Monitoring Gas Bottle Levels with ESPHome, HX711, and Home Assistant

Knowing how much gas is left in a propane or butane bottle is important. It is one of those small things that can make a big difference in everyday life. Whether you’re using gas for grilling, heating, or at a cabin, running out unexpectedly is never convenient. In this guide, we will build a reliable gas bottle monitoring solution. It will be smart using an ESP32, a load cell, and the HX711 amplifier. The solution will be fully integrated with Home Assistant.

This uses the same core principles as water tank monitoring. There are a few important adjustments tailored to gas bottles.

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Why Measure Gas by Weight?

Unlike water tanks with consistent shapes, gas bottles don’t always give accurate readings based on pressure or volume sensors. However, weight is a reliable indicator:

• The empty weight (tare) is fixed
• The gas content has a known maximum (e.g. 11 kg)
• Weight decreases linearly as gas is used

This makes load cells a perfect solution.

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Components Needed

Here’s what you’ll need for this project:

1. ESP32 (M5Stack Atom)

A compact and powerful microcontroller with built-in Wi-Fi. The M5Stack Atom is particularly convenient due to its small size and USB-C power.

2. HX711 Load Cell Amplifier

This module reads very small changes in resistance from the load cell. It converts these changes into digital signals that the ESP32 can process.

3. Load Cell

A strain gauge-based sensor that measures weight. Common types include:

• 5 kg (too small for gas bottles)
• 20 kg (good for small bottles)
• 50 kg (recommended for gas tanks)

Make sure your load cell can handle the total weight of the bottle.

4. Stable Platform

You’ll need a flat and stable surface where the gas bottle can sit on top of the load cell. Mechanical stability is critical for accurate readings.

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Wiring Overview

Typical HX711 to ESP32 connections:

HX711	ESP32
VCC	3.3V
GND	GND
DT	GPIO32
SCK	GPIO26

The load cell connects directly to the HX711 using its four wires.

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ESPHome Configuration

Below is a robust ESPHome configuration with filtering and spike protection. This ensures stable readings even with noise or slight movement.

esphome:
  name: gasstank-vekt
  friendly_name: Gasstank Vekt

esp32:
  board: m5stack-atom
  framework:
    type: arduino

logger:

api:

ota:
  - platform: esphome

wifi:
  ssid: !secret wifi_ssid
  password: !secret wifi_password

bluetooth_proxy:

sensor:
  - platform: hx711
    name: "Gasstank Vekt"
    id: gasstank_sensor
    dout_pin: GPIO32
    clk_pin: GPIO26
    gain: 128
    update_interval: 10s
    unit_of_measurement: "kg"
    accuracy_decimals: 1

    filters:
      - median:
          window_size: 5
          send_every: 1

      - sliding_window_moving_average:
          window_size: 5
          send_every: 1

      - lambda: |-
          if (x < -800000 || x > 100000) {
            return NAN;
          }
          return x;

      - calibrate_linear:
          - -551500 -> 0.0
          - -303029 -> 11.0

      - lambda: |-
          if (x < 0.0) return 0.0;
          if (x > 12.0) return 12.0;
          return x;

  - platform: template
    name: "Gasstank Prosent"
    unit_of_measurement: "%"
    accuracy_decimals: 0
    update_interval: 10s
    lambda: |-
      if (isnan(id(gasstank_sensor).state)) {
        return NAN;
      }

      float percent = (id(gasstank_sensor).state / 11.0) * 100.0;

      if (percent < 0.0) return 0.0;
      if (percent > 100.0) return 100.0;

      return percent;

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Calibration

Calibration is crucial for accuracy.

1. Measure the raw value when the bottle is empty
2. Measure again when full
3. Replace the values in calibrate_linear

Example:

- -551500 -> 0.0
- -303029 -> 11.0

This maps raw sensor values to kilograms.

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Filtering and Stability

Gas bottles don’t change weight rapidly, so we can aggressively filter noise:

• Median filter removes spikes
• Moving average smooths readings
• Lambda filter removes impossible values

This ensures your graphs in Home Assistant look clean and reliable.

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Home Assistant Integration

Once ESPHome is set up, the sensors appear automatically in Home Assistant:

• sensor.gasstank_vekt
• sensor.gasstank_prosent

You can display them in dashboards or use them in automations.

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Useful Automation Example

One of the most practical uses is getting notified before the gas runs out.

YAML Automation

alias: Gas Low Warning
description: Notify when gas bottle is low
trigger:
  - platform: numeric_state
    entity_id: sensor.gasstank_prosent
    below: 20
condition: []
action:
  - service: notify.mobile_app_phone
    data:
      title: "Gas Level Low"
      message: "Gas bottle is below 20%. Time to replace it."
mode: single

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Node-RED Example

If you prefer Node-RED, here’s a simple flow:

1. State node
   • Entity: sensor.gasstank_prosent
2. Switch node
   • Condition: < 20
3. Notification node
   • Send push notification

This gives you a visual and flexible way to manage alerts.

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Advanced Ideas

Once you have this working, you can extend it further:

1. Predict Remaining Time

Track usage over time and estimate how many days are left.

2. Combine with Temperature

Gas usage often correlates with outdoor temperature (in Celsius). You can build smarter predictions.

3. Dashboard Visualization

Use a gauge card in Home Assistant to display percentage clearly.

4. Cabin Monitoring

Perfect for remote cabins where you want to check gas levels before arriving.

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Common Pitfalls

Here are a few things to watch out for:

• Unstable surface → causes fluctuating readings
• Cable noise → keep HX711 wires short
• Poor calibration → leads to wrong percentages
• Temperature drift → minor effect, but can matter outdoors

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Conclusion

You can build a highly reliable gas monitoring system by combining an ESP32, HX711, and a load cell. This system integrates seamlessly with Home Assistant. With proper filtering and calibration, the system becomes stable enough for real-world use and eliminates the guesswork of remaining gas.

This is a simple project with a big quality-of-life improvement—especially for cabins, outdoor kitchens, or anyone relying on gas regularly.