Hi,

I think the summary cells are exported as text intentionally, so as not to lose any literal text in the formatting. You don't have any literals in your DisplayFormat, but the default summaries do.

You could easily work around this by handling the SummaryCellExported event and writing the value and the format directly to the cell.

        private void ultraGridExcelExporter1_SummaryCellExported(object sender, Infragistics.Win.UltraWinGrid.ExcelExport.SummaryCellExportedEventArgs e)
        {
            Worksheet ws = e.CurrentWorksheet;
            WorksheetRow wsRow = ws.Rows[e.CurrentRowIndex];
            WorksheetCell wsCell = wsRow.Cells[e.CurrentColumnIndex];

            wsCell.Value = e.Summary.Value;
                        
            // Note that DotNet formats and Excel format are not the same. So you can't just
            // set the FormatString to e.Summary.SummarySettings.DisplayFormat. You have to             
            // translate it into a format Excel can understand. 
            wsCell.CellFormat.FormatString = "0.00";
        }