Two thoughts:
- If you are handy with Python and don’t mind storing your own data, you can use the informal API. @MarkDodrill posted a sample here a few days ago.
- If you want a data collection platform that you can used to overlay graphs, consider using Home Assistant. It has a built-in integration using the Sense informal API, plus allows you to use InFluxDB and Grafana add-ins to graph the collected data.
Sense - Home Assistant