Different service call results depending on where the service is called.

[gigatexel]

I'm trying to determine the start of the lowest price interval, based on the epex_spot.get_lowest_price_interval service call.

If I use this service call in the Developers tools:

service: epex_spot.get_lowest_price_interval
data:
  duration:
    hours: 3
  earliest_start: "07:00:00"
  latest_end: "16:00:00"

I get this response:

start: "2024-03-29T12:00:00+01:00"
end: "2024-03-29T15:00:00+01:00"
price_eur_per_mwh: 12.09
price_ct_per_kwh: 1.209
net_price_ct_per_kwh: 1.209

12:00 in localized time is correct!

But when I use the service call like this, in the config-file:

  - trigger:
      - platform: time
        at: 00:00:01
    action:
      - service: epex_spot.get_lowest_price_interval
        data:
          duration:
            hours: 2
          earliest_start: "07:00:00"
          latest_end: "16:00:00"
        response_variable: resp
    sensor:
      - name: start_laagste_prijs
        device_class: timestamp
        state: "{{ resp.start is defined and resp.start }}"

Then the sensor.start_laagste_prijs gets a different value, that is wrong.

[mampfes]

2 observations:

1. You have a duration of 3h in the developer tools and 2h in the config file.
2. 2024-03-29T12:00:00+01:00 represents the same point in time as 2024-03-29T11:00:00+00:00. The first is timestamp includes a timezone offset of 1h which causes the difference.

HA displays timestamps in the entity status view with UTC timestamp (= timezone offset 0). But the timestamp is correct and if you display the sensor value in Lovelace (e.g. an entity card), it will also use your local timezone.

[mampfes]

Any feedback on this?

[gigatexel]

I changed my Apex data generator as follows. This now seems to render the right result:

data_generator: >
      return entity.attributes.data.map((entry, index) => { return [new
      Date(entry.start_time).getTime(), ((0.2040 + entry.price_ct_per_kwh) *
      1.06  ) + (1.582+4.71756+0.20417+5.03288)]; }).slice(new
      Date(hass.states['sensor.start_laagste_prijs'].state).getHours(),new
      Date(hass.states['sensor.start_laagste_prijs'].state).getHours()+3);