Balancing capacity

What it is (precise)

Article 2(5) of the Electricity Balancing Guideline (Regulation (EU) 2017/2195, EBGL) defines balancing capacity as 'a volume of reserve capacity that a balancing service provider has agreed to hold and in respect to which the balancing service provider has agreed to submit bids for a corresponding volume of balancing energy to the TSO for the duration of the contract'. The definition welds two promises together: holding the reserve and bidding the energy.

Its counterpart, Article 2(4), defines balancing energy as energy used by TSOs to perform balancing and provided by a balancing service provider — activation is that entry's subject. Elsewhere on this site the pair is compressed to reserve you have agreed to hold and bid versus the energy actually used; the long form above is the law's own wording, from the consolidated text of 19 June 2022, which remains the current version — the guideline's only substantive amendment, Implementing Regulation (EU) 2021/280, left Articles 2, 16, 30 and 32 untouched.

Article 16 turns the definition into an obligation chain. Article 16(4) requires each balancing service provider with a balancing capacity contract to submit balancing energy bids — or integrated scheduling process bids — corresponding to the volume, products and other requirements set out in that contract. Article 16(6) then forbids predetermining the price of those bids in the capacity contract, save a narrow TSO-proposed exemption for specific products under Article 26(3)(b): the award fixes the volume you must offer, and the price stays yours to set on the energy side.

Article 16(5) completes the picture from the other direction, giving every provider that has passed prequalification the right to submit balancing energy bids with no capacity contract at all — the route TSO documents call free bids. A capacity award is therefore one of two doors into balancing energy: the one that pays for availability and binds you to show up.

Why it matters in a real grid-scale project

The commercial shape, in the German framework's own description, is a power-price-based payment for the provision of balancing capacity across all three reserve types, plus — for aFRR and mFRR — an energy-price-based payment for the balancing energy actually used; the capacity remuneration always flows from the TSOs to the providers.

German FCR is the boundary case: only capacity is procured there, and the capacity price covers provision and activation both, with no separate energy payment — the FCR entry carries the product detail. In a storage revenue model this is the reserve-availability line of the stack: income per MW held over a contracted window, whether or not an activation ever comes, sitting alongside arbitrage and, where a market has one, an adequacy product. The revenue stacking entry covers how those lines share one asset.

Direction is part of the product. EBGL Article 32(3) requires upward and downward balancing capacity to be procured separately at least for the frequency restoration and replacement reserves, and Regulation (EU) 2019/943 Article 6(9) repeats the separation, subject to a regulator-approved derogation where that raises economic efficiency. German tenders run positive and negative aFRR and mFRR as separate products, with FCR symmetric, and the German convention maps negative reserve to increasing consumption or reducing generation, positive reserve to the reverse.

For a battery each direction is a state of charge posture held for the whole contracted window: upward reserve means discharge headroom — uncommitted MW and enough energy above the floor to sustain delivery — while downward reserve means footroom, room below the operating window ceiling to absorb the charge. How the scheduler maintains that posture belongs to the state-of-charge and operating-window entries; what matters here is that the capacity fee is the price the TSO pays for you to hold it.

Typical values and standards

EU law constrains how the product is bought without prescribing national mechanics. EBGL Article 32(2) requires the procurement method to be market-based at least for the frequency restoration and replacement reserves, performed on a short-term basis to the extent possible and where economically efficient.

Regulation (EU) 2019/943 Article 6(9) adds the hard timing rule: contracts for balancing capacity shall not be concluded more than one day before the provision of the capacity, and the contracting period shall be no longer than one day, unless the regulatory authority approves earlier or longer contracting.

Even then at least 40% of standard balancing products and a minimum of 30% of all products used for balancing capacity stay on the day-ahead, one-day terms; the remainder runs to a maximum of one month, which Article 6(10) lets the regulator extend, on a request from the TSO and for a limited time, to twelve months.

Procurement itself runs through the connecting TSO under national terms and conditions, which Article 18(1) required the TSOs of each Member State to develop. Article 33 also lets two or more TSOs procure capacity jointly, and the FCR Cooperation auction covers Germany, Austria, Switzerland, France, Belgium and the Netherlands, with further TSOs having joined since — and with Switzerland a member, it is a cross-border TSO cooperation rather than an EU platform.

Germany is the worked example of national granularity — and it is implementation, not European law. FCR, aFRR and mFRR balancing capacity are all tendered daily on the German tender platform regelleistung.net, in six four-hour product slices per day (0-4 h through 20-24 h), with gate closure the day before delivery: 08:00 for FCR, 09:00 for aFRR, 10:00 for mFRR.

Pricing then splits by product. The FCR capacity auction — run jointly through the FCR Cooperation — settles pay-as-cleared: the highest awarded bid sets the price for all, and a country whose import or export limit binds gets its own clearing price.

The aFRR and mFRR capacity auctions settle pay-as-bid, and the award is decided on the capacity price alone — an energy price entered alongside is recorded but ignored in the selection. Two capacity pricing rules therefore coexist in one country, next to marginal pricing on the energy leg (the balancing energy entry's territory), so a sentence about German balancing auctions that names neither the product nor the leg is wrong somewhere.

How it shows up in specs, studies and contracts

In a term sheet or an operating procedure, the award reads as work as well as income. The German implementation of Article 16(4) requires every provider awarded in the capacity market to place balancing energy bids at least in the awarded volume for the same product slice.

The price of those bids remains the provider's own — Article 16(6) keeps it out of the capacity contract, except for certain specific products under Article 26(3)(b), and in Germany contracted energy bids can be re-priced up to the energy market's gate closure — so the capacity fee buys the TSO an option on volume while the activation economics settle later, on the energy side.

For the scheduler an awarded slice pins the plant: the MW sold are unavailable to arbitrage for those four hours, the posture must hold across the whole slice, and the same MW must never be promised to two products in one window.

Non-delivery has a defined price. Under the German TSOs' framework modalities for reserve providers — quoted here from the reading version of 8 December 2022, so check the current consolidation before relying on any exact formula — a breach of holding or delivery obligations lets the connecting TSO reduce the capacity remuneration pro rata by volume and time; for aFRR an incentive component additionally prices the non-held energy against intraday references, and repeated or gross breaches trigger a remediation plan and a twelve-month probation.

Two modelling consequences follow. Build capacity revenue per product, per direction and per slice, from the tender platform's own published results rather than an annual average — and quote the capacity price in the units the platform publishes rather than assuming a convention. Then remember the cost side of the line includes the activations the award obliges you to bid into: their throughput lands on the battery warranty, which is the mFRR entry's warning about capacity-only views of a reserve product.

Common pitfalls

The commonest error in this material is mistaking national implementation for European law. Daily tenders, six four-hour slices and the 08:00/09:00/10:00 gates are German implementation; EU law requires only that procurement be market-based, short-term and — per Regulation 2019/943 Article 6(9) — contracted no more than a day ahead for no longer than a day absent a regulator-approved derogation for earlier or longer contracting, so other Member States lawfully run different granularity.

Great Britain sits outside the EBGL framework altogether post-Brexit: its reserve and response products are procured under a domestic regime, and none of the article numbers on this page govern them.

Superseded designs still circulate. The joint FCR auction ran weekly and pay-as-bid before moving to daily pay-as-cleared auctions, and a single daily FCR product preceded the six four-hour slices — transition steps reported for 2019 and 2020 — so a dataset or article from that era describes a market that no longer exists. Stale secondary sources still call German FCR a weekly auction; the German TSOs' current documents say daily. Date every source before its numbers enter a model.

Finally, the name. Balancing capacity is a reserve product; the similarly named adequacy product is the capacity market entry's subject, and the misconception below draws that boundary. Inside balancing itself, keep capacity and energy on separate model lines with separate prices and separate settlement: the definition in Article 2(5) ties them together by obligation, while the market keeps them apart in payment.