The fine print - how it works, what it is and is not:
How the model works This is an hourly scenario calculator. It replays each hour of the past year using measured data and asks: would Estonia have had enough electricity if a generating unit or interconnector failed, demand grew, or new generation were added? The calculator shows logical edge cases; the real market always balances somewhere in between.
The shortfall is covered in this order:
the switched-off generation, or the import possible over the interconnector, is removed, and a data centre's demand is added; transit over the cut interconnector stops - that electricity does not need replacing; added wind, solar or nuclear covers the shortfall, if there is any in that hour; imports from Finland rise over the remaining interconnectors, if they have spare capacity - Nordic hydro and nuclear are usually the cheapest replacement; exports fall: first transit stays in Estonia, then Estonia's own exports are reduced; the remaining oil-shale plants ramp up: Auvere, Eesti and Balti; gas and biomass plants increase output; electricity stored in added batteries is used; Elering's Kiisa emergency reserve power plant (250 MW) starts; if electricity is still lacking, there is a shortfall. When something is added:
added wind, solar or nuclear covers any shortfall; surplus first reduces oil-shale generation; then reduces imports; then increases exports, as far as interconnector capacity allows; any remaining surplus has to be curtailed. If an export interconnector is cut and the electricity is not needed in Estonia, plants turn down - the oil-shale plants first.
The card "Neighbours don't help" changes the neighbours' help:
Finland can't send more: step 4 is skipped, Finland sends the same as it actually did in every hour;Transit can't be cut: in step 5 only Estonia's own exports fall, power passing from Finland to Latvia or from Latvia to Finland keeps flowing. Transit over a cut interconnector (step 2) still stops;Latvia can't send more: always on.This is a simplified order, not the actual bid-based market calculation. In reality the steps happen at the same time. When Estlink 2 was out in 2025, most of the lost import was covered by lower exports to Latvia and about a quarter by oil shale.
A shortfall hour does not mean a nationwide blackout; it means that, according to the model, part of the demand would have to be curtailed in that hour.
Model version 12.
Sources and capacities Plant capacities come from Elering's plant list; installed wind and solar from ENTSO-E as of 1 January 2026.
Source MW Auvere 274 Eesti power plant 700 Balti power plant 185 Shale gas and other 120 Biomass and waste 167 Kiisa emergency reserve 250 Wind 694 Solar 1 231 Estlink 1 350 Estlink 2 650 Latvian lines, in / out 1 250 / 900
"Shale gas and other" is mainly VKG's Põhja CHP plant, which burns gas from shale oil production. Smaller plants are grouped by fuel and cannot be switched off individually. Gas and biomass plants are mostly combined heat and power plants whose output follows heat demand. The model lets them ramp up to full power at any time, summer included, so the real shortfall may be larger than the model shows. Kiisa is Elering's emergency reserve. It does not take part in the electricity market and starts only during faults or shortfalls. In the model it is the last step before a shortfall and cannot be switched off. Data What From Demand Elering Generation and cross-border flows ENTSO-E Day-ahead price Elering Offshore wind ERA5 wind data west of Saaremaa Emission factors EU Emissions Trading System registry, 2025 CO₂ price EEX auctions, January-October 2026
15-minute data are averaged to hours. Gaps of up to three hours are filled linearly. Missing demand is taken from ENTSO-E; a missing oil-shale plant split from the nearest complete hour. Solar output is set to zero in hours when the sun is below the horizon everywhere in Estonia. ENTSO-E and Elering demand differ by a few percent, up to 10% in summer 2026, probably because rooftop solar and batteries are counted differently. In a selected hour's summary the difference is on the row "Demand minus generation". The plants' output is scaled so that it adds up to ENTSO-E's oil-shale total. The plants also burn biomass: Enefit reports 308 GWh of electricity from it in 2025. It is not known how ENTSO-E's figures split it between oil shale and biomass, so switching a plant off may leave some of it in the balance. Wind, solar and existing batteries provide in each hour only what they actually produced. The historical year The model replays the actual hours of one past year. It is not a forecast or a probabilistic security-of-supply assessment. Last year's failures and maintenance are not carried forward. If a plant or interconnector was already out in some hour, switching it off does not change that hour; "GWh lost" counts only hours in which it actually ran. The period consists of whole days and ends eight days before today, because ENTSO-E still corrects recent data during the week. It updates once a day, around midnight. Views In the grid, each column is a day and each row an hour. The boxes show figures for the year; a scenario's change from the actual year appears in smaller type beside the number. Shortfall hours are red in every view.
View What it shows Price Without changes, last year's day-ahead price, darker is higher. With changes, the direction of the price in each hour. Demand Demand in the hour, darker is higher. Affected Hours in which the difference is at least 50 MW. Spare How much more could be taken in the hour: spare plant capacity (including Kiisa), exports that could be stopped and spare room on the Finnish cables. With "Neighbours don't help", room on the Finnish cables and transit don't count. Imports Net imports = imports - transit - Estonia's own exports. Transit enters Estonia and leaves in the same hour. Wind and solar How much of demand wind and solar covered. Emissions CO₂ from Estonian plants, or its cost. Residual load Hours ranked by what is left of demand after wind and solar.
Price Supply falls with switched-off generation and with imports lost over a cut interconnector, including transit. Estonia and Latvia usually have the same price, so electricity Latvia no longer gets counts too. Supply rises with added generation and with electricity that can no longer leave over a cut export line. If both happen in the same hour, the difference decides the direction. Added gas does not lower the price: it runs only when nothing else is enough, and then gas sets the price. Battery discharge increases supply and charging reduces it, except charging from added output that would otherwise be curtailed. An hour without enough electricity counts as pricier: demand can't be met, and the price rises to the market's ceiling. Changes below 50 MW are not shown. No euro price is shown: it cannot be calculated reliably from last year's data. Spare "Switched-off potential" shows how much the switched-off source could have provided over the year: plants at rated capacity, Estlinks at their capacity, the Latvian lines what Latvia actually sent, and wind, solar and batteries what they actually produced. Beside it is how much of that was actually used. Wind and solar Measured wind and solar output counts unless switched off, plus any added capacity. Biomass is not included, because it also includes waste. "Share of demand" counts in each hour only the output up to that hour's demand. The same figure appears in the "Residual load" view. "Fully covered hours" is the share of hours in which wind and solar produced at least as much as was consumed. "Surplus" is output above demand, which has to be exported or curtailed. Emissions Source t CO₂/MWh Auvere 0.85 Eesti power plant 1.82 Balti power plant 1.44 Oil-shale extra output 1.17 Shale gas and other 1.29 Kiisa 0.55 Added gas plant 0.5 Biomass, waste, wind, solar, nuclear 0
The oil-shale factors are each plant's verified 2025 emissions in the EU registry divided by its net output that year. Auvere's factor is lower than the others'. "Oil-shale extra output" is output above what the plant produced in the same hour last year. The shale-gas factor (VKG's Põhja CHP plant) is an upper bound. The model counts biomass and waste as zero. Only Estonian plants count, including production for export. Imported electricity is not counted. "g CO₂ per kWh produced" is the average over all Estonian production: the emissions of all Estonian plants divided by their total output, wind, solar and biomass included. "CO₂ cost" is tonnes times the mean EEX primary auction price (January to October 2026, €78.22/t). Allowances are surrendered for actual emissions by 30 September of the following year, but they can be bought at any time and in advance, so this is not what the producer actually paid. Oil shale's CO₂ cost per megawatt-hour is a price floor: selling below it, a plant loses money on emissions alone. It is about €66 at Auvere, €113 at Balti and €142 at Eesti per MWh. Added capacity Addition Assumption Offshore wind An hourly profile from ERA5 wind data west of Saaremaa and a 15 MW turbine power curve. Over the year it gives 45% of its rating, realistic for offshore wind in the Baltic Sea. Onshore wind, solar The existing fleet's hourly profile per installed megawatt (ENTSO-E 14.1.A, as of 1 January each year). Nuclear 90% of rated capacity every hour - an annual average, not a specific reactor's schedule. Gas plant Runs only when nothing else is enough, after the oil-shale plants. 900 MW is the upper limit of Elering's planned fast-start capacity tender; the tender is technology-neutral, but gas plants are the likely outcome. Batteries A reserve, not traders: they discharge before Kiisa, for two hours at full power. They charge in each day's cheapest hours only from surplus available in that hour (added output that would be curtailed, exports that can be reduced, spare Finnish interconnector capacity, oil shale, gas and biomass), never from Kiisa. Charging and discharging together lose 12%; the state of charge is the same at the start and end of the year. 400 MW is close to Elering's estimate for 2035, 200 MW roughly Hertz 1 and 2. Data centre Extra demand, the same every hour, covered in the order above. 500-1,000 MW is the range raised in the 2026 debate.
Each card starts with a set amount; type your own into its box, up to 5,000 MW.
Added capacity is free in the model: construction and running costs are not counted.
What the model does not account for Failures and maintenance: plants are available every hour; start-up times, fuel limits and UMM notices are not considered.Links between hours: each hour is calculated separately, except the added batteries' charge. Ramp rates and minimum run times are not considered.Estonia's internal grid: Estonia is one node; the Estlinks are taken at rated capacity.Neighbours' situation: Latvia sends no more than it actually did. By default imports from Finland grow within spare capacity and transit can be stopped; the card "Neighbours don't help" turns both off. Whether the neighbours would actually have electricity to give, the model doesn't know.Grid stability: frequency, inertia and reserves work in seconds, the model in hours. Removing the oil-shale plants may affect stability more than the energy balance shows.Flexible demand: demand is fixed.This tool mainly checks whether Estonia would have enough electricity . It is not a model of market bids or of grid stability.
Model versions Version 1 (8 Oct 2026). Since the beta, each model change has been assigned a version number. Every version is checked against the same scenarios; a checksum of their results shows when a number changes. Before that, the model went through 48 iterations (22 Sep-8 Oct 2026).
Version 2 (8 Oct 2026). When data for an oil-shale plant are missing, the estimate no longer overwrites other plants' measured output or exceeds the plant's rated capacity.
Version 3 (11 Oct 2026). The flow chart also shows battery charging. No other figures change.
Version 4 (12 Oct 2026). In the price view, added gas no longer lowers prices: it runs only when other sources are insufficient, and it sets the price in those hours. When all interconnectors are cut, the price is determined by supply in Estonia alone; hours with gas generation now show a higher price rather than no change.
Version 5 (13 Oct 2026). “Switched-off potential” no longer counts wind, solar and batteries as reserves: their potential is what they actually produced. No other figures change.
Version 6 (14 Oct 2026). New views “Wind and solar” and “Emissions”, with the CO₂ cost. Earlier figures do not change.
Version 7 (20 Oct 2026). In the price view, hours without enough electricity count as likely pricier. Before, they were left out.
Version 8 (21 Oct 2026). In the “Affected” view, added generation counts in every hour it produces, not only where it covers what is switched off.
Version 9 (22 Oct 2026). New: data centre, extra demand every hour.
Version 10 (22 Oct 2026). Added offshore wind gives 45% of its rating over the year (was about 53%).
Version 11 (26 Oct 2026). On the Affected tab, added output that covers the data centre's demand no longer counts.
Version 12 (27 Oct 2026). New card "Neighbours don't help": Finland can't send more, and transit can't be cut.