​On 3 November, the German regulator BNetzA announced the winners of the first long-duration capacity auctions - with 5.1 GW of gas, including lignite retrofits, winning contracts, but no batteries.

But batteries are expected to sweep some of the future auctions under the StromVKG. The first capacity auctions where batteries can compete will take place in 2027 for delivery from 2031. The generation auction on 18 May procures 2 GW of de-rated new-build capacity. The capacity auction on 1 December is likely larger and open to existing assets, so competition is stiffer, and most contracts will likely be one-year. Both pay per de-rated megawatt: the share of a battery's power the regulator expects to be available when the system runs short.

That share decides how much of a battery's nameplate earns a capacity payment. The regulator BNetzA will publish it at least 13 weeks before each auction, by mid-February 2027 for May and by 1 September for December. But units have to prequalify before then - with a January deadline for the May auction - without knowing the exact de-rating factors.

The StromVKG already contains the formulas allowed to calculate it. What it lacks is the data, which comes from BNetzA's own supply-security model. We ran the formula on its European equivalent, ENTSO-E's European Resource Adequacy Assessment (ERAA). On ERAA 2025, a 4-hour battery would be credited at 34-39% in the December auction, and a 2-hour battery at about 20%. BNetzA’s own model will use different assumptions, so the published factors will differ. But the driver, multi-day winter shortfalls, is structural, so we expect factors to land well below Belgium and Italy.

Key takeaways

• Under the published formula, Germany's de-rating factors are among Europe's strictest, cutting a 4-hour battery to around a third of its nameplate capacity. That is 34-39% in the December auction and 27-30% in May, well below the 51-57% Belgium and northern Italy publish.
• Even existing batteries may qualify for longer contracts if they hit a minimum spending requirement. Extending a battery’s duration doesn’t count towards the investment needed, but adding around 10–20% more power does, if the grid connection allows it.
• De-rating factors are likely to fall further. As coal retires, a 4-hour battery drops to 26-29% by 2035. ERAA already assumes 17 GW of new gas by 2033, more than the 9 GW the long-duration auctions will procure, so the StromVKG gas build is unlikely to lift battery de-rating factors.

A 4-hour battery should be credited at 27-30% in the May auction, and 34-39% in the December one

The two auctions apply different de-rating factors. December uses the factor for the 2031/32 delivery year for all contract lengths and keeps it for the whole contract, as the law expects most contracts to be one-year only. The new-build auction in May only offers 15-year contracts, so the de-rating factor is averaged over all 15 contract years.

Using the ERAA 2025 dataset, that gives a 4-hour battery 34-39% in December and 27-30% in May. A 2-hour battery gets about 20% in December. This is based on a simplified formula which is only applicable to the 2027 auctions, but in line with other methodologies across Europe which show that these results are close to the expected results of the full BNetzA report.

The two auctions call for different bidding strategies

The two auctions differ not only in de-rating factors. Different sizes and competition rules make them differ more widely in character and strategy: