Below Average.yaml

template:
  - sensor:
      - name: Under gennemsnit
        state: >
          {% set start_time = now().hour %}
          {% set prices = (state_attr("sensor.elpris", "today") + state_attr("sensor.elpris", "tomorrow"))[start_time:] %}
          {% set index = prices.index(prices | select('lt', prices | average) | first) %}
          {{today_at("00:00") + timedelta(hours = index + start_time)}}

card.yaml

type: custom:html-template-card
ignore_line_breaks: true
content: >
  {% set value = states("sensor.billigste_time") | as_datetime %} <div
  style="display:flex;
  flex-direction:column;align-items:center;padding:20px;text-align:center">
    Start strømslugere{{" om" if value > now() }}:
    {% if value > now() -%}
    <h1>{{'%02d' % ((value - now()).total_seconds() / 60 / 60) | round(0, 'floor')}}:{{'%02d' % ((value - now()).total_seconds() / 60 % 60) | round(0, 'floor')}}</h1>
    {%- else -%}
    <h1>NU</h1>
    {%- endif %}
  </div>

Cheapest Hour.yaml

template:
  - sensor:
      - name: Billigste time
        state: >
          {% set start_time = now().hour %}
          {% set prices = (state_attr("sensor.elpris", "today") + state_attr("sensor.elpris", "tomorrow"))[start_time:] %}
          {% set index = prices.index(prices | min) %}
          {{today_at("00:00") + timedelta(hours = index + start_time)}}

Sensor-Formatted.yaml

template:
  - sensor:
      - name: Billigste time
        state: >
          {% set start_time = now().hour %}
          {% set prices = (state_attr("sensor.elpris", "today") + state_attr("sensor.elpris", "tomorrow"))[start_time:] %}
          {% set index = prices.index(prices | min) %}
          {{"I morgen " if index + start_time >= 24}}kl {{((today_at("00:00") + timedelta(hours = index + start_time))).strftime('%H:%M') }}