Taking huge time to data refresh in Power Query Editor

[aAmirkHan]

Hi Power BI Expert,
I am fetching data from two Excel files having sizes 150 MB and 180MB into Power Query of Power BI.
When I perform Data cleaning tasks in Power Query Editor then it takes a lot of time to refresh the data in Power Query Editor.

Two Excel files are saved on my computer drive.

Moreover, I am using a Dell laptop having 16 GB RAM for the Power Query task.

Can you please suggest to me what should I do to improve the data refreshing performance?

Thank you 

@amitchandak @Pragati11

[mussaenda]

Hi @aAmirkHan ,

It depends on your applied steps. 

Are you having extensive steps?

[aAmirkHan]

Hi @mussaenda 
Since I was not feeling good, I am Sorry for being in delay your response. Below are the steps that I followed up in Power Query of Power BI.

There are two Excel files 1st is 150 MB and 2nd is 180 MB.

Steps 

1. I fetched two Excel files in Power Query.

2. I applied the Append command to combine files rows-wise.

3. I applied the correct data type for each column.

4. I did a data normalization process, before doing it I replaced null and blank value in each column with the "NA" value.

5. I matched the correct keyId in the data modeling part.

Above are the steps that I used in the ETL process in Power Query. However, it is still taking a lot of time to refresh data in a preview of Power Query.

Can you please advise me, on how can I fix it?

Thank you