You’ve already made great progress in parsing the Excel file and generating separate payloads for water, gas, and electricity. The next step—restructuring the payload so each month's data is nested under a mar-24, jan-24-style key—is just a matter of reshaping how you're pushing the objects.

Instead of pushing individual payloads into three arrays, consider creating a single object where each key represents the month-year (extracted from the first column of each row) and holds nested data for water, gas, and electricity.

Here's a real-world implementation that walks through exactly how to parse the table structure you've described—handling multiple utility types, nested subfields, and organizing everything cleanly under month-year keys using JavaScript and xlsx: Parsing Excel rows to nested JSON in JavaScript

It also covers how to convert Excel's date serial values, gracefully handle empty cells, and avoid hardcoded column indices. Definitely worth checking if you want to make your import more robust and future-proof.