T-Forecast

A T-forecast stands for transport forecast. In practice, we often call this a day-ahead forecast. It is a detailed overview of your expected electricity consumption or generation for the following day.

Do you have a large-scale business connection greater than 1 megawatt (MW)? Then you are legally required to provide this estimate under the Electricity System Code. You must submit this day-ahead forecast daily by 14:30 at the latest. This ensures that grid operators know exactly what load to expect on the electricity grid. It helps to utilize the grid optimally and prevents outages.

“T-forecasts are required for all aspects of the electricity market and must also be submitted for non-dispatchable assets. Therefore, they can not be submitted to GOPACS.”

How does the submission work?

The submission is done per connection (EAN code) and must always be processed via a party registered and qualified with TenneT: the so-called Forecast Provider. You can arrange this in one of three ways:

1. Your Balance Responsible Party (BRP) prepares the forecast and sends it to the grid operator.
2. You choose an external Forecast Provider from TenneT’s official list and ask them to prepare and submit the forecast.
3. You qualify your own company as a Forecast Provider with TenneT and manage the submission entirely yourself.

Although the initial submission must take place strictly before 14:30, the series can be updated continuously (intraday) afterwards. This allows you to adjust the forecast even more accurately on the day itself, for example in case of changing weather conditions for solar parks.

Technical structure and data

The T-forecast is strictly structured according to national market standards:

• Protocol & Message: The data is structured according to the national GLDPM protocol and is sent in a digital XML file, the so-called GLMD message.
• Time blocks (PTUs): The forecast is divided per Program Time Unit (PTU), which equates to 96 fifteen-minute intervals per day (showing the expected power in MW for every quarter of an hour between 00:00 and 23:59).
• Four time series: For each quarter of an hour, the message contains four specific time series:
  1. The estimated consumption
  2. The estimated production (generation)
  3. The reactive power
  4. The consumption by production units (own consumption of a power plant or installation, for example)

Quality monitoring by grid operators

The electricity grid must remain reliable and affordable. That is why the joint grid operators (such as Stedin, Liander, and Enexis) structurally monitor the submitted day-ahead forecasts. They check the accuracy, timeliness, and completeness of the data.

The grid operator examines to what extent your forecast matches the actual measured values. This helps to signal deviations at an early stage. It also gives grid operators better insight into the actual use of the power grid. As a result, we can, for example, help companies on the transport capacity waiting list more quickly.

More information

Do you have questions about submitting T-forecasts to a specific grid operator? Please check one of the pages below:
Enexis > Dagprognoses
Liander > Dagprognoses
Stedin > Dagprognoses
TenneT > Prognoses

Back to Glossary