Solar Payback Calculator
Find how long a solar system takes to pay for itself.
Please note: Estimates for planning only. Actual solar output depends on your latitude, roof orientation, shading, weather and equipment. Get a site-specific assessment and quotes before committing.
What the Solar Payback Calculator does
Payback is the point where accumulated savings equal the net cost after incentives. It is not a simple division, because electricity prices rise while panel output slowly falls — so each year saves a different amount and the crossing point has to be walked year by year.
Formula
Net cost = System cost − IncentivesBlended rate = Import × Self-consumption + Export × (1 − Self-consumption)Year n saving = Generation × (1 − Degradation)^(n−1) × Blended rate × (1 + Inflation)^(n−1) − MaintenancePayback = the year cumulative savings first exceed net cost
Inputs explained
| Input | Unit | Required | Notes |
|---|---|---|---|
| Total system cost | selected currency | Yes | Accepts more than 0. |
| Rebates and tax credits | selected currency | Optional | Accepts 0 or more. |
| Annual generation | kWh | Yes | Accepts more than 0. |
| Import rate per kWh | selected currency | Yes | Accepts more than 0. |
| Export rate per kWh | selected currency | Yes | Accepts 0 or more. |
| Self-consumption share | % | Yes | — |
| Annual electricity price rise | % | Yes | — |
| Annual panel degradation | % | Yes | — |
| Annual maintenance | selected currency | Optional | Accepts 0 or more. |
| Currency | one of 10 options | Optional | — |
How to use it
- Choose Currency.
- Enter Total system cost, Annual generation, Import rate per kWh and Export rate per kWh and 3 more.
- Optionally add Rebates and tax credits and Annual maintenance.
- Select Calculate.
Worked example
A $14,000 system with $4,000 incentives generating 7,884 kWh, 0.28 import, 0.08 export, 40% self-use, 4% inflation.
- Cost
- 14000
- Incentives
- 4000
- Generation
- 7884
- Self-use
- 40
Net cost $10,000, blended rate $0.16/kWh, year 1 saving $1,261 — payback in about 7 years.
Frequently asked questions
What counts as a good payback period?
Under 10 years is strong given a 25-year panel life. Beyond 15 years the case depends heavily on assumptions about future price rises.
Should I include inverter replacement?
Yes, for a realistic figure. Add an annualised allowance to maintenance — a $1,500 inverter at year 13 is roughly $115 a year.