How solar payback is estimated
The calculator subtracts incentives and rebates from the system cost, then compares that net cost with estimated electricity-bill savings. First-year savings are annual solar output multiplied by your electricity price. If you expect electricity prices to rise, the estimate increases future annual savings by that rate.
Getting better inputs
Use an installer’s production estimate for annual output and your utility bill for the electricity price. The best result comes from a quote that reflects your roof, shade, orientation, utility tariff, and local net-metering or export rules.
What can change the result
Financing, taxes, panel degradation, maintenance, battery costs, export rates, and roof repairs can materially change solar economics. Incentives also vary by location and can change over time. This tool is a first estimate, not a purchase recommendation.
Simple payback is not the whole decision
A shorter payback period can be attractive, but it is not the only measure. Consider the expected system life, resilience needs, the condition of the roof, and whether the assumptions still make sense if electricity prices or household use change.
Questions for an installer
Ask how annual production was estimated, which incentives are included, what export rate applies, whether a roof replacement is likely during the system life, and what happens if your electricity use changes. Compare quotes on the same assumptions.