template:
  - trigger:
      - trigger: time
        at: "01:05:00"
        variables:
          price: "{{ states('sensor.nord_pool_se4_daily_average') | float(0) }}"
          first: |
            {% set d = state_attr('sensor.dynamic_electricity_price', 'date') %}
            {{ d is none or as_datetime(d).strftime('%Y-%m') != now().strftime('%Y-%m') }}        
    condition: "{{ price > 0 }}"
    sensor:
      - name: "dynamic electricity price"
        unique_id: dynamic_electricity_price
        state: | 
          {% set sum = 0 if first else this.attributes.sum %}
          {% set count = 1 if first else 1 + this.attributes.count %}
          {{ ((sum + price) / count) | round(4) }}
        attributes:
          date: "{{ now() }}"
          sum: "{{ price if first else price + this.attributes.sum }}"
          count: "{{ 1 if first else 1 + this.attributes.count }}"