Use cases
Worldwide solar calculator for monthly production, self-consumption, surplus, savings and payback, with a chart and practical recommendations.
Practical example
- 01
Prepare questions before requesting quotes.
- 02
Compare system sizes and battery options.
- 03
Plan EV charging, water heating and flexible loads during solar hours.
From kWh to savings: three scenarios
Reproduce A with the initial inputs. B adds a 5 kWh battery costing €3,000; C keeps A but receives no payment for exports. These are teaching assumptions, not quotes or current tariffs.
Local climate: Sunny · EUR
| Your inputs | A | B | C |
|---|---|---|---|
| Latitude (°) | 37.8882 | 37.8882 | 37.8882 |
| Maximum installed power (kWp) | 4.5 | 4.5 | 4.5 |
| Average monthly consumption (kWh) | 350 | 350 | 350 |
| Installed battery capacity (kWh) | 0 | 5 | 0 |
| Total installation cost without battery (€) | 6,500 | 6,500 | 6,500 |
| Total battery installation cost (€) | 0 | 3,000 | 0 |
| Electricity purchase price (€/kWh) | 0.22 | 0.22 | 0.22 |
| Surplus buyback price (€/kWh) | 0.06 | 0.06 | 0 |
| Contracted power (kW) | 4.6 | 4.6 | 4.6 |
| Fixed power charge (€/kW/month) | 3.2 | 3.2 | 3.2 |
| Annual production / Estimated annual savings | A | B | C |
|---|---|---|---|
| Annual production (kWh) | 6,976.4 | 6,976.4 | 6,976.4 |
| Self-consumed energy (kWh) | 1,764 | 3,078 | 1,764 |
| Exported surplus (kWh) | 5,212.4 | 3,719.22 | 5,212.4 |
| Battery losses (kWh) | 0 | 179.18 | 0 |
| Grid import (kWh) | 2,436 | 1,122 | 2,436 |
| Consumption covered (%) | 42 | 73.29 | 42 |
| Annual fixed power charge (€) | 176.64 | 176.64 | 176.64 |
| Estimated annual savings (€) | 700.82 | 900.31 | 388.08 |
| Simple payback (years) | 9.3 | 10.6 | 16.7 |
6,976 kWh
Annual production
1,764 kWh
Self-consumed energy
5,212 kWh
Exported surplus
A · Estimated annual savings: 1,764 × 0.22 + 5,212.4 × 0.06 ≈ 700.82 €
Yield is interpolated in an editorial latitude table and multiplied by a climate factor. It does not query PVGIS or weather and does not know your roof shading. Direct use is capped at 42% of monthly consumption; the battery assumes 88% efficiency and a daily limit of 72% of capacity.
Savings combine self-use at the purchase price and exports at the sale price. No compensation caps apply. Fixed charges remain; simple payback excludes finance, taxes, maintenance, degradation and replacements. Check the contract and an hourly simulation before deciding.
Responsible scope
Sources and scope
This is a guidance estimate by latitude and climate band, not a quote or engineering study. It does not know the exact roof geometry, shading or weather.