Calculate next night lowest price

[luismsousa]

Hi there,

I'm trying to create an automation to run after the next day rates are published and set a sensor with the lowest night time (00:00-06:00) Agile price so I can schedule devices to charge at that time.

I notice that the next day entity comes in the format of:

  - start: "2024-05-08T02:00:00+00:00"
    end: "2024-05-08T02:30:00+00:00"
    value_inc_vat: 0.15
    is_capped: false

Is there an easy way in HA to iterate over the time map and find the lowest price?

Cheers thanks!

[luismsousa]

So far, I've tried setting a helper template sensor with this template this but with no success:

{% set midnight = (today_at() + timedelta(days=1,)).isoformat() %}
{% set dawn = (today_at() + timedelta(days=1, hours=6)).isoformat() %}
{{ state_attr('event.octopus_energy_electricity_{meter info}_next_day_rates', 'rates') 
| selectattr('start', '>=', midnight) 
| selectattr('start', '<', dawn) 
| map(attribute='value_inc_vat') 
| min }}

this query does return the min value for the whole day:

{{ state_attr('event.octopus_energy_electricity_{meter info}_next_day_rates', 'rates') 
| map(attribute='value_inc_vat') 
| min }}

[BottlecapDave]

Hello. The easiest way would be to use a target rate sensor, with a focus on 0.5 hours and a min-max time set to your desired period. This will turn on/off when the current rate is the cheapest rate. You could then use a template sensor to index into the first item of the target_times attribute. E.g.

{% set rates = state_attr('binary_sensor.octopus_energy_target_{{TARGET_RATE_NAME}}', 'target_times') %}
{% if rates is not none and rates | length > 0 %}
{{ rates[0]["value_inc_vat"] }}
{% endif %}

[luismsousa]

many thanks @BottlecapDave I was definitely trying to reinvent the wheel.
That works like a charm ⭐

[luismsousa]

If anyone in the future comes looking for a way to set your house battery to charge at night for 3 periods of 30 mins, here's what I did.

• Used the above target sensor with a focus of 2 (4 blocks of time, of which I'll choose the lowest 3 to charge).
• Set a helper template sensor called lowest_night_rate_next_day to fetch the 4th value in the array:

{% set rates = state_attr('binary_sensor.octopus_energy_target_nighttime_rate', 'target_times') %}
{% if rates is not none and rates | length > 0 %}
{{ rates[3]["value_inc_vat"] }}
{% endif %}

• Set an automation that runs at 5pm and checks if the sensor value is below my export rate (in my case 15 pence) and sets a helper value that my inverter automation then polls to trigger the charge/discharge logic.

alias: Set night time charging price threshold
description: >-
  Check the next_day import rates and select the lowest price between 00:00 and
  06:00
trigger:
  - platform: time_pattern
    hours: "17"
    minutes: "00"
    seconds: "00"
condition: []
action:
  - choose:
      - conditions:
          - condition: numeric_state
            entity_id: sensor.lowest_night_rate_next_day
            below: 0.15
        sequence:
          - service: input_number.set_value
            metadata: {}
            data_template:
              entity_id: input_number.target_energy_price
              value: "{{ states('sensor.lowest_night_rate_next_day') }}"
    default:
      - service: input_number.set_value
        metadata: {}
        data:
          value: 0.15
        target:
          entity_id: input_number.target_energy_price
mode: single

[luismsousa]

@BottlecapDave , I'm happy to write a small blurb to add to https://github.com/BottlecapDave/HomeAssistant-OctopusEnergy/blob/develop/_docs/community.md and raise a PR if you feel it would useful for other users.

[BottlecapDave]

I'm glad you managed to solve your problem. I think this discussion is enough for anyone that might need this sort of issue. The community page is meant for highlighting other integrations that use this integration and generic config where I got quite a few requests (existed before discussions were enabled).