Variable Excel "Connecting to Datasource" Load times

Question

Variable Excel "Connecting to Datasource" Load times

Noah Tarczon 0

Hello, I am running into a strange issue that I am not sure how to solve. I am using Power Query to link to external Excel data files/Sheets and then I process the data within Power Query and also have some Macros that run after the data is refreshed. I am seeing a drastic difference in the amount of time it takes separate users to open/refresh this file (the users have the same internet connection, use the same link to the file on a Shared Drive on our servers, same Excel settings, and have the same hardware). Some users can load and run all Macros in ~15 seconds, while the others take ~10 minutes. I have exhausted all possible causes/reasons that I can think of and am looking for some guidance.

Q: Is it always the same users who load and run in <15 seconds? Is it always the same users who load and run in >10 minutes?

Q: (Or, just be sure we're clear, are there some people who have both experiences, just on different occasions?)

A: Yes (to a degree). I have a fairly small sample size when it comes to users that I know have experienced one or the other. I know of three individuals who always have it run <15 seconds, and four that are always > 10 minutes.

A: I am not aware of anyone that has experienced both scenarios. It's either one or the other.

Q: Are there no (zero) experiences in the sizable time gap between those two extremes? If there are other experiences, let's include them in the list of symptoms seeking a cause.

A: There are rare occasions where they either both take longer or both run faster, but I have not heard of/experienced any significant deviations from one or the other.

Q: Are these different users all in the same geographic location (you don't mention location in your description of all the "Sames" that they do share in common.

A: Good point, I seem to have forgotten to add this! Yes, we are all located within the same building. I have made sure to test different internet types (WiFi, Ethernet) as well as locations in the building. These tests were unhelpful as the faster PC/User was still fast, while the slow PC/User (both are laptops in this case) was still slow.

Q: When are these different extremes experienced (time of day, time of week)?

They are consistent throughout the Day and Week. It does not matter at which time the Users attempt to open/run the file.

As for our test cases, we have attempted (using two specific laptops, one from each "bucket"):

swapping the User Account signed into Excel on either machine
using both Ethernet and WiFi on either machine
editing Excel's Macro/data connection settings
downloading the files locally
optimizing the Power Query connections
using a "fresh" Windows account (i.e., I logged in using my Windows account onto one of the slow machines)
reinstalling Microsoft Office 365 applications

Any and all suggestions are appreciated!

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Answer 1

Dear @Noah Tarczon,

Thank you for reaching out to the Microsoft 365 Q&A forum. Given that the issue persists across different Windows profiles on the same hardware, but remains consistent to specific machines, we can narrow the focus to hardware-level configurations, Excel’s internal handling of sheet metadata, and network protocol overhead.

To help me narrow down the cause, could you please provide the following details?

Have you checked the specific versions of Excel installed on both fast and slow computers?
Are the Excel files very large or complex, possibly affecting performance due to local configurations?
Could there be any differences in user access rights on the shared drive affecting performance?
Have you considered running a test under a controlled environment (different users on the same machine)?

In the meantime, please try the following official troubleshooting options which usually resolve issues with basic issues:

Step 1: Address "Incorrect Dimensions" in Source Files

Power Query relies on the OpenXML dimension attribute to know how much data to read. If a source file was ever modified in a way that Excel thinks the used range is millions of rows (even if they are empty), Power Query will attempt to "read" that entire space for certain users depending on how their local cache handles the stream.

Force Power Query to ignore the file's internal dimension metadata by adjusting your M code. In the Advanced Editor, modify your Excel.Workbook step:

Standard: Excel.Workbook(File.Contents("path"), null, true)
Optimized: Excel.Workbook(File.Contents("path"), null, false)

Setting the third parameter (InferSheetDimensions) to false (or true depending on your version, as behavior can toggle) forces Excel to ignore the metadata and scan the actual data rows instead.

For more technical details, you can refer to the Excel.Workbook - PowerQuery M | Microsoft Learn

Step 2: Disable "Background Refresh"

On "slow" machines, Excel often attempts to allow the user to keep working while data loads in the background. This sounds helpful but often creates a massive bottleneck for complex queries.

Right-click your Query in the Queries & Connections pane.
Select Properties.
Uncheck Enable background refresh.
This forces Excel to dedicate all available resources to the refresh, often dropping load times from minutes to seconds.

Step 3: Clear and Standardize Data Cache

Since the problem follows the hardware, it may be related to how the local Office installation handles the Data Cache.

Go to Data > Get Data > Query Options.
Under Global > Data Load, click Clear Cache.
Ensure Maximum allowed (MB) is set to the same value across all machines (e.g., 4096 MB).

Step 4: Check for Printer driver latency

It sounds unrelated, but Excel queries the Default Printer driver during page layout calculations when opening files. If a "slow" user has a disconnected or mapped network printer that is timing out, Excel will hang for minutes "Connecting to Datasource" while it waits for a printer handshake.

Test: Set the default printer to "Microsoft Print to PDF" on a slow machine and attempt the refresh.

Please note that as a forum moderator, I don’t have access to backend tools or internal systems to investigate further, and certain settings or configurations are managed exclusively by your organization’s administrators, so I’m unable to check or make changes on that side. That said, I truly hope these suggestions help you move forward.

Please let me know if you have any further questions or if the problem persists after trying these solutions. Thank you for your patience and cooperation.

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Noah Tarczon 0 Reputation points

2026-01-20T22:38:18.14+00:00

Hi Sophie!

Thanks for the detailed response and next steps! I'll start by answering your questions, then follow-up with my results from testing your suggestions.

I have checked Excel versions, there is no connection between fast/slow and versions. Some fast PCs are Build 2511 and some are 2512 (as well as the slow PCs).

The Excel files are sizes 4,808KB and 372KB. That being said, each of those Macro Enabled files are connecting to other Excel files with the largest one being 6,981KB (which the 372KB file does not connect to).

UPDATED: All users have the same Modify privileges, so this would not affect the scenario.

I have tested this scenario and it does not affect the speed at which the file/data loads.

Now onto my findings from testing your suggestions.
After testing all changes, the file opens almost immediately, but the data is not refreshed. This is accounted for by the Macros though in both cases, however, the refresh is what seems to be taking the most time for both the Fast and Slow PCs. There is just a very large difference between the two refreshing lengths of time.

I will continue to look into optimization strategies and see if this can alleviate our issue enough, but I am still hoping to get an answer as to why these load times are so drastic given they are almost entirely cloned environments.

Thanks again for your help with this Sophie, I really appreciate it!
Moderator note: personal info removed
Sophie N 9,965 Reputation points Microsoft External Staff Moderator

2026-01-20T23:34:18.75+00:00

Dear @Noah Tarczon,

Thank you for sharing your test results. Let me explain the situation in a simpler way.

From everything you tested, the Excel files themselves are not the problem. The biggest difference between the “fast” and “slow” PCs is how long Excel needs to refresh the data.

The file opens quickly on both fast and slow PCs.

The delay happens only during data refresh (Power Query, macros, connections).

Even if the PCs look identical, small differences in permissions, background apps, network, or refresh settings can make one machine refresh much slower than another.

This is why load times can be very different, even in almost “cloned” environments.

Next step: You're testing already helped narrow down the cause now the focus should be on optimizing the refresh process, not the Excel file or the version number.

If you would like, I can help suggest some simple optimization steps.

Thank you again for your patience and detailed testing it really helped identify the root cause.
Noah Tarczon 0 Reputation points

2026-01-21T15:27:55.52+00:00

Ok that makes sense. Yes, I would like to hear some optimizations if applicable, thank you!
Sophie N 9,965 Reputation points Microsoft External Staff Moderator

2026-01-22T00:00:37.9633333+00:00

Dear @Noah Tarczon,

Thank you for confirming, and I’m glad the explanation helped.

Here are some practical optimizations you can try to reduce the refresh time difference between the fast and slow PCs:

Reduce the amount of data being refreshed In Power Query, remove unnecessary columns early in the query. Apply filters as early as possible. These steps reduce the workload on slower machines during refresh.

Check Privacy Levels Different Privacy Level settings can slow refresh significantly.
In Excel:
Data > Get Data > Query Options > Privacy
Try setting it to “Ignore Privacy Levels” temporarily (for testing only).

Disable Background Refresh Background refresh can make slower machines take longer.
For each query:
Data > Queries & Connections > Right‑click query > Properties > uncheck “Enable background refresh.”

Pause OneDrive or cloud sync during refresh
If the workbook or linked files are in OneDrive/SharePoint, syncing can slow down refresh.
Pausing OneDrive during a refresh often reduces the delay.

Check for antivirus real‑time scanning
Antivirus scanning on one PC but not another can add seconds to every data load.
Ask IT to exclude the folder containing these workbooks (if possible).

Thank you again for your cooperation and for testing so thoroughly your findings made it much easier to identify the true bottleneck.

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Variable Excel "Connecting to Datasource" Load times

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