Daily guide · DK1 · 2026-09-12
What a home battery earned in Denmark West this week, hour by hour
All numbers computed from the week's published auction results at publication and frozen — this article is an honest snapshot, not a page that rewrites itself. Reproduce via the API.
A single 10 kWh battery working one charge-discharge cycle a day earned 12,59 EUR across the week in Denmark West, with the average peak-to-trough spread landing at 204,84 EUR/MWh. The pattern was consistent: cheap windows clustered around midday, most often starting between 12:00 and 14:00, while evening peaks settled at 19:00 or 20:00 on six of the seven days. That midday-to-evening shape is the arbitrage the numbers reward.
The standout is 10 September, when the peak averaged 454,31 EUR/MWh against a cheap window of 74,02 EUR/MWh, delivering 3,35 EUR in a single cycle. That one day accounted for more than a quarter of the weekly total. By contrast, 5 September returned just 0,74 EUR, as its peak reached only 81,94 EUR/MWh. The spread, not the absolute price level, is what pays.
The concrete takeaway: charge in the midday trough and discharge into the 19:00 evening peak, and watch for outlier days like the 10th, which do the heavy lifting. At this rhythm, the modelled annual value comes to 656 EUR at 90 percent round-trip efficiency.
A home battery makes money on one thing: the gap between the day's cheapest and priciest hours. Charge low, discharge across the evening peak instead of buying it, repeat daily. The size of that gap is set every afternoon at the day-ahead auction — so it's measurable, not hypothetical. Here is what one full daily cycle of a 10 kWh battery (at 90% round-trip efficiency — losses included, unlike most brochures) would have captured in DK1 this week.
€12.59
captured this week — one cycle per day, wholesale component, after losses
204.84
€/MWh average cheapest-2h → priciest-2h spread this week
≈€656
a year at this week's spreads — the honest run-rate, not the best-day fantasy
Day by day: the two windows that mattered
| Day | Charge (2h) | at €/MWh | Discharge (2h) | at €/MWh | Cycle value |
|---|---|---|---|---|---|
| 2026-09-05 | 13:00–15:00 | -0.03 | 20:00–22:00 | 81.94 | €0.74 |
| 2026-09-06 | 14:00–16:00 | 0.06 | 19:00–21:00 | 224.76 | €2.02 |
| 2026-09-07 | 13:00–15:00 | 36.99 | 19:00–21:00 | 237.01 | €1.76 |
| 2026-09-08 | 12:00–14:00 | 4.06 | 19:00–21:00 | 251.22 | €2.22 |
| 2026-09-09 | 13:00–15:00 | 63.83 | 07:00–09:00 | 198.35 | €1.15 |
| 2026-09-10 | 12:00–14:00 | 74.02 | 19:00–21:00 | 454.31 | €3.35 |
| 2026-09-11 | 12:00–14:00 | 134.48 | 19:00–21:00 | 299.69 | €1.35 |
Local time, hourly auction means. Days where charging was negative-priced mean you were paid to fill the battery.
Do it automatically
The windows move every day — automation is the whole game. One API call returns a cost-optimal schedule your inverter or energy manager can follow, and there's a full battery simulator to backtest your exact capacity, power and cycle limits against realized prices before you trust it:
curl -X POST -H "Authorization: Bearer YOUR_KEY" \
-H "Content-Type: application/json" \
-d '{"zone": "DK1", "capacity_kwh": 10, "max_power_kw": 5,
"round_trip_efficiency": 0.9, "max_cycles_per_day": 1}' \
https://voltcast.com/api/v1/optimize/batteryHome Assistant users get the schedule as a sensor via the integration. And because the value depends entirely on tomorrow's spread, the P10–P90 forecast — scored publicly every day — tells you whether tomorrow is worth a deep cycle at all.
Method & citation. Prices are hourly means of published day-ahead auction results (native 15-minute periods averaged; ENTSO-E/SMARD, attributed). Wholesale-price component only — grid fees and taxes come on top and vary by supplier. Cite as "Voltcast Research, voltcast.com/guides/battery-arbitrage-dk1-2026-09-12".
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