This is what I use on the house now :
On the power usage test I did I used this :
(Well, its not EXACTLY this, but uses the same chipset)
Now the HA system I use :
Any two of the devices come up less then that device and you’d get a heap of functionality.
Another other way would be a RPi with a Z Wave ‘HAT’ then poll them that way.
An example use case is me and the wife went on vacation to CA last year. The mother in law stayed home. Both me and her got a push notification @ 3AM EST that the power usage jump up to 4700W and it was a abnormal behavior (as it looks at trends). My wife opened up the app, went to the section that had the kitchen- fired up the security camera app and saw that the oven was on with a pot on it. Then she was able to kill the power (220V) to the oven remotely. That- was worth the price of admission. As that could have gone sideways pretty quickly.