Homeassistant Gazpar Zigbee

How to get (almost) real time gas usage metric from a Gazpar meter using a zigbee button and Home Assistant

Based on ¹.

Disclaimer

As with any DIY project there is a chance of damage or injury and we are dealing with gas. Follow this guide at your own risk.

What you need

• Home assistant
• A Gazpar meter or compatible
• a Zigbee button, I recommend an Ikea one because they have a magnet on the back and the meter has a steel casing
• a JAE connector. Either buy one or print one, instruction below

How it works

The Gazpar has a dry contact that closes for 300ms every 10L of gaz.

We can use this dry contact to close a zigbee switch that triggers a Home Assistant automations which in turn increment a counter.

Hardware

If you do not have a pre-made cable, you can use the Gazpar-MX44-Connector.3mf file for prusaslicer with pre-configured supports, originally from². Just add Dupont female connectors and some hot glue to secure them.

Just solder the cable across a switch of your Zibgee button. Plug the connector into the side of your meter.

Software

I'm using Zigbee2Mqtt but you can use other systems, you'll need to adapt the trigger.

Input counter

This is the variable that stores the amount of Liters that have been used.

input_number:
  gas_counter:
    min: 0
    max: 100000000000
    name: gas_counter
    icon: "mdi:gas-station"
    mode: box

Automation

This increment the counter above by 10 every time the zigbee button is "pressed" (read: the dry contact is closed).

automation:
  - alias: ⛽️ Increment gas counter
    trigger:
      - platform: mqtt
        topic: zigbee2mqtt/<name of the button>/action
        payload: '<state when it's pressed>'
    action:
      - service: input_number.set_value
        data:
          value: "{{ states('input_number.gas_counter') | int + 10 | int }}"
        entity_id: input_number.gas_counter
    mode: single

Volume sensor

This will create a sensor in cubic meters as Home assistant will require it for the gas utility meter and the dashboard.

template:
  - sensor:
    - name: "Gas Volume"
      unit_of_measurement: 'm³'
      state: "{{ states('input_number.gas_counter') | int / 1000 | round(3) }}"
      device_class: gas
      state_class: total

You can now add it to your energy dashboard!

Utility meter

Used for stats:

utility_meter:
  gas_total_usage_daily:
    source: sensor.gas_volume
    cycle: daily
  gas_total_usage_weekly:
    source: sensor.gas_volume
    cycle: weekly
  gas_total_usage_monthly:
    source: sensor.gas_volume
    cycle: monthly
  gas_total_usage_quarterly:
    source: sensor.gas_volume
    cycle: quarterly
  gas_total_usage_yearly:
    source: sensor.gas_volume
    cycle: yearly

Sources

Footnotes

1. Home Assistant: récupération Gazpar ↩

2. Gazpar connector ↩