# 254 MW in Brunsbüttel: What Vattenfall's Grid-Scale Battery Really Costs – and What Decides Its Economics

Vattenfall has taken the final investment decision for a large-scale battery storage system in Brunsbüttel: 254 megawatts of power and around 1,000 megawatt-hours of capacity – a four-hour system and one of the largest battery projects in Germany, as well as the largest in Vattenfall's portfolio. The plant will be built on the site of the former Brunsbüttel nuclear power plant, which is currently being decommissioned. A new substation will connect the battery to 50Hertz's 380 kV grid. Commissioning is scheduled for the end of 2028. The symbolism is powerful: a site that stood for nuclear power for decades becomes home to one of the key flexibility technologies of the new energy system. Decommissioning and new construction go hand in hand – and the existing grid connection makes sites like this ideal. ## Why it matters Battery storage is not a nice-to-have; it is an essential component of the energy system of the future. The more wind and solar capacity comes online, the greater the need to balance supply and demand flexibly. Germany's transmission system operators expect more than 80 GW of installed grid-scale battery capacity by 2040. We are only at the beginning of a massive scale-up. With this project, Vattenfall almost doubles its own battery portfolio (currently 270 MW) and aims to market and optimise up to 1,500 MW of third-party storage by 2029. ## But does it pay off? A back-of-the-envelope calculation Vattenfall has not disclosed the investment amount, so I ran the numbers myself – using industry-standard assumptions, explicitly as my own estimate, not a Vattenfall figure. **Assumptions:** - Investment: approx. €300 million (€300/kWh including substation and construction) - Useful life: 20 years - Discount rate (WACC): 6% - Operating costs: 1.5% of investment per year (approx. €4.5 million), escalating 2% annually - Cell replacement/augmentation in year 10: 20% of investment (€60 million) - Degradation: 2.5% capacity loss per year - Utilisation: 1 full cycle per day, 350 days per year - Residual value after 20 years: 10% of investment (grid connection, site, recycling) **Result of the discounted cash flow analysis:** | Item | Present value | |---|---| | Investment | €300 million | | Operating costs (20 years) | +€60 million | | Augmentation year 10 | +€34 million | | Residual value year 20 | −€9 million | | **Total cost (present value)** | **approx. €385 million** | Around 6 TWh is discharged over 20 years, or roughly 3.6 billion kWh on a discounted basis. This yields a **levelized cost of storage of around 10.6 cents per discharged kilowatt-hour**. Of that, about 8.3 cents is investment, 1.7 cents operations and 0.9 cents augmentation; the residual value reduces it by 0.3 cents. On top of this come charging losses: at a round-trip efficiency of 85–88%, a good 1.15 kWh must be purchased for every kWh discharged. ## The sensitivities that matter The 10.6 cents is not a fixed value but the outcome of a handful of levers. Three of them dominate: **1. Utilisation – by far the biggest lever.** At 1.5 cycles per day the cost drops to around 7 cents/kWh, at 2 cycles to just over 5 cents. Anyone using the battery purely for arbitrage between midday solar and the evening peak is running it expensively. Anyone stacking intraday trading, ancillary services and redispatch (“revenue stacking”) brings the cost down fast. This is exactly why Vattenfall is building up its optimisation business for third-party storage in parallel – trading and dispatch is the real value driver. **2. Investment cost.** Every €50 million up or down shifts the LCOS by roughly 1.7 cents. At €250 million the figure is 8.8 cents, at €350 million it is 12.3 cents. Cell prices keep falling – whoever takes the investment decision today benefits only from current price levels; whoever orders in 2027 will probably get a better deal. **3. Cost of capital.** Between 5% and 8% WACC there is a gap of about 2 cents/kWh at a €300 million investment (9.9 vs. 11.9 cents). Storage is capital-intensive; cheap financing and a reliable regulatory framework are therefore not a side issue but a core part of the business case. Comparatively uncritical are operating costs (around 1.7 cents; even at 2% OPEX barely more than 2.3 cents) and residual value (10.8 instead of 10.6 cents without it – discounting over 20 years eats it almost entirely). | Investment \ WACC | 5% | 6% | 8% | |---|---|---|---| | €250 million | 8.3 ct | 8.8 ct | 9.9 ct | | €300 million | 9.9 ct | 10.6 ct | 11.9 ct | | €350 million | 11.6 ct | 12.3 ct | 13.9 ct | *(1 cycle/day in each case)* ## Conclusion To cover capital and operating costs, Vattenfall must earn an average margin of well over 10 cents per kilowatt-hour traded. With daily spreads of 8–15 cents on windy days, that is tight with pure arbitrage – but well achievable with stacked revenues and more than one cycle per day. And the more renewables enter the grid, the wider the spreads become. Above all, the calculation shows one thing: storage is a scale and utilisation business. Technology is not the deciding factor – financing, site selection with an existing grid connection and the ability to market the battery intelligently are. Brunsbüttel brings two of the three by default. Projects like this need to scale fast if the energy transition is to succeed. Congratulations to Vattenfall on this decision – hopefully a model for many more power plant sites. --- *All cost figures are my own estimates based on industry benchmarks. Vattenfall has not published an investment amount.*