Probably the best most cost-effective home energy monitoring (sorry its wifi and not Z-Wave or Zigbee) out there today is Emporia Energy.
I just installed the Model 3 with 3 phase support and 16 channels.
Any chance for Cloud API integration with Emporia Energy?
Here is the catch, they have an API available but you have to have a partner account (I have access to one and why I know they have an API). That said EZLO could become a partner, resell the Emporia Energy devices and then be able to offer users integration.
Reportedly there are some open source projects, but I haven’t taken the time to look at them.