Help CenterPV Calculations
How outage hours affect system sizing
Calculation3 min readUpdated: 2025-06
Daily outage hours directly determine the battery capacity needed in Backup mode. The longer the outages, the larger the battery must be.
| Outages/day | Battery capacity | Typical scenario |
|---|---|---|
| 0h | Minimal (15 min) | Reliable grid — Europe |
| 4h | Critical load × 4h | Typical urban Africa |
| 8h | Critical load × 8h | Peri-urban areas |
| 12h | Night off-grid equivalent | Connected rural areas |
| 24h | Same as Off-Grid | Unreliable grid |
C_Ah = (P_critical × outage_hours) ÷ (V_sys × DoD)P_critical = critical loads in Wh · outage_hours = outage duration / 24
In Hybrid mode, outages during solar hours don't impact the battery if PV produces enough. Only nighttime outages add to battery autonomy.
Common mistakes
- Underestimating real outage hours by trusting the utility's official announcements
- Sizing the Backup battery on total load instead of critical load only
- Ignoring that outages during solar hours don't affect the battery in Hybrid mode