I use the Sonoff Pow2 running Tasmota which outputs using MQTT. I then use NodeRED to send to emoncms. I have one on a dehumidifier. I have a NodeMCU with an SHT21 and BMP280 measuring temp and humidity (in and out). These go to OpenHAB via MQTT. I have a control in OpenHAB which looks at the average humidity over the last hour and when that gets too high it turns on the dehumidifier and when the average drops it turns off the dehumidifier off. This works great and keeps the efficiency up. I have a tipping bucket rain gauge connected to the NodeMCU which keeps track of the water coming out. I have a block in NodeRED that measures the efficiency (buckets/KWh) and sends that to emoncms. Even with all of this the actual efficiency is way less than specified. But, that is expected as they are specified at the point where they are really efficient, hot and really, really, really humid. Mine is in a cool area that is relatively dry. There is a seasonal difference, as outside temperature/humidity really impacts what is going on inside.
In the US the Sonoff S31 is my new favorite, as it is much smaller. Tasmota is a really great open source program on GitHub.