question

You can use ESS in the US, it just really depends on the utility most inverters do not have the relevant UL certification.
The GRID code to be selected is "Other" and you can manually fill in the grid parameters but you will need the utility to be okay with this. There are states where this is okay, you just have to check local codes and regulations.

The other option is to use None and have the inverter disconnect from Grid and run in offgrid mode while you have solar/battery. Most people use the GX generator options with wire from GX relay to AUX1 on the inverter for this but NodeRed is a better solution.

I would email salesusacanada@victronenergy.com and ask them to please get the inverters certified, especially the multiplus-II series. If enough people ask I am sure they will do it.

Thanks for the quick reply. Where can I find documentation about the use of the AUX inputs and interfacing them from the GX? The manual shows where they are but I don't see any detail about how to use them.

I know this is an older thread but in the US is there a way to use CTs on the mains to do zero sell back to grid? When grid is down only the critical load panel will be powered.

You do not need it.

Simply setup ACin as GENERATOR and switch the Multiplus to ON.

You do not even need a MultiPlus-II for it.

First of all, if you set it "Generator" then "Feed-In" is automatically disabled, because it is logic, that you can not feed into a Generator.

You can also configure your MultiPlus-II with "ZERO Feed-In".