Daily guide · CZ · 2026-08-19
What a home battery earned in Czechia 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 week split cleanly into two halves. Through 12 to 16 August, a 10 kWh battery charging in the cheap window and discharging into the evening peak earned between 1,54 and 2,43 EUR per cycle, with the standout day on 12 August: a cheap average of 26,16 EUR/MWh against a 299,61 EUR/MWh peak starting at 19:00. The best raw spread came on 15 August, when the midday trough averaged just 2,94 EUR/MWh.
Then the arbitrage collapsed. On 17 and 18 August the cheap window itself averaged 144,74 and 136,27 EUR/MWh, leaving peaks near 215,67 and 203,34 EUR/MWh with barely a gap to exploit. Cycle value fell to 0,49 and 0,47 EUR. When daytime prices stay elevated, there is simply no cheap energy to store, and even a 90 percent round-trip battery has nothing to work with.
The concrete takeaway: total earnings for the week were 10,88 EUR, and the average spread was 179,71 EUR/MWh. At this run rate the yearly figure sits at 567 EUR. Value is concentrated in a handful of wide-spread days, so patience beats forcing daily cycles.
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 CZ this week.
€10.88
captured this week — one cycle per day, wholesale component, after losses
179.71
€/MWh average cheapest-2h → priciest-2h spread this week
≈€567
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 |
|---|---|---|---|---|---|
| 2026-08-12 | 12:00–14:00 | 26.16 | 19:00–21:00 | 299.61 | €2.43 |
| 2026-08-13 | 13:00–15:00 | 66.24 | 19:00–21:00 | 332.73 | €2.33 |
| 2026-08-14 | 13:00–15:00 | 29.6 | 19:00–21:00 | 254.24 | €1.99 |
| 2026-08-15 | 13:00–15:00 | 2.94 | 20:00–22:00 | 184.17 | €1.63 |
| 2026-08-16 | 13:00–15:00 | 31.95 | 21:00–23:00 | 206.11 | €1.54 |
| 2026-08-17 | 14:00–16:00 | 144.74 | 19:00–21:00 | 215.67 | €0.49 |
| 2026-08-18 | 13:00–15:00 | 136.27 | 19:00–21:00 | 203.34 | €0.47 |
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": "CZ", "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-cz-2026-08-19".
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