Voltonin artikkeleissa käytettyjen termien määritelmät — Viron sähkömarkkinat, säätösähkö- ja tasapalvelut, älykodin joustavuus ja sopimukset, jotka sitovat kaiken yhteen.
An active customer (aktiivne võrguteenuse kasutaja) is, per ELTS § 12¹ (transposing Directive 2019/944 Article 2(8)), a consumer who consumes, stores or sells own-generated electricity, provides flexibility services, or participates in own-generation building energy-efficiency improvements. Active customers carry implicit BRP responsibility for their export volumes and may stack multiple flexibility services at the same metering point.
aFRR is the automatically activated frequency restoration reserve. The Transmission System Operator dispatches it via a closed-loop signal to bring system frequency back to 50 Hz after FCR has contained a deviation. Full activation is required within roughly 5 minutes. Estonia joined the EU PICASSO aFRR-energy platform on 9 April 2025; aFRR capacity is procured jointly with AST and Litgrid via the Baltic BBCM platform from 15 April 2025.
An aggregator is a legal entity that pools the consumption or generation capacity of multiple market participants and offers it to the Transmission System Operator as balancing reserves. Aggregation lets small-scale resources — home batteries, demand response, behind-the-meter solar — qualify for markets whose minimum bid sizes exclude them individually. Volton operates as an aggregator in Estonia.
Area Control Error (ACE) is the second-by-second signal a TSO measures inside its load-frequency-control area to know whether it's over- or under-producing relative to schedule. It combines the deviation between scheduled and actual cross-border interchange with a frequency-bias term proportional to the deviation of system frequency from 50 Hz. ACE drives aFRR (continuously) and mFRR (when sustained); the integral of ACE over a Market Time Unit determines the dominant Direction of System Balancing. Defined in System Operation Guideline (Reg (EU) 2017/1485) Article 3(2)(31).
A balance agreement is the contract between Elering and a BRP under which Elering buys or sells the imbalance energy needed to keep the BRP's portfolio in balance each trading period. Without a balance agreement, no commercial activity on the Estonian wholesale electricity market is possible.
A balance area is the geographic scope within which the TSO settles imbalances against each BRP's schedule. Estonia is a single balance area under Elektrituruseadus and the Konkurentsiamet-approved Bilansi tagamise eeskirjad — every metering point in the country rolls up to one Estonia-wide imbalance settlement under Elering.
A Balance Responsible Party is a market participant that has signed a balance agreement with the Transmission System Operator and accepts financial responsibility for any imbalance between its scheduled and actual electricity consumption or production in each trading period. In Estonia, every retail supplier and every directly-trading large customer must be a BRP or be represented by one.
A market participant certified by the Transmission System Operator to deliver balancing services — typically frequency reserves like FCR, aFRR and mFRR. In Estonia, BSP status is issued by Elering and is the formal precondition for selling balancing energy to the system.
Balancing energy is the electricity the TSO buys or sells in real time to keep system frequency at 50 Hz. Estonian regulation splits the concept into two: Bilansienergia (imbalance energy settled between TSO and BRP) and Reguleerimisenergia (activated balancing energy from BSP bids). EU EBGL collapses both under one label.
A Capacity Calculation Region is a set of bidding-zone borders on which TSOs perform coordinated cross-zonal capacity calculation, established under Article 15 of CACM Regulation (EU) 2015/1222. The Baltic CCR covers the EE–LV, LV–LT, EE–FI (EstLink), LT–SE4 (NordBalt) and LT–PL (LitPol) borders. Capacity calculation uses the coordinated NTC method; operational coordination runs through the Baltic Regional Coordination Centre in Tallinn.
BBCM is the joint day-ahead capacity-procurement platform run by the three Baltic TSOs (Elering, AST, Litgrid). It went live on 4 February 2025 with FCR and mFRR; aFRR was added on 15 April 2025 once Estonia joined PICASSO. Each morning it co-optimises FCR, aFRR and mFRR procurement for next-day delivery — per Elering's reserve-markets Q&A, the Baltic LFC block currently procures 23 MW of FCR per hour, roughly 90–120 MW of aFRR, and 720–860 MW upward / 490–700 MW downward of mFRR. BBCM procures capacity; the energy is activated cross-border through MARI (mFRR) and PICASSO (aFRR).
A grid-connected battery installation that absorbs electricity when prices are low or surplus power is available, and discharges it when needed. In Estonia, BESS projects are built primarily for frequency-reserve revenue (FCR, mFRR) plus spot-arbitrage stacking.
A bidding zone (pakkumispiirkond) is the largest geographic area within which market participants can exchange energy without the cross-border-capacity constraint becoming a price boundary. Estonia is the EE bidding zone — a single nationwide day-ahead clearing price. Cross-border allocation with FI, LV and SE4 is implicit, handled by the SDAC algorithm clearing all coupled zones simultaneously.
The Continental European Synchronous Area is the largest of Europe's synchronous electrical areas — a single 50 Hz alternating-current zone in which all connected systems share frequency in real time. Governed under the System Operation Guideline (Regulation (EU) 2017/1485). The Baltic states desynchronised from BRELL on 8 February 2025 and synchronised with CESA on 9 February 2025.
A Coordinated Balancing Area (CoBA) is a group of TSOs that cooperate on the exchange of balancing services, sharing of reserves and the imbalance-netting process. The Baltic CoBA — Estonia (Elering), Latvia (AST), Lithuania (Litgrid) — runs a joint regulating market and coordinated balance management; the joint Baltic balance settlement model has been operational since January 2018. CoBAs are the cooperation layer below the EU balancing platforms (MARI, PICASSO) and above each TSO's LFC area; the framework is set out in Title V of EBGL Regulation (EU) 2017/2195.
Countertrade is the exchange of electricity between bidding zones initiated by one or more TSOs to bring physical system parameters — typically cross-border power flows — back inside permitted limits while still honouring already-cleared market trades. Defined in CACM Regulation (EU) 2015/1222 Article 2. In Estonia, most cross-border congestion at the Estonia-Finland boundary is resolved through SDAC day-ahead clearing rather than countertrade.
Cross-Border Marginal Price (CBMP) is the marginal balancing-energy price the EU activation platforms (MARI for mFRR, PICASSO for aFRR) publish per direction per area for each Market Time Unit. CBMP is what the cheapest activated bid had to clear at after taking cross-zonal capacity into account; it flows directly into imbalance-price settlement under EBGL Article 55 single pricing. Plus or minus the monthly neutrality component (sign depending on DSB), CBMP equals the realised imbalance reference price for Estonian BRPs.
Cross-Zonal Capacity within Balancing Timeframe (CZCBT) is the share of cross-border transmission capacity that two connected TSOs reserve for the exchange of balancing energy after the day-ahead and intraday markets have used what they need. CZCBT is what makes MARI and PICASSO actually able to clear mFRR and aFRR across borders; methodology set by EBGL Articles 38–39. Without CZCBT, the EU activation platforms would clear inside each LFC area in isolation.
Datahub (Andmevahetusplatvorm Estfeed) is Elering's central electricity-market data exchange. Every retail switching, metering reading, BSP settlement and BRP imbalance flow in Estonia passes through it. Without Datahub access, no commercial activity on the Estonian wholesale or retail electricity market is possible.
The day-ahead market is the wholesale auction that prices each hour of tomorrow's electricity, today. In Estonia the day-ahead market is operated by the NEMO Nord Pool, with hourly auctions for the EE bidding zone clearing alongside Continental Europe under the SDAC mechanism. The clearing price is the spot price reference for nearly every other electricity contract.
DSB is a +1 / 0 / −1 indicator the TSO publishes for each Market Time Unit, signalling whether the Baltic Coordinated Balance Area was in aggregate surplus, balanced, or in aggregate shortage during that interval. Per Elering convention, +1 means BRPs were net long and the TSO downregulated; −1 means BRPs were net short and the TSO upregulated. The sign decides which marginal reference price applies under EBGL Article 55 single pricing and on which side the monthly neutrality component is added.
A Distribution System Operator runs the lower-voltage distribution grid that connects end customers to the transmission backbone — in Estonia, typically 0.4 kV to 35 kV. Elektrilevi, owned by Eesti Energia, serves roughly 87% of Estonian customers across about 95% of the country; smaller regional DSOs cover the rest.
Elering is the Estonian Transmission System Operator, owned 100% by the Republic of Estonia. It operates the high-voltage grid (110 kV+), the cross-border interconnections (Estlink to Finland, 330 kV synchronous to Latvia), and the Datahub through which all retail electricity-market data exchange flows. Elering certifies BSPs and BRPs; without its approval, commercial activity on the wholesale market is impossible.
Emergency reserve capacity is reserve power the TSO holds or pre-orders to handle major contingencies — generator trips beyond design fault, multiple simultaneous outages, sudden cross-border disconnections. It sits outside the normal FCR/aFRR/mFRR market and is activated only when those routine reserves are exhausted. Estonia's flagship emergency reserve is the 250 MW Kiisa peaker plant.
An energy community (energiakogukond) is, per ELTS § 12² (transposing the EU Renewable Energy Community concept from Directive 2018/2001 and the Citizen Energy Community concept from Directive 2019/944), a member-controlled legal entity whose primary purpose is environmental, economic or social benefit rather than profit. Energy communities carry implicit BRP responsibility for their balance, can supply self-produced electricity to members, and rank as active customers when they consume own generation.
ENTSO-E (European Network of Transmission System Operators for Electricity) is the umbrella organisation of European electricity TSOs, based in Brussels, founded 2008. It drafts the EU electricity network codes (EBGL, CACM, SOGL, FCA), operates pan-European balancing platforms (PICASSO, MARI, TERRE, IGCC), and publishes the Transparency Platform — the canonical public data source for European electricity flows. Elering is a full member.
The fastest balancing product on the grid — fully activated within 30 seconds of a frequency deviation, automatic, no TSO command. Every FCR-providing asset carries a local frequency sensor and adjusts output continuously based on what it measures.
A free consumer (vabatarbija) was a pre-2013 ELTS construct that segregated large industrial customers eligible to choose their electricity supplier on the open market from smaller customers stuck with the regulated incumbent. ELTS § 13 was formally repealed on 1 January 2013 with universal market opening; every Estonian consumer is now simply a tarbija (§ 12), with default-supply backstop provided through § 76¹ Üldteenus.
A Financial Transmission Right is a long-dated contract that pays out the price difference between two bidding zones over a delivery period. Estonian traders use FTRs to lock in cross-border spreads — typically Estonia versus Finland, Latvia or Sweden — months or years before delivery. They are the standard way to hedge the risk that one zone’s price will diverge from another’s, and are auctioned by JAO on behalf of the participating TSOs.
Gate closure time is the deadline by which a market participant must submit (or modify) its bid for a given market run. Different markets have different gate closures: day-ahead clears at noon for next-day delivery; intraday keeps an order book open until close to physical delivery; MARI and PICASSO have separate gate closures per Market Time Unit (25 minutes pre-MTU for mFRR Scheduled Activation per EBGL Article 24); BBCM has its own daily gate closure for next-day reserve procurement. Bids changed after gate closure show up in BTD as "unavailable bid volumes".
A Guarantee of Origin (GoO) is an electronic certificate that Elering issues to a generator on application, attesting that one MWh of electricity was produced from a renewable source or in efficient cogeneration. Created under EU Renewable Energy Directive (RED II) Article 19. Estonia joined the AIB cross-border registry in 2014, so Estonian GoOs trade interoperably across Europe.
IGCC is the European platform that runs the imbalance-netting process required by Article 22 of EBGL Regulation (EU) 2017/2195. It offsets opposing aFRR demand between connected LFC areas before any reserves are physically activated, so a positive frequency-restoration need in one area cancels against a negative need in another — saving balancing energy that would otherwise be wasted on activations that net to zero. The Baltic TSOs joined ahead of the 9 February 2025 CESA synchronisation.
The imbalance price is what a Balance Responsible Party pays or receives for any deviation between its scheduled and actual electricity position in each settlement period. Under Article 55 of the Electricity Balancing Guideline (Commission Regulation (EU) 2017/2195), Estonia and the rest of the EU apply single imbalance pricing — one price per direction per 15-minute settlement period, derived from the marginal balancing-energy bids activated through MARI and PICASSO.
The intraday market is the continuous order book that opens after day-ahead gate closure and runs until close to physical delivery — typically 30–60 minutes pre-delivery in Estonia. Where day-ahead clears once at noon, intraday trades constantly to clean up forecast errors before imbalance prices apply.
MARI is the European platform for the cross-border exchange of mFRR balancing energy under Article 20 of EBGL Regulation (EU) 2017/2195. Connected TSOs submit standard mFRR bids into a common merit order list; every 15-minute market time unit the platform clears the cheapest combination of bids needed to meet aggregate mFRR demand, at a marginal price per direction. Elering joined MARI on 9 October 2024.
Market coupling is the European mechanism that runs every day-ahead and intraday auction across the continent as a single matching problem. SDAC (Single Day-Ahead Coupling) handles the noon auction; SIDC (Single Intraday Coupling) handles continuous intraday trading. Instead of each country clearing its bidding zone in isolation, one algorithm takes all bids, all offers and all available cross-border capacities and computes prices for every zone at once. Estonia is fully coupled into both.
The Market Time Unit (MTU) is the smallest time bucket on which European electricity markets clear and settle — every bid, activation, price and imbalance is anchored to one MTU. Across the EU the MTU has been 15 minutes since 1 October 2025 (SDAC migration), reduced from one hour. Estonia's day-ahead, intraday, BBCM, MARI and PICASSO clearings all run on the 15-minute MTU; legacy hourly series remain in the BTD Archive.
mFRR is the manually activated frequency restoration reserve. The Transmission System Operator calls individual bids to release aFRR back to its operating range and to address sustained imbalances. Full delivery is required within 12.5 minutes of activation. mFRR is currently the largest balancing-capacity revenue stream for grid-scale BESS in Estonia.
A microgenerator (mikrotootja) is, per Elering's electricity-market handbook glossary, an electricity consumer who produces electricity primarily for their own use with a generation device of up to 11 kW. The English term "prosumer" is used for the same concept. In Estonia the typical microgenerator is a household with rooftop solar exporting surplus to the grid through the same connection that draws consumption.
A NEMO (Nominated Electricity Market Operator) is, per Regulation (EU) 2019/943 Article 2(8) and CACM Regulation (EU) 2015/1222, an entity designated by the competent authority to perform the tasks of the single day-ahead and single intraday market mechanisms. In Estonia, Nord Pool is the operational NEMO; EPEX SPOT also holds NEMO designation but does not run active trading on EE.
The neutrality component is the per-MWh adjustment a TSO adds to the imbalance price so it neither profits nor loses from balancing operations. It absorbs residual costs — reserve procurement, EU-platform fees, IT, IGCC settlement — that the basic balancing-energy reference price doesn't cover. Article 44 of EBGL Regulation (EU) 2017/2195 makes this financial neutrality legally mandatory for every European TSO. Each Baltic TSO calculates its own component to a methodology approved by the national regulator.
Nord Pool is the Nordic and Baltic electricity exchange operator and Estonia's designated Nominated Electricity Market Operator (NEMO) under CACM Regulation (EU) 2015/1222. It runs the EE bidding-zone day-ahead and intraday auctions and publishes the hourly clearing prices that anchor most Estonian retail tariffs and PPAs.
Net Transfer Capacity (NTC) is the maximum exchange of active power between two bidding zones compatible with operational security, after subtracting a reliability margin from Total Transfer Capacity. CACM Regulation (EU) 2015/1222 calls the broader concept "cross-zonal capacity" and recognises two methodologies — flow-based and coordinated NTC. The Baltic CCR currently uses coordinated NTC for both day-ahead and intraday capacity.
PICASSO is the European platform for the cross-border exchange of aFRR balancing energy under Article 21 of EBGL Regulation (EU) 2017/2195. Its Activation Optimisation Function clears the cross-border aFRR merit order every 4 seconds, producing a marginal price per direction; settlement aggregates into 15-minute market time units. Elering joined PICASSO on 9 April 2025.
Power futures are forward contracts on electricity, traded on financial exchanges (Nasdaq Commodities, EEX) and OTC, that lock in a delivery price for a specific bidding zone and time block weeks to years ahead. They are the principal tool by which generators secure project finance and offtakers hedge electricity-price risk on multi-year horizons. EE-zone liquidity is thin compared to German benchmarks; most Estonian volume settles via EPAD differentials.
A Power Purchase Agreement is a 5–20 year bilateral contract between a renewable generator and a corporate or utility offtaker. The buyer locks in a fixed or indexed power price; the seller secures the long-term revenue needed to finance the project. PPAs were the funding instrument behind most of Europe's renewable build-out from 2020 onwards.
Prequalification is the formal approval gate every prospective Balance Service Provider must pass before bidding any frequency reserve (FCR, aFRR or mFRR) into the Baltic balancing markets. The TSO — Elering in Estonia — checks that the asset (or aggregated portfolio) can technically deliver the service, has the right metering and telemetry, and has signed the standard balancing agreement. The process takes roughly 20 weeks end to end, and qualification has to be renewed every 5 years or whenever the underlying equipment changes.
A trading period (kauplemisperiood) is, per Elering's glossary, the time interval set out in the network code within which a market participant must maintain its balance. It is the basic time unit for imbalance settlement, day-ahead clearing and intraday matching. Estonia historically used a one-hour period; under EBGL Article 53 (Reg (EU) 2017/2195) the EU mandates 15-minute imbalance settlement, with SDAC moving to 15-minute MTU on 1 October 2025.
A Transmission System Operator runs the high-voltage backbone of an electricity grid — typically 110 kV and above — and is responsible for keeping it in second-by-second balance. In Estonia, Elering is the TSO; it operates cross-border interconnections, runs the balancing market and certifies BRPs and BSPs.
Universal service (üldteenus) is, per ELTS § 76¹, every Estonian small consumer's right to buy electricity at a regulated reasonable price from the network operator that connects them. It engages by default whenever a small consumer's open-supply contract lapses without a new one in place. Replaced the pre-2013 müügikohustus and is the statutory backstop that complements the open-market regime.
Up-regulation (ülesreguleerimine) is the TSO's purchase of additional energy from the system when consumption exceeds forecast or generation falls below it. Down-regulation (allareguleerimine) is the opposite — the TSO sells additional energy out when consumption is lower or generation higher than forecast. The price gap between UP and DOWN is what makes mFRR the highest-yielding reserve product for Estonian batteries since 2024.