Clean Horizon Storage Index (2026)

Clean Horizon’s free monthly Storage Index: the annualised gross revenue of a modelled battery in each of 15 market series (14 countries; Denmark is split into DK1 and DK2), in k€/MW/year. The raw material is the methodology text of the index page (a web clipping, taken 2026-10-02) plus four chart downloads (CSV) for Sweden, Finland, DK1 and DK2, each running January 2023 to August 2026 (44 months) at three battery durations (1h, 2h, 4h). The clipping holds none of the chart values, only each chart’s overall minimum–maximum range; the other eleven markets are therefore not available as data. published is the index launch (January 2025, per the page); the page text was updated afterwards (it describes a January 2026 change).

What the index is

• Monthly annualised gross revenue of a storage asset from the energy, capacity and ancillary-services prices observed that month, calculated with Clean Horizon’s simulation tool COSMOS.
• Model assumptions: 85% round-trip efficiency (at the grid connection point), 1.5 cycles per day, 100% system availability, duration measured on usable AC energy, market-specific prequalification requirements.
• Price knowledge: complete knowledge of day-ahead prices; day-ahead-cleared (D-1) ancillary prices (e.g. FCR, aFRR capacity) “almost completely known”, excluding rare spikes; no knowledge of other markets, whose revenue is estimated statistically from historical prices (e.g. aFRR and mFRR energy).
• Gross revenue: grid fees, taxes and state-of-charge management costs are not deducted.
• Sweden (SE3 zone prices): day-ahead, intraday, FCR-N, FCR-D and mFRR. aFRR is not in the Swedish list. Finland: day-ahead, intraday, FFR, FCR-N, FCR-D, aFRR and mFRR (capacity and energy). DK1: day-ahead, intraday, FCR, aFRR (capacity and energy since October 2024), mFRR capacity. DK2: as DK1 plus FFR and FCR-N/FCR-D.
• Free to use; a paid Premium Index tailors the model to a real project (itemised revenue stack, daily granularity, project-specific constraints).

The January 2026 methodology break

• Before January 2026 the index showed the potential revenue of a marginal MW operating freely on every available market, i.e. the best marginal revenue, even if only a small part of the capacity could earn it.
• From January 2026 it accounts for the actual volumes available in capacity-reservation and energy-activation markets and for the installed storage capacity, so it shows the revenue of the average MW competing with the other projects in the market.
• Other changes the same month: 15-minute optimisation steps (was 1h); intraday revenue added from historical transactions; France’s capacity-mechanism revenue removed; Portugal and Romania added.
• Annualisation changed too: before 2026 a month’s result was multiplied by 12; from 2026 it is divided by the days in the month and multiplied by 365.
• Consequence: the series are not like-for-like across the January 2025/2026 boundary. The clipping does not restate the history on the new method.

What the four series show

Simple arithmetic means of the monthly values, computed for this wiki (not figures Clean Horizon publishes). 2026 is January–August only.

Extremes (1h): Sweden peaked at 1,690 in July 2023 and bottomed at 67 in January 2025; DK2 peaked at 1,752 in July 2023; Finland’s 2026 low is 33 (July). August 2026, the latest month: Sweden 103/138/170, Finland 50/78/111, DK1 253/343/450, DK2 344/471/676 (1h/2h/4h).

The synthesis Nordic Battery Revenue Trends 2023–2026 works through what these series do and do not support.

Reading the numbers with care

• The index is a model output for a reference battery, not realised revenue; it assumes a degree of price foresight and excludes grid fees and taxes (see above).
• From 2026 it shows the average rather than the marginal MW, so in a market where volumes are limited a 2026 value is expected to sit below what the old marginal-MW method would have given. Year-on-year comparisons across January 2026 mix market change and method change.
• The CSVs carry no header beyond the columns Category (month), 1h index, 2h index, 4h index; they are the chart downloads of the same page, as confirmed by the maintainer, and their overall minimum and maximum match the ranges printed in the clipping.
• No revenue split by source is given, so the files cannot show why a month was high or low.

Relevance to wiki topics

• Energy Storage — the only quantitative market-revenue benchmark for batteries in the wiki
• Nordic Battery Revenue Trends 2023–2026 — synthesis built on the four CSVs
• The Swedish BESS Business Case — Revenue Stacking and the FCR Saturation Problem — the Swedish revenue-stacking and FCR-saturation argument this index gives an external time series for
• Fever Energy — Fever’s “twice the Clean Horizon benchmark” claim; see Source - Fever Energy News (2025-2026)
• Balancing Markets — FCR, aFRR and mFRR products referred to in the revenue streams