How a Giant Battery Pays for Itself: The Żarnowiec Case

Poland is building one of Europe's largest batteries — not for a car, not for a phone, but for the entire electricity grid. Near the Żarnowiec pumped-storage plant on the Baltic coast, PGE Group is installing a 262 MW / 981 MWh battery storage system, built by LG Energy Solution's Wrocław factory, for a contract value of PLN 1.555 billion. Construction started in September 2025, with commissioning planned for the second quarter of 2027.

That's a large number attached to a piece of equipment that, on the surface, does nothing more complicated than store electricity and release it later. So the real question is: how does a project this size actually earn its money back? Working through the answer is a useful way to understand why batteries are quietly becoming one of the most valuable assets on any modern power grid — and why Canadian capital is already positioned inside this market.

The basic idea: buy low, sell high, automatically

At its core, a grid battery does one thing: it stores electricity when it's cheap or abundant, and releases it when it's expensive or scarce. Think of it as a very large, very fast water tank for electricity.

Electricity prices swing more than most people realize. On a sunny, windy day, Poland sometimes produces more renewable power than the grid can use — so much that prices fall to zero or go negative, and wind or solar farms get told to switch off. In the evening, when demand spikes as people get home from work, prices jump again.

A battery captures that gap. It charges during the cheap, oversupplied hours and discharges during the expensive, undersupplied hours. This is called arbitrage, and it's the most intuitive of several ways a battery earns revenue — but it's not the only one, and often not even the largest one.

Where the revenue actually comes from

1. Avoiding wasted renewable energy (curtailment) When there's more wind and solar power than the grid can absorb, operators switch generators off — paying for infrastructure that produces nothing. In the first half of 2025 alone, Poland curtailed around 800 GWh of renewable energy, enough to power roughly 250,000 homes for a year, simply lost. A battery near a wind or solar cluster — and Żarnowiec sits close to PGE's existing onshore wind fleet and its future Baltic Sea offshore wind farms — can absorb that surplus instead of letting it go to waste, turning a loss into stored value.

2. Getting paid to guarantee availability (the capacity market) Poland runs a capacity market: generators and storage assets bid for long-term contracts simply to guarantee they'll be available when the system is under stress, such as a freezing week in January. Żarnowiec has already secured a 17-year capacity market contract for the 2029 delivery year. This is steady, predictable income that doesn't depend on daily price swings — closer to an insurance premium than a trading profit.

3. Keeping the grid stable minute to minute (balancing and ancillary services) Power grids must stay balanced within a very tight band — supply must match demand within seconds, or the system risks instability. Batteries respond almost instantly, far faster than a gas or coal plant, which makes them valuable for split-second correction services. In Poland's reformed balancing market, the available price spread has recently averaged around PLN 695 per MWh, and exceeded PLN 1,000/MWh during spring 2026, when solar oversupply was heaviest. This is currently the single largest revenue source for Polish batteries — larger even than plain price arbitrage.

4. Displacing expensive backup power plants Without storage, grid operators cover evening demand peaks by firing up gas-fired "peaker" plants — units that run only a few hours a day and are expensive to operate. Every MWh a battery delivers instead is a MWh a peaker plant didn't have to burn fuel to produce. At 262 MW for roughly 3.7 hours per full cycle, Żarnowiec can cover a significant evening peak on its own.

Why this adds up to real money

None of these four revenue streams works alone. A well-run battery stacks all of them across a single day: balancing the grid in the morning, absorbing surplus solar at midday, arbitraging the evening price spike, and banking a guaranteed capacity payment in the background all year. Analysts tracking Poland's market have found that batteries there have generated some of the strongest returns in Europe over the past two years, precisely because this stacking is possible.

That's also part of why battery economics have improved so quickly. Global battery pack prices have fallen from roughly $250/kWh a few years ago toward something closer to $115/kWh today. Combine falling equipment costs with rising, more volatile electricity prices, and a project like Żarnowiec starts to make obvious sense — even at a headline price tag of PLN 1.555 billion.

The Canadian angle: same problem, and increasingly the same companies

Ontario is going through its own battery boom for essentially the same reasons — rising demand, a grid with more variable generation, and a search for the fastest way to store power that already exists rather than build brand-new plants:

Oneida BESS (Northland Power, NRStor, and Six Nations of the Grand River): 250 MW / 1,000 MWh.
Napanee Energy Storage (Atura Power and Ameresco), which stores surplus nuclear power generated overnight and releases it during peak demand — the same principle as Żarnowiec storing surplus wind, just a different source of "too much power at the wrong time."
Skyview 2 (Potentia Renewables, e-STORAGE, and the Algonquins of Pikwàkanagàn First Nation): 411 MW, now Canada's largest battery project, expected online in mid-2027 — the same commissioning window as Żarnowiec.
Hagersville (Boralex and Six Nations of the Grand River Development Corporation): 300 MW / 1.2 GWh.
Elora and Hedley (e-STORAGE and Aypa Power): together 420 MW / 2,122 MWh.

What's more interesting than the parallel is that this isn't two markets independently arriving at the same idea — Canadian companies are directly active inside Poland's storage buildout too:

Northland Power, the same Canadian company co-developing Ontario's Oneida BESS, bought 300 MW / 1.2 GWh of battery storage projects in Poland from developer Greenvolt Power in late 2025 — the same order of magnitude as Żarnowiec itself.
Kinterra Capital, a Canadian private equity firm focused on critical minerals and infrastructure, stepped in during 2026 to rescue a €1.63 billion battery materials plant project near Opole after its original developer, US firm Ascend Elements, filed for bankruptcy — acquiring the IP, the site rights, and a €285 million Polish government grant for a fraction of the project's original value. It was Kinterra's first investment in Europe, keeping alive a plant meant to feed the lithium-ion supply chain behind projects like Żarnowiec and reduce Europe's reliance on Asian battery material suppliers.

In other words, the same Canadian capital and expertise building storage in Ontario is now also active in Poland. It's less "Poland and Canada are doing similar things" and more "some of the same players are doing both."

What this means if you're watching from the Canadian side

The headline numbers — PLN 1.555 billion, 262 MW, a 17-year capacity contract — are the easy part to find. What's harder to find, and what actually determines whether a Canadian developer, supplier, or investor can move on an opportunity like this, sits underneath: how capacity market bidding actually works for a foreign entrant, what a storage project needs from PAIH and the local grid operator before it can connect, which of the players already active in Poland (Northland Power, Kinterra) took the direct-investment route versus a partnership route, and why. None of that is a Google search — it's the kind of thing you find out by being in the room, or by talking to someone who already has been.

The bigger picture

Żarnowiec isn't an isolated curiosity — it's a signal of where grids are heading, in Poland, Canada, and everywhere in between. As more wind, solar, and variable demand come online, electricity supply becomes lumpier and less predictable, and the value of something that can absorb a surplus in one hour and release it the next only grows. Batteries don't generate electricity; they make the electricity that already exists worth more, by moving it to the moment it's actually needed.

That, in plain terms, is the whole business case.

Sources: PGE Group construction announcements (September 2025); Energy-Storage.news; ESS-News; Modo Energy Poland balancing market research (2026); Pexapark Poland BESS market analysis (2025); S&P Global energy storage research (2025); IESO Reliability Outlook and Canada Energy Regulator project data (2025–2026); Renewables Now (Northland Power–Poland deal); Notes from Poland; Batteries International; CriticalMB (Kinterra–Ascend Elements–Opole plant); Canada's National Observer; CanREA.