Sensor that shows change in temperature

Configuration
1

Is it possible make a sensor that takes the current value of another sensor and compares it with the state of the same sensor an hour back in time?

I want to see if the temp in my house has gotten colder or hotter compared to an hour ago and also for the sensor to show the difference in +C och -C. Even better would be in green color or blue color depending on positive or negative.

I have tried using the binary_sensor but I’m not getting any good results and I dont even know if it would do the job as I want it to show in the end.

binary_sensor:

  • platform: trend
2

If you just want to visualize it, take a look at the new sensor card or if you are on the old UI the history graph component works.

https://www.home-assistant.io/components/history_graph/

I do this exact thing in my configuration.

3

Are you using influxdb? If so, you can use the influxdb sensor to fetch historic values and perform mathematical functions for you.

4

Since I’m using a pretty small tablet to view everything in the house I’m just interested in a small single value sensor that doesnt take much space. I’m using influx/grafana and have a couple of graphs through a panel_iframe there but in this particular case I just want a number that fits my already overwhelmed dashboard :slight_smile:

since we already can subtract a sensor value from another sensor, all we need in this case is to fetch or store a value every hour to be used for subtraction. I guess this can be done with an automation of some sort. I just wondered if there was some kind of complete solution or component that I have missed. It would be a very nice feature to have in a monitoring system, seems pretty standard to me also :slight_smile:

5

What if I make an input_number sensor, how can I then use it in an automation to store a value from an existing sensor in it?

If I can achieve this then I think the case is solved with a template sensor:
“current-sensor” minus “input_number sensor” that gets its value stored with the automation every hour.

6

Does this help? https://www.home-assistant.io/components/binary_sensor.trend/

There are a number of utility sensors you might like to look through.

7

Why not simply use the statistics sensor? https://www.home-assistant.io/components/sensor.statistics/

This would give you the change over the defined period (and some other statistics) as attribute which you can then use to create a template sensor. Something like this:

sensor:
  - platform: statistics
    name: temp_stats_1h
    entity_id: sensor.your_temperature_sensor
    max_age:
      minutes: 60

  - platform: template
    sensors:
      temp_change_1h:
        value_template: "{{ state_attr('sensor.temp_stats_1h_mean','change') }}"
        unit_of_measurement: '°C'
2 Likes
8

wow, this seems to be exactly what I’m looking for. I’ll give it a go tonight!

Nickrout: I’ve tried that one, firstly I’m doing something wrong and cant get it working correctly… but secondly I dont think it returns a calculated value back like I want. It only gives a trend “up” och “down” value I think?

9

I would use influxdb sensor to retrieve the value from 1 hour ago and then a template sensor to find the difference between current value and old value.

10

Why influxdb? There is a component to access the home assistant database.

Anyway looks like @Mattie has it sorted :slight_smile: I find all those utility sensors quite confusing and generally have to experiment to get them right.

11

So easy when you know what to do, this worked like a charm! Thank you very much sir! :slight_smile:

12

Hey Mattie,

I stumbled over this post and I’d be really curious what that code looked like on your end.
I got a similar idea, but not with temperatures.
I’d like to record the daily change of the corona virus infections compared to the day before.
My code currently looks like this:

- platform: statistics
  name: current_stats_1h
  entity_id: sensor.worldwide_coronavirus_confirmed
  max_age:
     minutes: 10

- platform: template
  sensors:
    sensornametest:
      value_template: "{{ state_attr('sensor.current_stats_1h_mean','change') | int}}"
      unit_of_measurement: "people"

But somehow it doesn’t give me anything. :frowning:

13

Hey MrBenedict,

my code looks like below, hope it helps :slight_smile:

  - platform: statistics
    name: utomhus_stats
    entity_id: sensor.utomhus_temperature
    max_age:
      minutes: 60

  - platform: template
    sensors:
      utomhus_trend:
        friendly_name: Utomhus
        value_template: "{{ state_attr('sensor.utomhus_stats','change') }}"
        unit_of_measurement: '°C'
        icon_template: >-
          {%- if state_attr('sensor.utomhus_stats','change') | float < 0.01 %}
            mdi:arrow-down-bold
          {% else %}
            mdi:arrow-up-bold
          {% endif %}
1 Like
14

I’m trying to set this up at my end, but I’m having some issues:

My code looks like this:

    name: livingroom temperature stats
    entity_id: sensor.atc_livingroom_temperature
    max_age:
      minutes: 60

  - platform: template
    sensors:
      outdoor_temp_trend:
        friendly_name: Livingroom temperature trend
        value_template: "{{ state_attr('livingroom_temperature_stats','change') }}"
        unit_of_measurement: '°C'
        icon_template: >-
          {%- if state_attr('livingroom_temperature_stats','change') | float < 0.01 %}
            mdi:arrow-down-bold
          {% else %}
            mdi:arrow-up-bold
          {% endif %}

Trend returns unknown

If I try to check the template {{ state_attr('livingroom_temperature_stats','change') }} in developer tools, it returns null.

Any idea why is this happening?

15

Actually my two sensors also happen to return unknown since a few weeks ago, I havent had the time to investigate it but now I’m almost wondering if it has something to do with the later versions…? I’ll write here if I find the time to check

1 Like
16

Fixed it.
There is a breaking change in 2021.12.

New code looks like this:

  - platform: statistics
    name: livingroom temperature stats
    entity_id: sensor.atc_livingroom_temperature
    state_characteristic: change
    max_age:
      minutes: 60

  - platform: template
    sensors:
      indoor_temp_trend:
        friendly_name: Livingroom temperature trend
        value_template: "{{ states('sensor.livingroom_temperature_stats') }}"
        unit_of_measurement: '°C'
        icon_template: >-
          {%- if states('sensor.livingroom_temperature_stats') | float < 0.01 %}
            mdi:arrow-down-bold
          {% else %}
            mdi:arrow-up-bold
          {% endif %}
2 Likes
17

Nice, I guess I’m the one who will be thanking you :slight_smile:

1 Like
18

state_characteristic: change

wast this the only difference? I’m still not getting mine to work

19

nevermind, missed the attribute change