Daily guide · SE3 · 2026-07-17
What a home battery earned in Sweden Stockholm 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 charge-and-discharge cycle in Stockholm returned between 0,44 and 0,66 EUR this week on a 10 kWh battery running at 90% round-trip efficiency. The best days were 12 and 11 July, at 0,66 and 0,65 EUR, both driven by unusually cheap midday windows: charging averaged 4,74 and 9,38 EUR/MWh while evening peaks held near 78,65 and 82,25 EUR/MWh. The weakest returns came on 16 and 14 July, at 0,44 and 0,45 EUR, when cheap-window prices sat above 34 EUR/MWh and compressed the spread.
The pattern is consistent: cheapest power arrived around midday, between 10:00 and 14:00, while peaks clustered in the evening from 20:00 onward. The average spread across the week was 63,44 EUR/MWh. What moved daily earnings was not the peak, which stayed near 100 EUR/MWh, but how low the charging window went.
For the reader, the takeaway is timing over intensity. Charging in the midday trough and holding for the evening peak produced 3,79 EUR across the week, or roughly 198 EUR annualised. Watch the midday floor: that is where the margin is won.
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 SE3 this week.
€3.79
captured this week — one cycle per day, wholesale component, after losses
63.44
€/MWh average cheapest-2h → priciest-2h spread this week
≈€198
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 |
|---|---|---|---|---|---|
| 2026-07-10 | 13:00–15:00 | 37.53 | 20:00–22:00 | 99.68 | €0.52 |
| 2026-07-11 | 14:00–16:00 | 9.38 | 21:00–23:00 | 82.25 | €0.65 |
| 2026-07-12 | 10:00–12:00 | 4.74 | 21:00–23:00 | 78.65 | €0.66 |
| 2026-07-13 | 12:00–14:00 | 41.64 | 20:00–22:00 | 101.68 | €0.5 |
| 2026-07-14 | 13:00–15:00 | 34.45 | 20:00–22:00 | 88.28 | €0.45 |
| 2026-07-15 | 13:00–15:00 | 39.02 | 20:00–22:00 | 106.17 | €0.57 |
| 2026-07-16 | 12:00–14:00 | 44.77 | 22:00–24:00 | 98.87 | €0.44 |
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": "SE3", "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-se3-2026-07-17".
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