Save date depended data regardless of shut downs

I'm pretty new to Node-Red.
I'm using a revolution pi and a janitza umg 605 to read energy consumption data of a coffeemaker.
The revelution pi is not running permanently but is shut down, when the coffeemaker is not in use. This could be several times a day.

I need to find a way to get the total energy consumption data between 00:00:00 and 23:59:59 regardless of shutdowns and store it to a folder with the name of the respective date so i can read out the total energyconsumption of single previous days and compare it.

I get a value of the energy consumption every second and i know how to store context data to my file system. I already created a flow variable witch is stored to my file system every 30 seconds overwriting the previous value.

So what i need is:

  • a way to get the current value right before the pi is shut down and store it to another file
  • a function, that knows wich date it is and adds all stored "right before shotdown"-values for one day and store it to a file with the name of the date

I hope my question is kind of understandable.
Thank you for ideas.


Why not use a database to store the data (and a timestamp)?
Plotting graphs & barcharts would then be so much easier.

Indeed, InfluxDB is excellent at doing time-based storage and processing.

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