Europe's Record BESS Tolling Deal: What Statkraft-Greenvolt's 1.6 GWh Means for Storage Finance

On 29 September 2026, Statkraft and Greenvolt Power signed a 10-year battery storage tolling agreement covering 400 MW and 1.6 GWh across two Polish projects — the largest publicly disclosed BESS tolling deal in the European Union to date. The agreement converts what would otherwise be fully merchant battery assets into contracted, forecastable cashflow for a decade, and it sits on top of a separately closed €218 million UniCredit financing package that was committed before the toll was signed.

The Deal: Two Polish Projects, One Tolls

The Statkraft–Greenvolt agreement covers two distinct battery energy storage projects in Poland, totalling 400 MW of power capacity and 1.6 GWh of energy capacity. In a tolling structure, Statkraft pays Greenvolt a fixed fee for the right to use the battery — charging, discharging, and marketing the energy — while Greenvolt retains ownership of the physical asset and responsibility for its availability and performance, as reported by Energy-Storage.news and first disclosed by Discovery Alert.

The financing dimension matters as much as the offtake. The €218 million UniCredit package — split into a €153 million bridge facility and a €65 million guarantee — was committed before the toll was finalised. That sequencing is significant: lenders were willing to underwrite the projects on the strength of the contracted revenue structure, which is precisely the point of tolling. Compare that with a fully merchant BESS, where debt sizing typically requires conservative merchant price forecasts and lower gearing ratios.

The 1.6 GWh figure is what makes this a record. Previous European tolling deals — the UK's Gresham House and Octopus arrangements, for example — have typically covered smaller single-project portfolios. Aggregating two Polish projects into one 10-year toll gives Statkraft the scale to optimise a combined 1.6 GWh of flexibility across a single trading book, while giving Greenvolt a single counterparty and a single contract to present to lenders.

What a Tolling Agreement Actually Is

A tolling agreement is a form of physical offtake in which the tolling counterparty — here, Statkraft — pays a fixed fee per MW of contracted capacity (or per MWh of throughput) for the exclusive right to dispatch the battery. The asset owner keeps operational responsibility: it must maintain the battery within its warranted state of health, deliver availability windows, and meet round-trip efficiency guarantees. In return, it receives a predictable revenue stream that behaves much like a capacity payment.

There are three broad BESS revenue models in the European market, and they sit on a spectrum from risk-free to risk-heavy:

• Tolling agreement — fixed fee, fixed term. The offtaker takes the price risk and captures the trading upside. The owner gets bankable, bond-like cashflow. Used by developers seeking low-cost debt and institutional investors.
• Revenue floor — a minimum guaranteed revenue level (a "floor price") with the owner retaining upside above the floor, often shared with the offtaker. A hybrid structure that trades some upside for partial downside protection.
• Fully merchant — the owner (or a third-party optimiser paid on a fee basis) trades the battery directly in wholesale, balancing, and ancillary markets. Highest expected return, highest volatility, and the hardest to finance with cheap debt.

The trade-off is not abstract. For a battery asset, the difference between a merchant and a tolled cashflow profile is the difference between a 60–65% debt gearing ratio and an 80%+ gearing ratio, industry participants have repeatedly noted — because lenders can discount a contracted floor with a high degree of confidence, but must apply stress scenarios to merchant curves. The lower cost of capital on a tolled asset often compensates for the upside surrendered.

Why Europe Is Moving From Merchant to Tolling

Tolling has moved from niche to mainstream in the European BESS market over 2025 and 2026. As Europe prepares to deploy roughly 200 GWh of battery storage over the next five years, the question every developer faces is not whether to build, but how to finance. Tolling has become one of the answers, as discussed at the Battery Business & Development Forum 2026 and reported by ESS News.

The driver is market saturation of the merchant model. In markets like Great Britain, Germany, and increasingly Poland, wholesale price spreads have compressed as more storage capacity enters service. The "revenue stack" that made 2022–2023 merchant BESS wildly profitable — a combination of frequency response, capacity market payments, and arbitrage — has seen its arbitrage component narrow. When spreads compress, the variance of merchant revenue rises relative to its mean, which is exactly the condition that makes financiers nervous and tolling attractive.

Statkraft's own positioning illustrates the counter-trend. As a large European power trader and originator, it has the trading desk, the analytics, and the balance sheet to absorb price risk and extract value from a 1.6 GWh flexibility portfolio that a single developer could not optimally dispatch. For Greenvolt, the equation is simpler: convert market risk into a 10-year contracted fee, finance at a lower cost of capital, and lock in the return on assets it has built.

Why Poland, and Why Now

Poland is a compelling case study. The Polish grid is among the most coal-dependent in the EU, and the country has been adding solar PV and wind capacity faster than its grid and flexibility markets have adapted. That creates the classic conditions for storage value: large intraday price volatility driven by a rapidly growing solar fleet, a still-lumpy thermal generation stack, and an emerging ancillary services market.

Poland also operates a capacity market that rewards available capacity, and its balancing market is progressively opening to fast-acting storage — both of which underpin the revenue stack a tolling counterparty would exploit. A 4-hour duration battery in Poland can arbitrage the midday solar surplus against the evening peak while also providing secondary reserve, a combination that supports the economics of a 10-year toll.

The choice of 4 hours is not incidental. It is close to the duration that maximises the retained arbitrage value per installed MWh once you account for battery degradation, and it is short enough to keep the per-MW toll fee affordable for the offtaker. As battery cell prices have fallen — into the $45/kWh cell range in 2026, per industry price surveys — the capital cost of installing those additional kWh has dropped enough to make a 4-hour toll competitive with a 2-hour merchant asset on a risk-adjusted basis.

Modeling Tolling Revenue in Energy Optima

For developers evaluating whether to toll, floor, or go merchant, the decisive analysis is the risk-adjusted comparison of 25-year cashflows under each structure. Energy Optima's platform is built for exactly this kind of comparative dispatch and financial modeling:

• EMS dispatch simulation — the dispatch strategies comparison module lets you run the same asset through RULE_BASED, ECONOMIC_DISPATCH, and MILP_HYBRID strategies. For a tolling analysis, the key question is how much merchant upside you are surrendering: run ECONOMIC_DISPATCH on the wholesale price curve, then compare its modelled annual revenue against the toll fee you have been offered.
• 8760-hour arbitrage modeling — hourly charge/discharge optimisation against a full-year price curve, as described in our merchant BESS revenue modeling guide, quantifies the expected spread capture before any contract is signed.
• Battery degradation modeling — a 10-year toll means roughly 3,650 equivalent full cycles. Energy Optima's manufacturer-specific SOH/RTE degradation tables (3D interpolation across year × C-rate × cycles/day) project whether the asset stays above its warranted state-of-health throughout the contract term — the single biggest technical risk the owner retains under a toll.
• Financial projections — the IRR/NPV/LCOE module models contracted toll revenue against merchant scenarios at different discount rates, so you can see precisely how the lower cost of capital on a tolled asset offsets the upside you give up.
• Augmentation planning — augmentation planning with SOH-threshold triggers determines when capacity must be added to hold the toll's availability guarantee, and the replacement CAPEX that flows into the IRR.

The analytical discipline is the same whether the answer is toll, floor, or merchant: build the physical model first, then layer the contract on top and let the numbers decide. A toll is only a good deal if the guaranteed fee exceeds the risk-adjusted present value of the merchant alternative for that specific asset, market, and duration.

What This Signals for 2027

Three takeaways for storage developers and investors:

• Tolling is now the default financing path for merchant-exposed BESS in Europe. The Statkraft–Greenvolt deal, following the UK and Nordic precedent, establishes that a 10-year toll on a multi-hundred-MW portfolio is a financeable structure at scale.
• 4-hour duration is the emerging sweet spot for arbitrage-plus-reserve revenue stacks in markets with high solar penetration and a peaking thermal fleet. Expect more 4-hour, not 2-hour, configurations in EU tenders through 2027.
• Aggregation is the new scale advantage. Bundling two projects into one toll spread across a single trading book is how offtakers like Statkraft extract more value than any single asset could achieve — and it lets owners present a larger, more attractive contract to lenders.

The record is set. The template — contracted offtake, a 4-hour duration, and pre-committed debt — is now proven in Poland, and there is little reason to expect the next record to take long.

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