Solar Panel Payback Calculator
Estimate the annual savings from a solar PV system and how many years it takes to pay for itself. Adjust every input to match your own quote and location.
kWp
kWh/kWp
/kWh
%
/kWh
%/yr
%/yr
years
9.9 years
First-year net saving ≈ 760 · First-year generation ≈ 3,800 kWh · 25-year net ≈ 14,327.5
How it's calculated
The estimate values on-site use and exports separately for every year. It then finds the first point where cumulative net cash flow reaches zero:
year 1 generation = size (kWp) × yield (kWh/kWp)
later generation = year 1 generation × (1 − degradation)^(year − 1)
annual cash flow = self-used kWh × import price + exported kWh × export rate − maintenance
All monetary inputs must use the same local currency. Use a roof-specific annual yield from the European Commission PVGIS tool or an installer proposal. The projection models degradation, price changes and annual maintenance, but excludes financing, discounting, tax and component replacement unless you include them in your inputs.
Accuracy and limitations
- A roof-specific yield is the most important input. Orientation, tilt, shading, temperature, inverter losses and local weather all affect production.
- Self-use should come from interval consumption data when available. Batteries may increase self-use but also add cost, losses and eventual replacement.
- This is an undiscounted cash-flow projection. Add finance, inverter or battery replacement and recurring charges to the cost inputs, or use a professional discounted-cash-flow model for an investment decision.
Frequently asked questions
How is solar payback calculated?
Annual generation (system size × yield per kWp) is split into electricity you use on-site and electricity you export. On-site use is valued at your electricity price and exports at the export rate; the total annual saving is divided into the system cost to give the payback period.
What is "self-use" and why does it matter?
Self-use is the share of generation you consume directly rather than exporting. Because using your own solar avoids buying at the full electricity price — usually far higher than the export rate — a higher self-use fraction shortens payback significantly.
Where can I find annual yield per kWp?
Annual yield depends on location, roof orientation, tilt, shading and system losses. Use a result from the European Commission’s PVGIS tool where supported, or a production estimate from a qualified local installer.
Why does this payback differ from system cost divided by first-year savings?
The calculator builds a cash flow for every year. Generation falls by the degradation rate, imported electricity changes by your annual price assumption, and maintenance is deducted. It then finds the point where cumulative savings recover the installed cost.