Is a 2h storage system enough for the capacity market?

Yes. 2h is the market standard for storage units; a longer discharge duration raises CAPEX faster than it raises capacity revenue.

When does the unit need to be ready?

The capacity agreement requires the unit to reach readiness to perform the obligation in the delivery year for which the auction was won — we plan the schedule with a 6-month buffer.

Can the capacity market be combined with ancillary services?

Yes, outside threat periods the unit can provide aFRR and mFRR. The EMS prioritizes the capacity obligation over other revenue streams.

Energy storage in the capacity market

BESS in the capacity market — how storage earns from a standby agreement

Short answer

A storage unit enters the capacity market auction with a 2 h (0.5C) configuration, since the capacity obligation is settled against power sustained during a threat period. A new unit can secure a multi-year agreement of up to 17 years.

Capacity agreement as a stable, indexed base revenue stream

2h configuration maximizes revenue per MWh of capacity

Can be stacked with arbitrage and ancillary services

The problem: arbitrage alone doesn't bank a project

Revenue from arbitrage on the power exchange is volatile and hard to contract. A financing bank expects a predictable revenue stream — a capacity agreement provides exactly that, which is why 10–100 MWh projects today are structured around capacity market auctions.

How the capacity obligation works for storage

A unit registers a capacity obligation in MW. During a threat period it must deliver the declared power for the duration of the event. Storage units are subject to an availability correction dependent on discharge duration, which makes a 2h configuration the economic optimum.

Sizing parameters

Project scale → capacity obligation
Capacity	Power	C-rate	Containers
10 MWh	5 MW	0.5C	2
20 MWh	10 MW	0.5C	4
50 MWh	25 MW	0.5C	8–10
100 MWh	50 MW	0.5C	16–20

Cost and payback

A 10 MW / 20 MWh project requires CAPEX of PLN 16–22 million. A capacity agreement typically covers 40–60% of debt service, with arbitrage and ancillary services filling the remainder.

Scope of delivery

20 ft containers with LFP cells and liquid cooling
Grid-forming PCS, unit transformers, MV/HV switchyard
EMS with an interface to the TSO and to the capacity market settlement system
Certification tests and documentation for the general certification process