Daily guide · IT-CALA · 2026-08-25
What a home battery earned in Italy Calabria 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.
The pattern this week was consistent even when the returns were not. On every one of the seven days the cheapest window opened in the early afternoon, between 12:00 and 14:00, while the peak settled in the evening, from 19:00 to 22:00. That is the classic solar-driven shape of a summer day in Calabria: midday abundance pushing prices down, then a rise as the sun fades. A single charge-and-discharge cycle on a 10 kWh battery at 90% round-trip efficiency captured an average spread of 108,98 EUR/MWh across the week.
What varied was how much that spread was worth. The strongest day was 23 August, when the cheap window averaged 10,38 EUR/MWh against an evening peak of 223,88 EUR/MWh, delivering 1,91 EUR in cycle value. The weakest was 20 August at just 0,34 EUR, when the afternoon floor held at 153,76 EUR/MWh. Over the full week the battery earned 6,05 EUR.
The takeaway: your returns depend far more on how low the afternoon dips than on the evening peak. Watch the midday floor, not the peak, when deciding whether a cycle is worth it. Annualised, this profile points to roughly 315 EUR.
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 IT-CALA this week.
€6.05
captured this week — one cycle per day, wholesale component, after losses
108.98
€/MWh average cheapest-2h → priciest-2h spread this week
≈€315
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 |
|---|---|---|---|---|---|
| 2026-08-18 | 13:00–15:00 | 135.29 | 20:00–22:00 | 250.3 | €0.9 |
| 2026-08-19 | 13:00–15:00 | 133.27 | 19:00–21:00 | 214.22 | €0.6 |
| 2026-08-20 | 12:00–14:00 | 153.76 | 19:00–21:00 | 208.95 | €0.34 |
| 2026-08-21 | 13:00–15:00 | 151.75 | 19:00–21:00 | 209.39 | €0.37 |
| 2026-08-22 | 14:00–16:00 | 82.38 | 22:00–24:00 | 219.75 | €1.15 |
| 2026-08-23 | 13:00–15:00 | 10.38 | 20:00–22:00 | 223.88 | €1.91 |
| 2026-08-24 | 13:00–15:00 | 149.38 | 19:00–21:00 | 252.61 | €0.78 |
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": "IT-CALA", "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-it-cala-2026-08-25".
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