Hi,

We have a report with 300+ columns and there are 3000 records. The report takes over 15 minutes to render into Excel. (We are not talking about time from server to browser here). This is on local machine.

Anyone has idea is whether this slowness is due to high number of columns? We checked the SP that it returns the data very fast. 

Thanks
Piyush Bhatt

Hi Piyush,

Number of report items and number of returned data rows from the data source definitely affects the load time of the report. It doesn't matter that the data is retrieved for less time from your database, it still needs to be processed by the reporting engine.
You can optimize your report layout and the data you display by following the suggestions in Performance Considerations - http://www.telerik.com/help/reporting/designing-performance.html
Also Excel has some specifics and in order to export to Excel faster, you need to perfectly align all of your report items (e.g. by using a Table) so it does not generate extra columns/rows. Please check Excel Rendering article - http://www.telerik.com/help/reporting/designing-reports-considerations-excel.html