Renewable Energy Payback Calculator
Calculate the payback period, 25-year savings, and ROI for home solar panels or a small wind turbine.
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How to use this calculator
- 1
Select your system type (solar, solar + battery, or wind).
- 2
Enter the installation cost and estimated annual energy generation.
- 3
Set your electricity rate and feed-in tariff rate.
- 4
Estimate what percentage of generated energy you use yourself.
- 5
Add your annual maintenance cost and review the payback period and ROI.
Frequently asked questions
How is the payback period calculated?
This tool uses installation cost ÷ net annual benefit. Net annual benefit = own-use kWh × electricity rate + exported kWh × feed-in rate − annual maintenance. The default inputs give $720 + $160 − $100 = $780 a year and a payback of 10.3 years.
How is generation split between own use and export?
Generation × own-consumption % is treated as used at home and valued at your electricity rate. The rest is exported and valued at the feed-in tariff rate. At 60% of 4,000 kWh, 2,400 kWh is used and 1,600 kWh is exported.
Do system type and system size change the answer?
No. The system-type and system-size fields are not used in the arithmetic. Solar, solar with battery and small wind give identical results when the cost, generation, rates, consumption share and maintenance are the same. Put the system’s real cost and expected generation into the other fields.
How are the 25-year savings and ROI calculated?
25-year savings = net annual benefit × 25 − installation cost, and ROI = that figure ÷ installation cost. The default gives $11,500 and 144%. A negative result is displayed with a minus sign.
What happens if the benefit is zero or negative?
Payback shows N/A, because no number of years recovers the cost. The 25-year line then shows the loss. With no own use, a feed-in rate of $0.02 and a $300 maintenance cost, net benefit is −$220 a year and the 25-year figure −$13,500.
What is left out?
Panel degradation, rising or falling electricity prices, inflation, interest or financing, tax, subsidies, inverter or battery replacement and any change in your own consumption. The model is a flat annual benefit repeated for 25 years.
Where does the CO₂ line come from?
Annual generation × 0.233 kg per kWh, a single figure built into this tool, shown in kilograms. Real grid values vary by country and year, and the line is arithmetic on that figure, not a measured result.
Renewable energy payback calculator: years, 25-year savings and ROI
How to use the renewable energy payback calculator
Use this renewable energy payback calculator to estimate how many years it will take for a solar panel or wind turbine installation to pay for itself through energy savings. Enter the system cost, annual energy output, and local electricity rate above. Results show payback period and lifetime ROI. Free and instant.
How the renewable energy payback calculator works
The renewable energy payback calculator divides the total installed cost by the annual energy savings (output × electricity rate) to compute the simple payback period in years. It also projects cumulative savings over a 25-year lifetime. All calculations run locally in your browser with no data uploaded.
A flat-rate payback model
The calculator values each kilowatt-hour your system generates in one of two ways. Power used at home displaces electricity you would have bought, so it is worth your electricity rate. Power exported is worth the feed-in tariff, which is usually lower. Subtract maintenance, and you have a yearly net benefit. Dividing the installation cost by that benefit gives the simple payback in years.
| Output | Formula |
|---|---|
| Own-use savings | Generation × own-consumption % × electricity rate |
| Feed-in income | Generation × (1 − own-consumption %) × feed-in rate |
| Net annual benefit | Savings + income − maintenance |
| Simple payback | Installation cost ÷ net annual benefit |
| 25-year savings | Net annual benefit × 25 − installation cost |
| ROI | 25-year savings ÷ installation cost |
Worked example: default solar system
An $8,000 installation generating 4,000 kWh a year, with 60% used at home at $0.30 a kWh and the rest exported at $0.10, and $100 a year in maintenance, saves $720 and earns $160. The net benefit is $780, payback is 10.3 years, 25-year savings are $11,500 and the ROI is 144%. Raising own use to 100% lifts the net benefit to $1,100, shortens payback to 7.3 years and lifts 25-year savings to $19,500.
| Own use | Annual savings | Feed-in income | Net benefit | Payback | 25-year savings | ROI |
|---|---|---|---|---|---|---|
| 60% | $720 | $160 | $780 | 10.3 years | $11,500 | 144% |
| 100% | $1,200 | $0 | $1,100 | 7.3 years | $19,500 | 244% |
Worked example: marginal and losing systems
A $12,000 system generating 5,500 kWh, with 40% used at home at $0.20, exports at $0.05 and $150 in maintenance, earns a net benefit of $455 a year. Payback is 26.4 years, which is longer than the 25-year horizon, so the 25-year figure is −$625 and the ROI −5%. Where nothing is used at home, exports earn $0.02 and maintenance is $300, the net benefit is negative at −$220 a year and the payback reads N/A.
| Case | Net benefit | Payback | 25-year savings | ROI |
|---|---|---|---|---|
| $12,000, 5,500 kWh, 40% own use, $0.20 / $0.05 | $455 | 26.4 years | −$625 | −5% |
| $8,000, no own use, $0.02 export, $300 upkeep | −$220 | N/A | −$13,500 | −169% |
What drives the result
The own-consumption share and the gap between the electricity rate and the feed-in rate decide most of the outcome, because they determine what each kWh is worth. Run the calculator with a low and a high own-use percentage to see the range. The system-type and size fields do not enter the formula.
Limits
It is a simple-payback model. It ignores degradation, price changes, financing and replacement costs, so real results will differ. Installers’ quotes and your own bills are better inputs than any default, and the CO₂ line rests on a single factor built into this tool.
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Results are estimates for informational purposes only and do not constitute professional financial, medical, legal, or technical advice. Read full disclaimer →