Size your solar setup correctly
Three free calculators with transparent formulas: panel wattage, battery capacity, and yearly savings. No email, no account.
Step 1
Size the hardware
Start here — how many panel watts you need and what battery capacity to look for based on the appliances you run.
1. Solar system sizing
How many watts of panels you need for your daily consumption, including 25% system losses.
Required panel wattage
770 W
2 kWh / 3.5h sun / 75% efficiency
Recommended battery
3000 Wh
1 days autonomy, 80% DoD, 20% margin
2. Battery capacity calculator
Tick the appliances you want to run and adjust wattage and hours of use.
Estimated daily consumption
1890 Wh
Required battery capacity
2900 Wh
Includes 80% DoD and 20% margin
Step 2
Investment and payback
Once you know what hardware you need, see when the investment pays off and how much you save over 10 years.
3. Yearly savings and payback
Simple estimate: how much of your yearly usage solar covers and when the investment pays off.
Savings per year
188 €
Savings over 10 years
1.875 €
Payback
8.0 years
Methodology and assumptions
Panel wattage = daily consumption (Wh) / peak sun hours / 0.75 (25% system losses: cabling, charge controller, temperature). Battery capacity = daily consumption x days of autonomy x 1.2 (margin) / 0.8 (LiFePO4 depth of discharge). Yearly savings = annual consumption x solar coverage x electricity price. Results are estimates and do not replace an energy audit.
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