Average share of the battery's rated capacity tied up in FCAS (raise and lower combined, taking the largest enablement within each direction so overlapping contingency services are not double-counted). This measures how MUCH of the asset is devoted to frequency services. A unit reserving ~35% or more of capacity on average is classified FCAS-Primary — FCAS is its primary use, independent of how much revenue that earns.
FCAS Capacity Reserved is the metric NEMPulse uses to measure how much of a battery is devoted to frequency services, rather than how often. It is the average share of the unit's rated capacity tied up in FCAS across the analysis period, combining raise and lower and taking the largest enablement within each direction so that overlapping contingency services are not double-counted.
This matters because raw FCAS enablement — how many intervals a battery is in any FCAS market at all — saturates near the top: most NEM batteries sit in contingency FCAS almost continuously, so enablement frequency barely distinguishes them. Capacity reserved does distinguish them, because a unit holding a large fraction of its power in reserve for FCAS has correspondingly less available for energy arbitrage. NEMPulse classifies a battery as FCAS-Primary when it reserves roughly 35% or more of its capacity for FCAS on average, independent of how much revenue that ultimately earns.
Related terms: FCASContingency FCASRegulation FCAS
See also: Bidding strategy
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