EPEX SPOT

An Spot Tariff component provides day-ahead electricity prices for bidding zones. It can be used in both Edge and Backend versions of OpenEMS.

Time-Of-Use price components depending on spot prices

  • Tariff.BySpotTariff.GridBuy: Provides an grid buy price based on spot price, ancillary costs and a calculation formula

  • Tariff.BySpotTariff.GridSell: Provides an grid sell price based on spot price and a calculation formula

  • Tariff.Manual.EEG2025.GridSell: Provides a static sell price, but returns zero if the spot price is negative

Components that provide the day-ahead epex spot prices

  • Tariff.SpotTariff.ENTSOE: Retrieves prices from the ENTSO-E Transparency Platform, available in edge & backend

  • Tariff.SpotTariff.SMARD: Retrieves prices from the SMARD platform, available in edge & backend

  • Tariff.SpotTariff.FromBackend: Retrieves prices from backend provider, available in edge only

Spot price aggregation

When multiple components are configured, the system will summarize the prices in the following matter: 1. Always fetch all prices from all configured components. 2. Identify the period for which we have prices. 3. Iterate through all spot tariff components (sorted by service_ranking - highest first) and use the first available price for each 15min time slot. 4. The price is always converted to the same currency. In Edge systems, that’s the configured currency in the Core.Meta component. In Backend systems, that’s the default currency of the Bidding Zone.

If no currency exchange rate is available, the price is ignored.

In Edge, the PriceManagerImpl class is responsible for aggregating the prices. You can get the spot prices by injecting the PriceManager service. In Backend, the BackendTariffManagerImpl class is responsible for aggregating the prices. You can get the spot prices by injecting the TariffManager service. The SpotTariffSyncManager service is responsible to synchronize the backend prices to all edge systems.

Currency Conversion

Currency conversion is done using the CurrencyExchange service. The exchange rates from ECB Exchange Rates API are used. Edge tries to fetch the exchange rates from Backend. If no backend is available, the exchange rates are directly fetched.

Tariff.BySpotTariff.GridBuy component

This component provides an grid buy price based on spot price, ancillary costs and a calculation formula. If a specific time slot does not have a spot price, the system will use the last known price for the previous time slot.

Ancillary costs

Ancillary costs can be provided in the Tariff.BySpotTariff.GridBuy component configuration. It’s a JSON string defining additional costs on top of the day-ahead price.

You can configure ancillary costs in two ways: by using a predefined German Distribution System Operator (DSO) or by providing a custom schedule.

Using a Predefined DSO

For convenience, several German DSOs are already predefined in the implementation. For example:

{
  "dso": "BAYERNWERK"
}

Configuration example:

  • biddingZone: GERMANY

  • ancillaryCosts: {"dso":"BAYERNWERK"}

For a list of predefined DSOs see GermanDSO.java.

Using Custom Ancillary Costs (DSO = "OTHER")

If your DSO is not on the predefined list, or if you need to define a custom time-of-use tariff structure, you can provide your own schedule.

In this case, set "dso": "OTHER" and provide a schedule array with quarterly definitions.

Each entry in the schedule contains:

  • year: calendar year (e.g., 2025)

  • tariffs: fixed additional costs (per kWh) for each tariff level (low, standard, high)

  • quarters: quarterly schedules (Q1–Q4) with dailySchedule definitions

Example configuration:

{
  "dso": "OTHER",
  "schedule": [
    {
      "year": 2025,
      "tariffs": {
        "low": 0.10,
        "standard": 0.20,
        "high": 0.30
      },
      "quarters": [
        {
          "quarter": 1,
          "dailySchedule": [
            { "tariff": "low", "from": "00:00", "to": "06:00" },
            { "tariff": "standard", "from": "06:00", "to": "18:00" },
            { "tariff": "high", "from": "18:00", "to": "23:59" }
          ]
        },
        {
          "quarter": 2,
          "dailySchedule": []
        },
        {
          "quarter": 3,
          "dailySchedule": []
        },
        {
          "quarter": 4,
          "dailySchedule": [
            { "tariff": "low", "from": "00:00", "to": "06:00" },
            { "tariff": "standard", "from": "06:00", "to": "18:00" },
            { "tariff": "high", "from": "18:00", "to": "23:59" }
          ]
        }
      ]
    }
  ]
}

Custom Schedule JSON Structure Explained

The schedule is a JSON array where each object defines the tariffs for a specific year.

  • year:: The year for which this schedule is valid (e.g., 2025).

  • tariffs:: An object defining the named price levels. You can define your own names (e.g., low, standard, high) and assign a cost to each. The name standard is special and is used as a fallback if no time slot applies.

  • quarters:: An array defining the schedule for each quarter of the year.

    • quarter:: The quarter number (1 to 4).

    • dailySchedule:: An array specifying the time slots and their corresponding tariffs for each day in that quarter.

      • tariff:: The tariff name, which must match one of the keys defined in the tariffs object.

      • from:: The start time of the slot in HH:mm format.

      • to:: The end time of the slot in HH:mm format.

Notes

  • If the dailySchedule for a quarter is empty ([]), the system will default to using the price defined for the standard tariff for that entire quarter. This is useful for seasons with flat ancillary costs.

  • Tariff boundaries (from/to) must not overlap and must follow chronological order.

  • Multiple years can be defined by adding more entries to the schedule array.

Source Code