The acronyms on HNordic's battery income stack are established Nordic electricity markets — not speculative future revenue streams. Each has a published procurement process and contracted clearing prices.
Svenska Kraftnät (SVK), Sweden's transmission system operator, is legally required to maintain grid frequency within ±0.1 Hz of 50 Hz at all times. Renewable generation is weather-dependent and variable; frequency deviates continuously. SVK manages this by procuring frequency-stabilisation capacity from battery operators through competitive daily and weekly tenders. These are the markets that produce the capacity revenue in HNordic's energy income stack. They are established markets with published procurement data — not speculative projections.
FCR-N is the primary frequency stabilisation product. It requires battery operators to modulate output symmetrically — charging when frequency is high, discharging when it is low — within the normal operating band of 49.9 Hz to 50.1 Hz. This happens continuously: the battery is always responding to frequency deviations, not waiting for a call.
SVK procures FCR-N capacity through daily tenders, paying a capacity fee per MW reserved regardless of how much energy the battery actually dispatches. A battery that is physically capable of responding is paid for that capability. The energy dispatched is typically small and symmetric — the battery charges and discharges approximately equally over the course of a day.
FCR-D activates when frequency drops below 49.9 Hz — the threshold that indicates a larger generation loss event (a large power station tripping, a major grid fault). The response requirement is asymmetric: the battery discharges strongly to arrest the frequency decline. FCR-D capacity is procured separately from FCR-N, paid on the same capacity-fee basis. An asset qualified for FCR-D holds a defined MW of capacity reserved for these events.
FCR-D events are less frequent than FCR-N modulation but the activation is more significant — a larger discharge event over a shorter window. Batteries participating in FCR-D must demonstrate sub-second response times, which favours lithium-based battery chemistry.
Where FCR-N and FCR-D contain frequency deviations, aFRR restores frequency to nominal. It activates automatically when frequency deviates beyond FCR tolerance — typically when FCR resources are insufficient on their own. SVK procures aFRR on weekly tenders; activation is continuous in response to a frequency error signal.
aFRR capacity payments per MW are lower than FCR-N in absolute terms, but the products are not alternatives — a battery can hold capacity in multiple products simultaneously (within defined limits), stacking the revenue from each.
mFRR is the largest-volume balancing product in the Nordic market. SVK calls on mFRR reserves manually when FCR and aFRR are insufficient to restore frequency in the required timeframe. mFRR is activated on a slower timescale than FCR or aFRR — typically within 15 minutes — and involves larger energy volumes. The capacity fee per MW is lower than FCR products, but the volume of procurement is substantially larger.
The composition of the balancing market has shifted since 2022. FCR-N prices compressed sharply as new battery capacity entered the market in 2023 and 2024 — too much supply chasing a fixed procurement volume. mFRR volumes have expanded as SVK has adapted procurement to the changing generation mix. A multi-product optimisation strategy that can shift capacity between products in response to market conditions earns materially more than single-product FCR participation alone.
In Great Britain, NESO procures equivalent products under different names:
The revenue architecture is structurally identical to Sweden: capacity fees paid for availability, energy dispatch settled separately, and a multi-product stack that rewards optimisation over single-product participation.
SVK and NESO require assets to be prequalified — technical capability demonstrated, response-time tests passed, aggregation agreements in place. This prequalification is held by HNordic's energy SPV, which participates in these markets across its entire portfolio of battery assets. Individual property batteries are aggregated under this prequalification — their combined MW of capacity is bid into each product's tender.
The property owner receives the contracted energy income from the operating agreement. They do not interact with SVK, NESO, or any aggregator. The AI energy management system manages which portion of the battery's capacity is committed to which market at any given time — balancing frequency-services obligations against day-ahead arbitrage and peak-demand reduction at the property level. The income from all streams flows through HNordic's SPV into the contracted payment to the property owner.
See also: Battery storage: backup power versus revenue asset · The Swedish balancing market versus selling electricity back to the grid · Full FAQ