aFRR (automatic frequency restoration reserve) is currently the most lucrative revenue stream for battery energy storage in Poland. Poland reformed its balancing market on 14 June 2024 and joined the pan-European PICASSO platform on 11 July 2025.

A battery can earn from aFRR in two ways: a capacity fee for holding power in reserve, and a per-MWh payment when PSE activates it.

This article explains the full aFRR market structure, from auction mechanics to qualification rules, based on PSE's balancing rulebook, the Warunki Dotyczące Bilansowania.

Where does aFRR sit in Poland's reserve stack?

PSE procures four frequency reserves, activated in sequence:

• FCR (containment, within 30 seconds)
• aFRR (automatic restoration, full activation within 5 minutes)
• mFRR (manual restoration, around 12 to 15 minutes)
• RR (replacement reserve, around 30 minutes)

aFRR bridges the gap between FCR's fast but limited response and the slower, larger tertiary reserves. Activation is fully automatic, its response window matches how fast a battery can ramp, and a JGM2 unit can split its power between aFRR and wholesale trading day to day. The product resembles aFRR elsewhere in Europe, but Poland's central-dispatch design and its recent move onto PICASSO give it a particular shape.

Poland procures a relatively small amount of aFRR, around 400 to 500 MW in each direction, alongside 197 MW of FCR. That requirement moves through the day and across the seasons, and the combination of a small procured volume and a fast-growing battery fleet is why ancillary revenues are expected to saturate quickly.

The daily and seasonal shape of that requirement suits how a battery operates. Poland's midday solar output pushes day-ahead prices down, often below zero, and a battery can charge cheaply through those hours. As solar falls away into the evening and the system ramps up, upward reserve needs rise, and the energy the battery stored at midday is available to offer back into aFRR up.

aFRR has two halves: capacity and energy

aFRR revenue comes from two markets that clear at different points in time. The first is a national capacity auction, held day-ahead and settled pay-as-cleared at the marginal accepted offer, which pays a battery for holding power in reserve through every contracted hour, whether or not that reserve is ever called, and that is what keeps it the larger and more predictable of the two streams today. The second is the energy market, run through PICASSO, where the volumes PSE actually activates settle at the European marginal price.

A battery can only be activated for energy on the band it already holds in capacity. The energy leg therefore depends on the capacity position rather than forming a market a battery can enter on its own.

aFRR energy tracks the day-ahead price, then spikes

For most periods, aFRR energy prices stay close to the day-ahead curve, so activation adds little to what a battery would earn in the wholesale market.This chart compares the day-ahead price with aFRR up and down activation prices since PICASSO. Most of the time the three sit close together, which limits the extra value from activation, but the exceptions are large: aFRR up occasionally climbs well above the day-ahead level, while aFRR down can fall far below it, at times turning negative so that a battery is paid to charge.

These spikes are rare, occurring in around 1% of periods, but they matter disproportionately. Most hours offer little, yet in the extremes the payoff for a fast, accurate battery is many times a normal day-ahead margin. Across the full period, aFRR up has reached 63,505 PLN/MWh and aFRR down has fallen to -45,862 PLN/MWh.

The chart plots the day-ahead price against aFRR up and down activation prices since PICASSO. For long stretches, all three move together, and in those hours activation is barely worth more than selling the same energy on the wholesale market. The value sits in the tail, where aFRR up can jump well clear of the day-ahead price, and aFRR down can drop below it and turn negative, paying a battery to take energy in.

Those tail events show up in only about 1% of periods, but they carry most of the reason to hold the position. In a normal hour there is little in it, whereas in the extremes a battery can earn several times a day-ahead margin on the same MWh. Over the full post-PICASSO period, aFRR up has reached 63,505 PLN/MWh and aFRR down has fallen as low as -45,862 PLN/MWh.

​​

It pays to charge in aFRR more often than to discharge

The biggest change PICASSO brought is directional, and it shows in how the spread between the day-ahead price and aFRR energy is distributed.