Speed Up Excel Power Query Get Data Refreshes for Large Files
Question details
The user wants to reduce refresh time for Excel Get Data and Power Query queries that use large source files.
- Product
- Microsoft Excel Power Query and Get Data
- Device & OS
- not provided
- Scenario
- Refreshing a query that imports data from a large CSV file or another large data source.
- Observed behavior
- The query refresh takes a long time because it reads and processes more records, columns, previews, or transformations than necessary.
Identify the source type and determine whether it can return only the required date range, records, or columns. In Power Query Editor, review Applied Steps to find transformations that process the full dataset before filtering.
Filter rows and remove unused columns at the start of the query
Use this as the primary optimization for large files and data sources. Reducing the dataset before other transformations usually provides the largest refresh-time improvement.
Power Query reads the source data but does not delete or modify records in the original file. Apply filters and column removal as close to the Source step as possible so later steps process less data.
When a CSV receives new records at the bottom, use Keep Bottom Rows directly instead of reversing the entire table and then keeping top rows.
In Excel, select Data > Queries & Connections, right-click the query, and choose Edit.
Select the relevant column, such as a date or status column, open its filter arrow, and choose only the values or date range needed. Keep this filter near the Source step in the Applied Steps pane.
Select the columns needed for the final result, then choose Home > Remove Columns > Remove Other Columns.
If new CSV records are appended at the bottom, choose Home > Keep Rows > Keep Bottom Rows and enter the number of rows required.
Select Home > Close & Load, then use Data > Refresh All to test the improved refresh time.
Move data-type conversion steps after filtering
Use this when the query changes data types before it reduces the number of rows or columns.
Adjust Power Query preview, load, and privacy options
Use this when large previews, loading behavior, or privacy-level checks add overhead after the query itself has been streamlined.
Work with Large CSV and Excel Data in WPS Office Spreadsheets
If Excel Power Query refresh performance is affecting your workflow, WPS Office provides a free, lightweight spreadsheet alternative for opening, organizing, filtering, and analyzing large workbook and CSV data with a familiar Office-style interface. You can move existing files into WPS Office with minimal adjustment for everyday spreadsheet work.
Frequently Asked Questions
Does Power Query delete records from the original CSV or database?
No. Power Query reads and transforms a copy of the source data for the query result. Filters, removed columns, and Keep Rows operations do not delete records from the original source file.
Why should I remove columns before changing data types in Power Query?
Removing unnecessary columns first reduces the number of values Power Query must process. Apply Home > Remove Columns or Remove Other Columns before using Transform > Data Type when possible.
How do I keep the newest records from the bottom of a CSV file?
Open the query in Power Query Editor, then select Home > Keep Rows > Keep Bottom Rows. This avoids reversing the full table merely to keep rows that are already at the bottom.
What is the fastest way to improve a slow Power Query refresh?
Limit the data returned by the source whenever possible, such as with a date-range filter in the database, API, or source system. Then keep filters and column-removal steps immediately after the Source step.
Should I disable Power Query privacy settings to make refreshes faster?
Only change privacy behavior when it is appropriate for your data sources and organizational requirements. First optimize the query by filtering early and reducing columns, then review File > Options > Data > Query Options > Privacy if refresh checks remain a concern.
