Recently I was building a new SharePoint 2016 farm and came across the below error with older PowerShell SharePoint 2013 install scripts. Expected error as Microsoft moved the functionality to Office Online Server. Cheers!

Error Message
- The term ‘New-SPExcelServiceApplication’ is not recognized as the name of a cmdlet, function, script file, or operable program. Check the spelling of the name, or if a path was included, verify that the path is correct and try again.
Root Cause
- Microsoft removed the Excel Service Application from SharePoint Server.
- Office Online Server has the functionality going forward.
- https://technet.microsoft.com/en-us/library/mt346112(v=office.16).aspx