Free Online Solar Panel Savings Calculator
Estimate solar generation, savings, payback, and CO2 reduction.
Peak sun hours are not daylight hours. They represent the equivalent hours of full-strength sun. A realistic local figure is more useful than a panel's rated output.
Milestones
| Year | Generation | Annual savings | Cumulative savings | Net position |
|---|
Savings are estimates, not a quote. Electricity prices, weather, shading, panel soiling, inverter replacement, and changing tariffs all affect the real return. The CO₂ figure uses a rough 0.386 kg per kWh grid factor and will vary by region.
About the Solar Panel Savings Calculator
A solar proposal usually leads with a payback figure, but the number depends on assumptions that are easy to hide. This calculator makes them visible: system size, peak sun hours, electricity rate, installation cost, incentives, system losses, and annual degradation. Change any one and the payback, lifetime savings, and carbon estimate move. The goal is not to predict the future exactly, but to show which assumptions matter most before you sign a contract.
From kilowatts to kilowatt-hours
A 5 kW system does not produce 5 kWh every hour. Its output depends on the sun, the angle of the panels, shading, temperature, inverter efficiency, and wiring losses. The common shortcut multiplies the system size by peak sun hours and by 365, then applies a loss factor. Peak sun hours are the equivalent number of hours at full standard irradiance, so a location with four peak sun hours receives roughly the same daily energy as four hours of perfect noon sun. The loss field defaults to 15 percent, which covers typical real-world derating.
Payback and lifetime savings
Simple payback divides the net installation cost by the first year's savings. That ignores rising electricity prices, degradation, maintenance, and financing, so the calculator also simulates year by year. Each year's generation is reduced by the degradation rate, and the cumulative savings are compared with the net cost. A system that pays back in eight years under these assumptions has a different risk profile from one that takes eighteen, even if both eventually save money. The lifetime net figure subtracts the net cost from all savings over the chosen period.
Incentives, currency, and carbon
Incentives are entered as a percentage of the installation cost. Real programs may cap the amount, require certification, or arrive as a tax credit rather than a cash rebate, so check the details before treating the net cost as final. Currency selection changes only the formatting; all values are in the same currency. The CO₂ estimate multiplies total generation by a grid emission factor. That factor is a rough average, and a cleaner grid reduces the benefit while a coal-heavy grid increases it.
Frequently asked questions
What are peak sun hours?
Peak sun hours express daily solar energy as the equivalent number of hours at 1,000 watts per square meter. A location with 4.5 peak sun hours receives about 4.5 kWh per square meter per day. It is not the same as the number of daylight hours.
Why does my payback differ from a installer's quote?
Quotes often assume a higher electricity rate, lower losses, no degradation, or a specific incentive. They may also include financing or a tariff that changes over time. Compare the assumptions line by line rather than the headline payback number.
Does the calculator include maintenance and inverter replacement?
No. It focuses on generation, savings, and the net installation cost. Inverter replacement, cleaning, insurance, and financing costs can reduce the lifetime return, especially in the later years of a 25-year analysis.