Case Study: Monitored Installation in Kraków (2024)
Source
Goryl et al., MDPI Energies 2025. 5-minute resolution monitoring data from a real Polish household.
System
| Component | Specification |
|---|---|
| Solar panels | 8 kWp |
| Battery | 10 kWh LiFePO₄ |
| Location | Kraków, Poland |
| Data resolution | 5 minutes |
Annual Performance
| Metric | Value |
|---|---|
| Annual generation | 6,474 kWh |
| Annual consumption | 6,885 kWh |
| Self-consumption without battery | 34% |
| Self-consumption with battery | 56% |
| Battery charged from solar | 1,432 kWh |
| Battery charged from grid (night) | 1,326 kWh |
| Total battery value | €893/year |
Economics
| PV Only | PV + Battery | |
|---|---|---|
| Upfront | €7,970 | €12,910 (with subsidy) |
| Annual savings | €964 | €1,427 |
| Simple payback | 8.3 years | 9.0 years |
| ROI (12 yr, with subsidy) | 38% | 26% |
| ROI (12 yr, no subsidy) | 17% | −3.5% |
Key Finding
With the Mój Prąd subsidy, the battery adds value. Without subsidies, the battery has a negative ROI — the solar-only system outperforms it.
This is consistent with our calculator's message: batteries can make sense in Poland, but only with TOU tariffs (G12) and subsidy support.
Seasonal Reality
| Month | Production | Consumption | Self-Consumption |
|---|---|---|---|
| January | 126 kWh | 991 kWh | 92% |
| May | 937 kWh | 480 kWh | 48% |
| July | 1,024 kWh | 420 kWh | 41% |
| December | 83 kWh | 1,012 kWh | 87% |
Winter: Almost all solar is consumed on-site because production is low relative to demand. Summer: 50–60% of solar is exported unless you have a battery, because production peaks when household demand is lower.
This is a common pattern across Central Europe. A battery helps retain more summer generation for evening use, but the winter gap remains — solar simply doesn't produce enough to meet heating demand in December and January.
Grid Connection
- Single-phase 25A (typical Polish residential)
- Single-phase max solar: 5 kWp
- Export limit per phase: 4.6 kW
- Metering: Net billing (since April 2022)
- Grid connection upgrade: €400–1,800
- Export meter installation: ~€150
What This Means for You
If you're in Poland and considering solar + battery:
- Get the G12 time-of-use tariff first. Without it, the battery spread is too small.
- Check available subsidies. The Mój Prąd program closed in September 2025, but the PME program may reopen.
- Size for your actual consumption. This household consumed 6,885 kWh/year — an 8 kWp system was appropriately sized.
- Expect 8–10 year payback for solar-only, 9–12 years with battery (depending on subsidies).
Read more: Poland Country Guide | Battery Myths | Payback Truth
Last updated: May 2026