You have many options;
- Iris/ST and some GE wall plugs
- Many Aeon devices like the HEM and a few of their smart switches/dimmers (inwall, micros, and dongles)
- Zooz devices
- GE Zigbee wall switches
- etc, etc, etc.
It all depends on the application. Some appliances may draw too much power, so pay attention to specs for the device and appliance.
If I were you, start with an Aeon HEM just to see what your house is consuming. Then start picking out appliances, and then research in this Community what others may be using for those appliances. The Search feature is your friend! There are many of us with many difference devices. There really isn’t a favorite that I have, and you’ll get varying opinions on what’s good and what works for each individual.
Once you have a plan for your appliances and devices, and you get them working the way you want, start researching what SmartApps are good for you and what your use case is. I personally use Simple Event Logger to dump data to Google Sheets.