Zone Definition¶

Wattnet defines zones as distinct geographical areas for which energy generation and exchange data is collected and environmental impact metrics are then calculated.

Spatial Granularity of Zones in Wattnet¶

To define the spatial granularity of zones, Wattnet primarily relies on existing administrative boundaries and energy market regions, as these are the standard reference points for energy data reporting. Since Wattnet's main data source is ENTSO-E, the following zone definitions are used, reflecting common practice in the European energy market:

Zone Definitions¶

• Country: A country is a recognized territorial and political entity. Countries are often used as reporting zones due to the availability of national-level statistics and established regulatory frameworks.
• Bidding Zone (BZN): A bidding zone is the largest area within which market participants (producers and consumers) submit their offers and bids without being affected by internal grid constraints. It reflects the economic segmentation of the electricity market.
• Control Area (CTA): A control area is a defined part of the transmission grid for which a specific transmission system operator (TSO) is responsible. The TSO ensures real-time balance between electricity generation and consumption, and maintains grid stability.

Granularity Strategy¶

Wattnet always aims to use the most spatially granular data available. Therefore, when multiple zone definitions exist for the same geographical area, the smallest available zone is prioritized. For example, if both bidding zone and country-level data are available for a region, bidding zone data will be used.

Each geographical area has an associated EIC code (Energy Identification Code), which uniquely identifies the zone in energy market data. See the EIC code list for reference.

However, data availability and granularity vary across regions, and practical implementation must adapt accordingly. The following examples illustrate these differences.

Regional Examples¶

Standard cases¶

• The majority of European countries (e.g., France, Spain, Poland) are defined as one country, one bidding zone, and one control area. In these cases, all three definitions align perfectly.

Exceptions¶

Some regions differ due to unique market structures or geopolitical factors:

• Italy: One country. Multiple bidding zones (North, Central North, Central South, South, Sicily, Sardinia, Calabria). One control area.
  • Bidding zones are used.
• Sweden: One country. Four bidding zones (North, Central North, Central South, South). One control area.
  • Bidding zones are used.
• Norway: One country. Five bidding zones (Southeast, Southwest, Central, North, West). One control area.
  • Bidding zones are used.
• Denmark: One country. Two bidding zones (East and West). One control area.
  • Bidding zones are used.
• Germany: One country. Bidding zone includes Germany + Luxembourg, 4 control areas (50Hertz, Amprion, TenneT, TransnetBW).
  • No cross-border physical flows data between control areas, so country-level data is used.
  • No data at "country-to-bidding-zone" level between Germany and Denmark (which has two bidding zones). This is taken into account when calculating exchanges.
• United Kingdom of Great Britain and Northern Ireland & Ireland: Two countries. Two bidding zones. Three control areas.
  • Northern Ireland belongs to the UK politically, but to the Ireland bidding zone.
  • Three control areas: Great Britain, Northern Ireland, and Ireland.
  • Control area data is used. Data exists at "control-area-to-control-area" level.
• Ukraine: One country. One bidding zone. Two control areas.
  • No control area data available, so country-level data/bidding zone data is used.
• Russian Federation: One country and one control area. Each has multiple bidding zones (Russia, Kaliningrad).
  • Bidding zones are used.

Conclusion¶

These examples show how zone definitions often overlap, but are not always perfectly aligned. Wattnet uses the most granular data available, while adapting to the specific market structures and data availability of each region.

Current Zone List¶

The following table lists the zones currently defined in Wattnet, along with their attributes:

Temporal Granularity¶

The temporal granularity in Wattnet refers to the time intervals at which energy generation and exchange data are collected and reported for each defined zone. The same temporal resolution is used to compute environmental impact metrics.

The ENTSO-E Transparency Platform provides data at different temporal resolutions depending on the data type and the specific zone(s) involved. The most common temporal granularities are hourly, 30-minute, and 15-minute intervals. There is no direct mapping between zone definitions and temporal granularities, as these may vary over time.

Wattnet Temporal Granularity Strategy¶

Wattnet aims to use the most granular useful data available for each zone while ensuring consistency and comparability across all zones. A minimum temporal granularity of 15 minutes is defined for all zones, so all data is processed and reported at this interval.

This approach is possible because ENTSO-E reports average power (in Watts) for each time interval, not total energy (in Watt-hours). Power (W) is an instantaneous or average rate of energy generation or consumption, meaning it is independent of the interval length. Therefore, a value reported as the average power over 1 hour can be applied to shorter intervals (e.g., four 15-minute segments) without inconsistency. In such cases, the same value is repeated across all 15-minute intervals within the hour.

For zones that report data natively at 15-minute intervals, the power values naturally vary every 15 minutes. But for zones with coarser resolutions (like hourly), replicating the reported average power across finer intervals maintains internal consistency and enables uniform 15-minute granularity across the system.

This strategy enables Wattnet to compute standardized and comparable environmental impact metrics at a high temporal resolution (15-minute intervals) for all zones, while preserving data integrity and remaining faithful to the nature of the original data.

Data Files¶

The zone definition data files used by Wattnet are published at github.com/wattnet/wattnet-data/tree/main/zones.