Fabric Chargeback Reporting

There is no out-of-the-box alert in the Fabric Chargeback app to automatically notify which user, item, or workspace consumed the most CUs.

What you can do today:

• The Fabric Chargeback app (preview) delivers visuals showing CU usage by workspace, item, and domain/subdomain, and offers a matrix with user breakdown, hovering reveals per user CU contributions
• You can filter, drill into workspace/item visuals, and export the report data (ex: to CSV/Excel) then manually analyze it to identify top consumers
• The app’s data refreshes once daily and isn’t real-time though manual refresh is possible

But, alerting? That’s handled via Data Activator:

• With the Fabric Capacity Metrics app plus Data Activator, you can set up alerts based on thresholds in CU usage, for ex: if CU consumption exceeds a certain limit
• You’d have to custom-build the logic, for instance: “Alert me when User X’s CU exceeds Y” or “Workspace/Item CU top X%”, you define the threshold and trigger.

My recommendation:

Since you're looking for “who consumed the most CUs,” go with a custom solution using the Metrics App’s semantic model, store the data in OneLake, and apply either Power Automate or Data Activator rules to generate alerts. 

Please Kudos and 'Accept' as solution if the reply was helpful. This will be benefitting other community members who face the same issue.