Hi!

I considering monitoring and controlling a water heater. The water heater is a smart one that will use the current hourly electricity rate to turn on and off. However, in Norway, we also have an extra charge if we use a high electricity load for an hour. I would like to turn off the heater if the total load is above 10kW in the house. The idea is that if the total load meets the threshold I would use the available open API to turn off the water heater. If the load is lower it should turn it on again. 

I'm not sure if I can call API from Iammeter or if I can use something else, such as Home Assistant or MQTT

https://api.osoenergy.no/water-heater-api-swagger/index.html 

Thanks that should work! Now I need to buy and get the water heater installed!

I use home assistant that controls a non modified Sonoff switch

Installed the docker container, and set it up.

Note using three phase meter to control this

Two automations one to turn on hotwater when the switch state is off and the generation total would be higher than the total consumption if the hotwater was turned on

Second automation to turn off the hotwater if the switch state is on and the consumption is greater than the generation output

Doing it this way you have a 1 minute max lag either way, but for me that was much better than paying for the power on cloudy rainy days and not have to think about it. I am not so sure why there is a need for this lag to homeassistant since the docker container app is capturing this data every second.

There is an article that goes through all of this setup as well, I went down this path because I wanted this information in homeassistant as well, and pvoutput https://pvoutput.org/list.jsp?userid=32148. If you want to have a look at this in action here is my pvoutput page, note any spikes over are consumption shown are likely to be induction cooktop, kettle or oven.