P1000

Hmmm. Perhaps you'll have the best luck listening in on the communications between the Wifi module and the inverter.

I'd be very surprised if the data is actually raw and unencrypted.

This might be a start: https://github.com/jantenhove/GoodWeLogger It connects to the inverter over RS485 (Modbus RTU IIRC). It might also not be applicable to your inverter model, but maybe it is a start?

Compared with other consumer electronics, it is very overpriced. You also have to remember that they don't really have to certify it against an accuracy spec like with residential utility power meters, but it is priced as if it is.

None of what you posted seems really that challenging - you need 13.28bits of resolution on an ADC to measure that, coupled with an analog front end to measure 5uV. That seems challenging, until you realize that you have plenty of time to filter - your update rate does not need to be very fast (especially at lower current levels.) (something like a very cheap ADS1115 could do that without any additional amplification) SOC tracking is not that difficult if you are not chasing nW self-consumption numbers like in laptops/cellphones, and also very well documented.

The BMV is one of the most overpriced pieces of Victron equipment. And it is very easily copyable - the hardware is very simple, the communication protocol is open. So should be able to build a copy from Victron's documentation.

https://en.wikipedia.org/wiki/Koeberg_Nuclear_Power_Station#cite_note-wnn-20191018-16

What is the plan? How does the Goodwe interface currently? If you have a protocol and a way to read it, writing an interfacer for emonhub should not take very long.

I see that the Ratel 430p is in stock, I would rather go for that one, if you haven't ordered yet. https://www.communica.co.za/products/ratel-430p

Those 2 together is unlikely to draw more than 10W (as long as you don't have anything power hungry plugged into the USB on the Archer). The Huawei draws quite a lot of current on power-up, that might be a problem, but I don't think it will. At idle these will probably not even be drawing 2W, and I assume they won't be working very hard during loadshedding. Lots of assumptions, yes, but as you say, if they are wrong, it won't be a big issue. The 860p would be a safer bet - with 60W and double the storage, but alas, it is out of stock.

You can get a Ratel 412 from communica for ~R600. It should be able to do everything you want.