A few weeks ago I was studying my Ethekwini electricity bill and was wondering how I could use HA as a means of monitoring my geyser usage, so I came up with this idea which seems to work.
I started off by removing the hall sensor IC in a Sonoff DW2 for an interface to HA. A 20A clamp-on...
I tried to run HA from a container under Openmediavault, but there were apparently limitations regarding addons when running from a container, so I went with HAOS directly (on a T520 Thinkpad laptop).