If you have installed a PPC smart meter gateway, you may also be able to retrieve the data via its HAN interface. Theoretically, the HAN port should even provide enough power that the reader can be operated autonomously. I am currently facing the same problem and am in exchange with a Norwegian store, whether their HAN reader is also suitable for German electricity meters with HAN port:
I also have a meter from Netze BW. If the thing with the HAN port does not work, I would try to write a custom integration for Netze BW and Home Assistant.
Even if the current aggregate levels of the measurement data on Netze BW are not so well suited for this in my opinion. :-/