Same here, I’m using Home Assistant for a few years and now my energy provider allows me to download historic energy data as simple CSV files with , e.g.:
Date;Time;Data [kWh]
2021-09-04;00:15:00.000;0,152;
2021-09-04;00:30:00.000;0,150;
2021-09-04;00:45:00.000;0,150;
It would be great to import this historic data to make it available for use in the energy dashboard.