A 10 MW / 20 MWh battery in Germany: one year on our forecast
How much more a typical new grid-scale battery would have earned on the day-ahead market with our forecast than with a plan on yesterday’s prices — 366 days, 7 Nov 2025 – 7 Nov 2026.
This is a simulation on real cleared prices, not a customer’s metered revenue. We chose 10 MW / 20 MWh because it is close to a typical new large battery in Germany: the 83 large-scale systems registered in 2025 add up to 667 MW / 1,244 MWh, about 8 MW / 15 MWh each (ESS News, Jan 2026).
Per year (the 366-day totals scaled to 365 days): +€101,617 more with unlimited cycles, +€79,821 with at most one cycle a day — the same figures the battery calculator shows for 10 MW in Germany.
The battery and the rules
- Battery: 10 MW power, 20 MWh capacity (2 hours), 88 % round-trip efficiency, wear cost €10 per MWh discharged, state of charge 50 % at the start and end of every day.
- Market: day-ahead auction only, Germany–Luxembourg, settled at the actual cleared prices, every quarter-hour. Before grid fees, taxes and trading costs.
- Two plans every day, same battery, same optimiser: (A) planned on our forecast as it would have been made before the 12:00 CET auction; (B) planned on yesterday’s prices at the same local time. A third plan with prices known in advance shows the ceiling.
- Forecasts: walk-forward backtest of the live model. See forecast accuracy in Germany.
Result over the year
| Plan | No cycle limit | Max. 1 cycle a day |
|---|---|---|
| Prices known in advance (ceiling) | €925,987 | €803,302 |
| Our forecast | €838,103 | €732,259 |
| Yesterday’s prices | €736,207 | €652,219 |
| Extra with our forecast | +€101,896 | +€80,040 |
Month by month
| Month | Our forecast | Yesterday’s prices | Extra | Share of best possible |
|---|---|---|---|---|
| Nov 2025 (7–30 Nov, partial) | €25,716 | €19,555 | +€6,162 | 75 % |
| Dec 2025 | €15,458 | €7,789 | +€7,670 | 67 % |
| Jan 2026 | €23,069 | €17,563 | +€5,506 | 71 % |
| Feb 2026 | €20,231 | €11,700 | +€8,531 | 80 % |
| Mar 2026 | €93,129 | €82,832 | +€10,297 | 93 % |
| Apr 2026 | €94,164 | €87,786 | +€6,378 | 93 % |
| May 2026 | €93,138 | €87,657 | +€5,480 | 94 % |
| Jun 2026 | €99,534 | €85,734 | +€13,799 | 94 % |
| Jul 2026 | €79,118 | €74,020 | +€5,098 | 93 % |
| Aug 2026 | €85,742 | €81,849 | +€3,894 | 93 % |
| Sep 2026 | €119,760 | €103,104 | +€16,656 | 94 % |
| Oct 2026 | €79,230 | €67,929 | +€11,301 | 91 % |
| Nov 2026 (1–7 Nov, partial) | €9,814 | €8,691 | +€1,123 | 77 % |
The result follows the market: in Dec 2025 even prices known in advance would have earned only €23,138, in Sep 2026 €127,600.
Where the forecast helped most
| Day | Plan from our forecast | Plan on yesterday’s prices | Difference |
|---|---|---|---|
| 14 Sep 2026 | €8,763 | €3,529 | +€5,233 |
| 3 Dec 2025 | €3,692 | €987 | +€2,705 |
| 21 Sep 2026 | €5,417 | €2,806 | +€2,611 |
| 13 Jun 2026 | €2,445 | €349 | +€2,096 |
| 7 Apr 2026 | €4,677 | €2,664 | +€2,013 |
Where it did worse
On 77 of 366 days the plan on yesterday’s prices earned more. The five worst days:
| Day | Plan from our forecast | Plan on yesterday’s prices | Difference |
|---|---|---|---|
| 20 Jan 2026 | €3,103 | €4,801 | −€1,698 |
| 25 Nov 2025 | €3,639 | €4,350 | −€710 |
| 5 Apr 2026 | €1,266 | €1,879 | −€613 |
| 9 Nov 2025 | −€296 | €192 | −€488 |
| 1 Nov 2026 | −€218 | €225 | −€443 |
Planning on yesterday’s prices lost money on 23 days. The plan from our forecast lost money on 7 days.
What this means for an operator
For a 10 MW / 20 MWh battery the difference between a naive day-ahead plan and a plan on our forecast was about +€101,896 over 366 days. It scales with power: a 1 MW / 2 MWh battery gets about a tenth. The real figure depends on fees, grid charges, how the battery is also used in intraday and balancing markets, and its actual efficiency.
The Battery plan sends this charge and discharge plan for tomorrow every morning before the auction, and the result at actual prices the next day.
Get the same calculation for your battery and zone.
Request a Demo