Evolution of Belgian Tertiary Reserve Market


As opposed to Primary Reserve (R1) and Secondary Reserve (R2) that imply to deliver electricity in seconds by following automatic signals; Tertiary Reserve (R3) grants a 15 minutes reaction time that makes it more easily suitable for industrial and commercial sites. The service sites provide by adapting their consumption on demand is called “Demand Response”.

R3 is currently purchased on monthly basis by the Belgian transmission network operator ELIA, to support the electrical network equilibrium by producing more/consuming less electricity.

Sites therefore commit, on a monthly basis, to reserve a given electrical capacity to R3 and are remunerated for this service. In case of critical grid imbalance, they drop to a given electrical consumption level should ELIA or NextFlex call for it.


To further develop Demand Response participation, ELIA introduced a distinction between R3-Flex and R3-STD. R3-Flex grants sites 8 hours between two requests and a maximum number of request per month; whereas R3-STD does not.

ELIA is working on R3-Flex and R3-STD harmonization, with a first set of updates expected in February 2020. Most impacting changes are:

  • Daily procurement of 6 blocks of 4hours: sites are given the opportunity to accurately define when they are available and for which electrical capacity (previously monthly)
  • Dynamic dimensioning: ELIA will adapt on daily basis the R3 volumes contracted based on the foreseen reserve needs (impacted e.g. by production park and RES availability) (previously yearly)
  • Gradual phase out of R3-Flex: R3-STD minimum contracted volume will gradually increase up to leave no R3-Flex contracted in 2021 (640MW of R3-STD out of 844MW in July 2020 as opposed to 314MW currently).
  • Greater pooling possibility: a given request could be met by a pool of consumption sites and power generators (currently no pooling possibility).

NextFlex solutions

R3-Flex phasing-out should drive sites toward R3-STD, but with risk of continuous 48h requests (i.e. between two procurements periods).

NextFlex is fully aware that sites currently providing R3-Flex are likely unable to deliver unlimited consumption drops. NextFlex currently works closely with ENGIE Electrabel (the largest power producer in Belgium) on asset pooling (generation/consumption) to propose Demand Response offers that meet sites requirements and maximize their R3 revenues.

Please contact us should you be interested in a quote or in more information.

Article réalisé par Pierre Caroff, Business Developer chez NextFlex.

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