The best hour by hour stack paid one megawatt €17,621 in October 2025, €7,557 at the low point, and €13,339 in September 2026

The ceiling, month by month

In each hour the megawatt is sold into FCR-N, which covers both directions, or once upward and once downward into the best of the other markets, whichever pays more, and only into a market in which Fingrid bought something that hour. The bar is the month’s sum. It fell from €17,621 in October 2025 to between €7,557 and €13,339 a month since the turn of the year, while Fingrid’s count of batteries went from 1,215 to 2,057 MW.

The grey bar is a part month. A market enters the stack only in an hour in which its price and its volume are both in Fingrid’s files and Fingrid bought something.

Each market on its own

One megawatt sold only into that market, every month, on one scale so the markets can be read against each other. The single figures must not be added: a megawatt cannot be in two markets at once, except one up and one down, which is what the pairs below count.

The markets are filling up

Fingrid buys a roughly steady volume of upward fast reserve each hour, FCR-N, FCR-D up and FFR together, while the batteries able to sell it keep arriving. The line is Fingrid’s installed battery total divided by that upward volume in the same hours: 5.5 megawatts of batteries for every megawatt bought in October 2026, from 4.0 in March 2026. Counting aFRR up and mFRR up as well, which are slower products that other plant also sells, the ratio is 2.5 in the same month.

The ratio as a table

Month	Installed, average MW	Upward reserve bought, average MW	Ratio	Ratio with aFRR and mFRR up
March 2026	1,253	312	4.0	1.8
April 2026	1,274	312	4.1	1.9
May 2026	1,336	357	3.7	1.8
June 2026	1,597	354	4.5	2.0
July 2026	1,614	364	4.4	1.7
August 2026	1,639	338	4.8	1.9
September 2026	1,982	360	5.5	2.6
October 2026 (part)	2,016	364	5.5	2.5

The last twelve months, as a table

Euros for one megawatt, by Finnish month, before any cost. Every month and market as a CSV · the ratio as a CSV.

How each figure is made

Each row of a Fingrid price file has a start, an end and a price in euros per megawatt per hour; the money for one megawatt in that row is the price times the row’s length in hours, put in the month in which it starts, in Finnish time. A row counts only if Fingrid bought some volume in that market in that hour: if it bought nothing, no battery was paid, whatever price is shown, and an hour with no row earns nothing. The pair figures add the up side and the down side, because a battery can hold one megawatt up and one down in the same hour. The ceiling takes, for every hour, the better of FCR-N or the best upward product plus the best downward one. A second calculation written separately checks every figure before it is published.

What is left out

Energy trading on the day-ahead and intraday markets, which batteries of two hours and more depend on, because those prices are Nord Pool’s and may not be shown here. The energy paid when a reserve is used, because what each battery delivers is not published. Fingrid’s yearly FCR contracts, bought at prices not in the open data. Availability, degradation, the optimiser’s share, grid charges and imbalance costs, none of which is taken off. Whether a one-hour battery can offer its whole megawatt to every product under Fingrid’s rules for limited energy reservoirs, which have not been read. So these are the most a megawatt could have been paid, and a real battery earns less.

Source: Fingrid Oyj open data, CC BY 4.0, datasets 317 and 316 (FCR-N price and volume), 318 and 315 (FCR-D up), 283 and 281 (FCR-D down), 277 and 276 (FFR), 52 and 1 (aFRR up), 51 and 2 (aFRR down), 329 and 327 (mFRR up), 330 and 328 (mFRR down), and 424 (installed battery capacity), read 16 October 2026. The figures are calculated by Vitreous from Fingrid’s prices and volumes; Fingrid has not checked them. The method is in the repository as fi/hand/revenue-method.md and the calculation as fi/tools/revenue.py.