Daily guide · RO · 2026-08-07
What a home battery earned in Romania 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 10 kWh battery running one cycle a day earned 15,04 EUR across the week in Romania, at 90 percent round-trip efficiency. The average spread between the cheap and peak windows came to 245,50 EUR/MWh. The clear standout was 3 August, when the peak window averaged 412,96 EUR/MWh against a cheap-window average of 63,00 EUR/MWh, delivering 3,09 EUR in a single cycle. The following day, 4 August, was close behind at 3,00 EUR with a peak of 422,39 EUR/MWh.
The weaker days bracket the pattern. On 31 July the cycle returned just 1,49 EUR despite a peak of 259,92 EUR/MWh, because the cheap window still averaged 84,78 EUR/MWh. Where cheap-window prices fell to 2,42 EUR/MWh, as on 2 August, even a moderate peak of 212,69 EUR/MWh produced 1,89 EUR.
The timing was consistent enough to act on: the peak window began at 20:00 on five of seven days, with the cheap window typically opening in the early afternoon. Extended across a full year, this cadence points to 784 EUR. The takeaway: your return depends less on how high the peak runs than on how low the charging window falls.
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 RO this week.
€15.04
captured this week — one cycle per day, wholesale component, after losses
245.5
€/MWh average cheapest-2h → priciest-2h spread this week
≈€784
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 |
|---|---|---|---|---|---|
| 2026-07-31 | 14:00–16:00 | 84.78 | 20:00–22:00 | 259.92 | €1.49 |
| 2026-08-01 | 14:00–16:00 | 15.92 | 19:00–21:00 | 200.42 | €1.64 |
| 2026-08-02 | 12:00–14:00 | 2.42 | 20:00–22:00 | 212.69 | €1.89 |
| 2026-08-03 | 13:00–15:00 | 63 | 20:00–22:00 | 412.96 | €3.09 |
| 2026-08-04 | 14:00–16:00 | 80.26 | 20:00–22:00 | 422.39 | €3 |
| 2026-08-05 | 11:00–13:00 | 73.65 | 20:00–22:00 | 334.03 | €2.27 |
| 2026-08-06 | 11:00–13:00 | 104.77 | 20:00–22:00 | 300.91 | €1.66 |
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": "RO", "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-ro-2026-08-07".
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