Solar + Battery Comparison
Compare three options: staying on grid, installing solar panels, or adding a home battery. See which saves the most over 20 years.
Enter Your Values
Using shared profile · 3,500/mo · EUR — edit on Dashboard
Results update automatically as you change values.
What-If Scenarios
Results update instantlyCost Breakdown
20-Year Total Cost Comparison
Click chart to expand
Year 1 Net Energy Cost
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Side-by-Side Comparison
Bars show relative size · ✓ marks the better option- Upfront Cost
- €0
- Self-Consumption
- 0%
- Year 1 Net Energy Cost
- €1,200
- 20-Year Total Cost
- €35,734
- Grid Import/yr
- 4,000 kWh
- Upfront Cost
- €8,000
- Self-Consumption
- 35%
- Year 1 Net Energy Cost
- €126
- 20-Year Total Cost
- €10,135
- Grid Import/yr
- 1,480 kWh
- Upfront Cost
- €13,000
- Self-Consumption
- 70%
- Year 1 Net Energy Cost
- -€66
- 20-Year Total Cost
- €9,418
- Grid Import/yr
- 0 kWh
| Factor | Grid Only | Solar Only | Recommended Solar + Battery |
|---|---|---|---|
| Upfront Cost | €0 | €8,000 | €13,000 |
| Self-Consumption | 0% | 35% | 70% |
| Year 1 Net Energy Cost | €1,200 | €126 | -€66 |
| 20-Year Total Cost | €35,734 | €10,135 | €9,418 |
| Grid Import/yr | 4,000 kWh | 1,480 kWh | 0 kWh |
Solar + Battery is cheapest over 20 years. Solar alone costs €10135 (€8000 install + energy). Adding a €5000 battery raises self-consumption from 35% to 70%, totalling €9418. Grid only: €35734.
Scenario Analysis
How the outcome shifts if your assumptions turn out better or worse than expected.
+20% price
At your stated values
Feed-in drops 50%
Compare Scenarios
Pin up to 3 and see them side by sideSet your inputs, then Pin current to save this scenario. Pin a few variations to compare their scores and outcomes here.
What Moves the Needle Most
How much each factor changes your Grid Only: Total across its full range. Period has the biggest impact.
Focus your attention on Period — getting it right matters most. Factors lower down move the result less, so rough estimates there are fine.
Confidence & Assumptions
The outcome is fairly stable across best and worst cases — this is a robust decision.
Solar Total: €8,947 (worst) → €9,418 (expected) → €8,615 (best)
These are the estimates the result depends on. Adjust them (and the Advanced inputs) to match your real situation — the closer they are to reality, the more reliable your decision.
These estimates are for informational purposes only and do not constitute financial advice. Actual results may vary based on factors not captured in this calculator.
How This Calculator Works
What this calculator does
This three-way comparison shows the total cost of staying on grid electricity, installing solar panels, or adding a home battery to maximise self-consumption.
How the calculation works
For each option we calculate grid import costs minus export credits, plus upfront investment and maintenance. Batteries increase self-consumption, reducing grid imports.
Formula
Grid Cost = Import kWh × Price - Export kWh × Feed-in Self-Use = Production × Self-Consumption % Import = max(Usage - Self-Use, 0)
Sources & defaults
- IEA / national renewable energy agencies
Panel degradation, yield, and lifetime assumptions
- Battery self-consumption uplift models
Higher self-use reduces grid import at retail rates
Example
4,000 kWh/yr, 6kW solar (7,200 kWh/yr): Grid only = €24,000 over 20 years. Solar only (35% self-use) = €12,000. Solar + battery (70% self-use) = €11,500.
How to Use This Calculator
- 1Enter your numbers
Fill in the inputs for Solar + Battery Comparison. Defaults are realistic starting points — replace them with your actual figures.
- 2Understand the calculation
For each option we calculate grid import costs minus export credits, plus upfront investment and maintenance. Batteries increase self-consumption, reducing grid imports.
- 3Review results and scenarios
Check metrics, cost breakdown, comparison tables, and best / expected / worst scenarios. Use sliders to stress-test assumptions.
- 4Decide with the verdict
Read the decision engine recommendation and FAQ. Example: 4,000 kWh/yr, 6kW solar (7,200 kWh/yr): Grid only = €24,000 over 20 years. Solar only (35% self-use) = €12,000. Solar + battery (70% self-use) = €11,500.
Factors to Consider
- Batteries help most when export rates are low
- Self-consumption without battery is typically 30-40%
- With battery, self-consumption can reach 70-80%
- Battery lifespan is 10-15 years — may need replacement
- Solar production may exceed usage in summer
Common Mistakes
- Assuming 100% self-consumption without a battery
- Ignoring declining feed-in tariff rates
- Not accounting for battery replacement cost
- Oversizing solar relative to usage
Frequently Asked Questions
Is a home battery worth it?+
It depends on the gap between import and export rates. If you export at €0.05/kWh but pay €0.30/kWh to import, storing solar for evening use saves €0.25/kWh — batteries often pay back in 8-12 years.
How much battery do I need?+
A 5-10 kWh battery covers typical evening use for a household. Size it to your evening consumption, not total daily use.
Can I add a battery later?+
Yes, most modern solar inverters support retrofit batteries. But installing together may be cheaper than adding later.
This calculator provides estimates for informational purposes only and does not constitute financial, investment, tax, or legal advice. Always consult a qualified professional before making important financial decisions.
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