I would like to write out some data to classic XLS file.
I have installed MS Office 2013 in the developer PC.
In MS Visual Studio 2015 I see two versions of Microsoft.Office.Interop.Excel are 12 and 14.
And my question is what do I have to install on client PC so application is gonna work?
You don't install the PIAs. They should already be present on the machine (as part of the Office installation) and usually in the GAC in order to be loaded at runtime.