Featured image: Transmission pylons illustrate the electricity system batteries can help balance. Contextual photograph; not the Polish project sites. Photo: Matthew Henry / Unsplash. Unsplash licence.
A big battery needs more than cells and a grid connection. Someone must decide when to charge it, when to sell its electricity and how to carry the risk of changing market prices.
On 29 September 2026, Statkraft and Greenvolt announced a ten-year tolling agreement covering two Polish battery projects with combined power capacity of 400 megawatts. Statkraft’s official announcement describes a commercial arrangement for Ełk and Turośń Kościelna. The new development is the contract structure; it is not a newly discovered storage technology.
Power and energy describe different capabilities
Each project is specified at 200 megawatts and 800 megawatt-hours. Together, that is 400 megawatts and 1,600 megawatt-hours, or 1.6 gigawatt-hours, of stated capacity. Project specifications.
Megawatts describe the rate of delivering power. Megawatt-hours describe an amount of energy. Dividing the energy figure by the power figure gives a nominal four-hour duration at that power. The US Energy Information Administration explains this relationship between battery power, energy and duration.
“Four hours” does not mean a battery must always run in one uninterrupted four-hour block. Its operator can use it differently depending on the service being delivered. Nor does nameplate duration answer every question about usable energy, efficiency or performance as equipment ages.
A tolling contract allocates decisions and exposure
Under the announced arrangement, Statkraft obtains the right to decide when the batteries charge and discharge in energy and flexibility markets. Greenvolt receives an additional stream of predictable long-term revenue alongside revenue secured through Poland’s capacity market. The announced division of responsibilities.
In plain language, this places market operation with a company taking on the task of turning flexibility into value. A battery owner does not necessarily have to make every trading decision itself. The contract can separate ownership of a physical asset from the operation of its market rights.
Statkraft describes these arrangements as helping projects obtain greater revenue certainty and supporting financing. That is the commercial rationale, rather than proof that every future operating year will be profitable. The full contract terms are not disclosed in the announcement.
Storage can sell several services
A battery can move energy from one part of the day to another. It can also provide flexibility services that help a power system respond when supply and demand change. The Department of Energy’s storage overview explains why storing energy and releasing it later can help integrate variable generation.
Those services should not be counted as if the same capacity could deliver every one at full output simultaneously. Operators have to work within energy limits, charging requirements and technical obligations. Good operation involves deciding which service to provide and which capacity to reserve.
Statkraft’s background discussion of battery markets addresses the interaction between market opportunities, performance and commercial structures. It is useful context for why a ten-year agreement can matter even without a change in the battery chemistry.
A stronger revenue structure is not a stronger battery cell
Our assessment is that this deal highlights a less visible storage bottleneck: matching physical flexibility with obligations that customers, owners and financiers can understand. A laboratory improvement in cycle life and a contract improvement in revenue certainty solve different problems.
The public announcement does not provide detailed availability guarantees, penalties or the complete risk allocation. It also should not be used as evidence that every part of both installations has completed commissioning. Commercial rights and site operating milestones need to be checked separately.
For the grid, the practical test is whether the contracted assets are available and deliver the services expected of them. For the commercial model, it is whether the parties can sustain those obligations across changing market conditions and equipment performance.
The Polish agreement is significant because it treats market risk as something to allocate deliberately over a decade. Storage deployment depends on that kind of contractual engineering alongside the batteries themselves.
Reporting and source checks completed on 5 October 2026. By FutureTechDose Editor.
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