Why does dataflow take up much more spaces than local pbix file?

[asherchen57]

Hello, 

I am a newbi to Power BI online and dataflow. I used power query to transform a table into a 300k rows data table, the final file is a 5MB file in the local drive. 

I copied and pasted the same code to Power query online through the data flow function. When I use Power BI desktop to extract data from this dataflow, I notice the same transformed data table become 200MB.  

I expect to have about 20 millions rows in next five years, I wonder if it is still fessible to use dataflow feature, why dataflow would take up 40 times larger for the identical data tables? 

Thank you. 

[Migasuke · Accepted solution]

I think you have the similar problem, which is discussed on one of the old post here:

https://community.powerbi.com/t5/Desktop/Why-does-Power-BI-quot-Load-quot-much-more-data-volume-than...

[asherchen57]

Thank you!

[Migasuke]

Hi @asherchen57 ,

do I understand correctly, that once you load your 300k rows using dataflows, your pbix had size of 200MB? (or 200MB was downloaded, but the pbix is much smaller?)

Anyway - I am using dataflow, which transforms around 15-20 Mil rows. If you do not use dataflow with some huge merging or grouping by - it will work smoothly.

[asherchen57]

I just tested it, the pbix files have similar data size in the local drive.

The problem is when I download/refresh the data from dataflow, it would take at least 10 mins to download for 10 million rows. The downloading screen also show it's downloading 7GB of data.

Do you have a window show the data is downloading once you hit refresh?