox Save source data with file. That solves the file size inflation problem.
Read more to understand when to use and when NOT to use this feature.