Medium severityschema
Power BI Refresh Error:
Column type conversion failed during refresh
What does this error mean?
A value retrieved from the data source could not be converted to the data type expected by the Power BI model. This typically happens when source data changes in a way that breaks type assumptions.
Common causes
- 1A column that was purely numeric now contains text values (e.g., 'N/A', 'NULL', or empty strings)
- 2A date column contains values in an unexpected format that cannot be parsed
- 3A decimal column contains values exceeding the precision defined in the Power BI model
- 4The source changed a column from one type to another (e.g., INT to VARCHAR) without updating the dataset
- 5Locale-specific number formats (comma vs. period as decimal separator) causing parse failures
How to fix it
- 1Identify the specific column causing the error from the error detail — it usually names the column and value.
- 2In Power Query Editor, add a step to handle nulls and errors: use Table.ReplaceErrorValues or try...otherwise.
- 3Explicitly cast the column to the correct type in Power Query and handle edge cases (nulls, empty strings, 'N/A').
- 4If the source schema legitimately changed, update the column type in the Power BI model to match.
- 5For date parsing issues, use Date.FromText() with an explicit format string rather than relying on locale inference.