I'm a zigbee fan, mostly because there's such a wide variety of devices.
I almost exlusively use zigbee2mqtt [0] reference to find devices that suit me. Searching for `meter` gives a lot of options, you'd have to do more investigation to find something that supported 40A, but my guess would be that a clamp meter is likely your best option.
It's also possible that you could use one of the DIN rail options in your fusebox, but I haven't looked at the current ratings.
I almost exlusively use zigbee2mqtt [0] reference to find devices that suit me. Searching for `meter` gives a lot of options, you'd have to do more investigation to find something that supported 40A, but my guess would be that a clamp meter is likely your best option.
It's also possible that you could use one of the DIN rail options in your fusebox, but I haven't looked at the current ratings.
[0] https://www.zigbee2mqtt.io/supported-devices/#s=meter