I recently encountered an issue with my Home Assistant setup that I thought I’d share with the community in case others are facing similar problems. I created a ‘Delta’ template sensor to measure the temperature difference between a single sensor and a Min/Max Helper, which averages values from nearby rooms. The goal was to ensure our boiler is functioning correctly by monitoring the temperature delta. However, I noticed that the sensor values spiked every time Home Assistant restarted.
Initially, the setup worked smoothly, with the delta value ranging between -1 and +15 degrees. But upon restarts, the Helper or template sensor wasn’t starting in time, causing the calculation to return the full boiler temperature instead of the expected average. This resulted in false spikes on my Lovelace card, which was quite confusing since the heating had been off for hours.
I tried modifying the template sensor to default to 0 if the Helper wasn’t available, but that didn’t resolve the issue. After some research, I discovered that adding a delay to the template sensor initialization helped the Helper start properly before calculations began. Additionally, I implemented a fallback mechanism to handle cases where the Helper was temporarily unavailable.
Here’s the updated template sensor code that worked for me:
yaml
sensor:
- name: boiler_room_temperature_delta
unique_id: ddd99cd0-ddd99cd0-ddd99cd0-ddd99cd0
unit_of_measurement: °C
icon: mdi:thermometer
state: |
{% if is_state(‘sensor.home_temperature’, ‘0’) or is_state(‘sensor.boiler_room_temperature’, ‘0’) %}
0
{% else %}
{{ (((states.sensor.boiler_room_temperature.state | float(0)) - (states.sensor.home_temperature.state | float(0))) | round(1)) }}
{% endif %}
attributes:
delay: 10
fallback: 0
By introducing a small delay and a fallback value, the sensor now initializes correctly after restarts, and the spikes have been eliminated. I hope this solution helps anyone else facing similar issues with template sensors and Helpers in Home Assistant!