This blueprints uses the nordpool integration and lets you choose howe many hours you will define as expesive, and make a sensor block temperature based on that information.

block_heat.yaml

blueprint:
  name: Block heat (15-min safe)
  description: >
    Blockerar värme (sätter virtuell temperatur) under de dyraste timmarna baserat
    på Nordpool-priser. Under billiga perioder speglar den utetemperaturen med
    ett valt uppdateringsintervall. Fungerar med 60- och 15-minuterspriser samt DST.
  domain: automation
  input:
    grid_area:
      name: Grid Area Sensor
      description: Din Nordpool-prissensor
      selector:
        entity:
          domain: [sensor]
          integration: nordpool
          multiple: false
    expensive_hours:
      name: Expensive Hours
      description: Antal timmar att blockera (omvandlas till slots automatiskt)
      default: 4
      selector:
        number:
          min: 0.0
          max: 24.0
          mode: slider
          step: 1.0   # sätt 0.25 om du vill ha kvartsteg
    temperature_sensor:
      name: Temperature Sensor
      description: Din riktiga utetemperatursensor
      selector:
        entity:
          domain: [sensor]
          device_class: [temperature]
          multiple: false
    refresh_temperature_delay:
      name: Cheap Hours - Refresh Controllable Temperature Delay Time
      description: Hur ofta den kontrollerbara temperaturen ska spegla ute-tempen under billiga perioder.
      default: 5
      selector:
        number:
          min: 0.0
          max: 10.0
          step: 0.25
          unit_of_measurement: Minutes
          mode: slider
    controll_sensor:
      name: Controllable Sensor
      description: Din kontrollerbara sensor (t.ex. MQTT number)
      selector:
        entity:
          domain: [number]
          integration: mqtt
          multiple: false
    virtual_temperature:
      name: Virtual Block Temp
      description: Virtuell temperatur under dyra perioder (för att blockera värmen)
      default: 20
      selector:
        number:
          min: 0.0
          max: 30.0
          mode: slider
          step: 1.0
          unit_of_measurement: "°C"
  source_url: https://gist.github.com/JohanAlvedal/66b21a648a1a4ca261f6f3476b3f82e3

variables:
  grid_area: !input grid_area
  expensive_hours: !input expensive_hours
  temperature_sensor: !input temperature_sensor
  refresh_temperature_delay: !input refresh_temperature_delay
  controll_sensor: !input controll_sensor
  virtual_temperature: !input virtual_temperature

trigger:
  - platform: state
    entity_id: !input grid_area
  - platform: homeassistant
    event: start
  - platform: time_pattern
    seconds: 30

mode: restart

action:
  - choose:
      - conditions:
          - condition: template
            # DYRT nu? -> blockera (sätt virtuell temperatur)
            value_template: >
              {% set cur = states(grid_area) | float(default=none) %}
              {% set raw = state_attr(grid_area, 'raw_today') or [] %}
              {% if cur is none or raw | length == 0 %}
                false
              {% else %}
                {% set prices = raw | map(attribute='value') | map('float') | list %}
                {% set L = prices | length %}
                {% set slots = (expensive_hours * L / 24) | int %}
                {% set slots = 1 if slots < 1 else (L if slots > L else slots) %}
                {% set threshold = (prices | sort)[L - slots] %}
                {{ cur >= threshold }}
              {% endif %}
        sequence:
          - service: number.set_value
            target:
              entity_id: !input controll_sensor
            data:
              value: !input virtual_temperature

      - conditions:
          - condition: template
            # BILLIGT nu? -> spegla ute-temp, repetera tills det blir dyrt
            value_template: >
              {% set cur = states(grid_area) | float(default=none) %}
              {% set raw = state_attr(grid_area, 'raw_today') or [] %}
              {% if cur is none or raw | length == 0 %}
                false
              {% else %}
                {% set prices = raw | map(attribute='value') | map('float') | list %}
                {% set L = prices | length %}
                {% set slots = (expensive_hours * L / 24) | int %}
                {% set slots = 1 if slots < 1 else (L if slots > L else slots) %}
                {% set threshold = (prices | sort)[L - slots] %}
                {{ cur < threshold }}
              {% endif %}
        sequence:
          - alias: Refresh controllable temperature during cheap period
            repeat:
              until: >
                {% set cur = states(grid_area) | float(default=none) %}
                {% set raw = state_attr(grid_area, 'raw_today') or [] %}
                {% if cur is none or raw | length == 0 %}
                  true
                {% else %}
                  {% set prices = raw | map(attribute='value') | map('float') | list %}
                  {% set L = prices | length %}
                  {% set slots = (expensive_hours * L / 24) | int %}
                  {% set slots = 1 if slots < 1 else (L if slots > L else slots) %}
                  {% set threshold = (prices | sort)[L - slots] %}
                  {{ cur >= threshold }}
                {% endif %}
              sequence:
                - service: number.set_value
                  target:
                    entity_id: !input controll_sensor
                  data:
                    value: "{{ states(temperature_sensor) | float(0) }}"
                - delay:
                    minutes: !input refresh_temperature_delay
    default: []