Skip to content
TextArray1.87.0
100% local

Solar payback calculator

Work out how many years a solar installation takes to pay for itself, plus its lifetime savings and return.

Input
Output
Related tools
Savings calculatornewNumbers
CAGR calculatornewNumbers
Percentage calculatorNumbers
Birth number validatorNumbers
Inline math evaluatorNumbers
Percent calculatorNumbers
Solar payback calculator
Paste your installation cost, installed capacity, expected annual yield, electricity price and self-consumption share, and this tool works out the payback period in years, the first year's savings, and the total return over the system's lifetime — as both a euro figure and a percentage.
Each line uses the format installation cost;installed kWp;annual yield per kWp;electricity price;self-consumption %, so you can compare several roofs or quotes at once by pasting one scenario per line. The options panel accounts for a subsidy or grant that lowers the net cost, a yearly rise in the electricity price you're avoiding, the slow decline in panel output every system experiences, a feed-in tariff for any energy you export instead of using yourself, ongoing maintenance costs, and a one-off inverter replacement in whichever year you expect it. Pick a currency to label the figures, and switch between a tab-separated table (handy for pasting into a spreadsheet) or a plain-text year-by-year breakdown.
The payback year is interpolated rather than rounded up, so "6.4 years" means the cash flow actually crosses zero partway through year seven — not that it merely started year seven positive. If a scenario never breaks even within the chosen lifetime, the tool says so plainly instead of hiding a negative number in a wall of figures, and every result updates as you type or adjust an option.
All of this runs locally in your browser — none of your cost estimates, quotes or electricity prices are ever uploaded anywhere. Copy the result, download it as a .txt file, or send the output back into the input to refine a scenario further.
FAQ
What format does the input need?
One scenario per line: installation cost;installed kWp;annual yield per kWp;electricity price;self-consumption %. For example, 8000;5;1100;0.20;70 means an €8,000 system, 5 kWp installed, 1,100 kWh produced per kWp per year, €0.20 per kWh, with 70% of the output self-consumed.
How is the payback period calculated?
The tool tracks cumulative cash flow year by year — savings from self-consumed energy plus any feed-in income, minus maintenance and inverter costs — and finds the exact point it crosses zero, interpolated to one decimal place rather than rounded to a whole year.
What happens to energy that is not self-consumed?
It's treated as exported to the grid and valued at the feed-in tariff you set, which defaults to 0. Raise it if your grid operator or supplier pays for exported electricity.
Why does the annual saving change from year to year?
Two options move it in opposite directions: panel output declines slightly each year (degradation), while the electricity price you avoid tends to rise (price growth). The net effect and the running balance are both shown in the year-by-year breakdown.
Is my installation data uploaded anywhere?
No. The whole calculation runs in your browser — your costs, quotes and electricity prices never leave your device.