Monitor and control Remeha hybrid heat pump system

My house is equipped with the following Remeha system

  • Elga Ace 4kw heat pump
  • Tzerra Ace-Matic gas heater
  • eTwist thermostat

Searching around the forum I have found some information, but there are still gaps in my understanding.

If you just want to control your eTwist with HA, there is an extension for that which uses the Remeha cloud API: GitHub - msvisser/remeha_home: Remeha Home integration for Home Assistant

The local situation is a bit complicated it seems. As far as I understand the gas heater and heat pump both automatically switch between R-bus, OpenTherm, and on/off thermostats. OpenTherm gateways are available from Nodo-shop and DIYLESS. However, the eTwist uses R-bus, which is a proprietary Remeha protocol. To connect it as an OpenTherm device, a Remeha GTW16 gateway is needed. So AIUI the connection is:

gas heater ↔ heat pump ↔ OTGW ↔ GTW16 ↔ eTwist

Or if you’re feeling courageous, replace the entire thermostat with an OpenTherm one. DIYLESS also seems to sell complete thermostats so you wouldn’t even need a gateway.

But honestly the most interesting thing to me is to monitor the energy usage of my heat pump. It does not appear that there is an OpenTherm message ID corresponding to energy use. Am I missing something?

I’m thinking maybe I should just add a Zigbee energy meter? Challenge is that typical devices only go up to 16A or 3kw, so a more heavy duty device is required to measure the 4kw heat pump. Any ideas?