Solar Payback Calculator

Estimate simple payback and lifetime savings with editable system-cost, production and electricity assumptions.

System size (kW)

Installed cost before incentives ($)

Incentives entered by user ($)

Annual production per kW (kWh)

Electricity value per kWh ($)

Usable/self-consumed production (%)

Electricity price increase/year (%)

Panel degradation/year (%)

Annual maintenance ($)

Analysis period (years)

Methodology and assumptions

Net cost equals installed cost minus user-entered incentives. Each year’s usable production is valued at the entered electricity rate, adjusted for degradation and rate escalation, less annual maintenance. Simple payback is the first year cumulative savings reach net cost.

Limitations: This is not a site design or quotation. Shading, orientation, weather, time-of-use rates, export compensation, financing, taxes, battery losses and incentive eligibility can materially change results.

For educational estimates only. Results are not financial, tax, engineering or investment advice. Verify important decisions with a qualified professional and current official data.

Methodology reviewed: 1 October 2026

Solar payback assumptions that matter

The calculator values self-consumed or otherwise credited production at the user-entered electricity value, increases that value by the entered escalation rate, reduces production by annual degradation and subtracts maintenance. Payback is the first whole analysis year in which cumulative net savings equal or exceed net installed cost.

Production should be independently verified

Annual kWh per kW varies with location, orientation, tilt, shade, temperature, inverter efficiency, weather and system losses. For a US project, compare your production assumption with NREL PVWatts. For other regions, use a reputable local solar-resource model or an installer’s documented production estimate. Incentives must be entered only after verifying eligibility.

Retail electricity and exported solar can have different values. If your utility pays a lower export credit, use a conservative blended value or separately model self-consumed and exported energy before committing to a purchase.

Primary references: NREL PVWatts and US Department of Energy solar guidance. Rules and incentives change; verify current official information.

Frequently asked questions

Is this a solar quotation?

No. It is a planning estimate and does not model a specific roof, equipment design or utility contract.

Where should annual production come from?

Use a location-specific model such as NREL PVWatts or a documented installer estimate that accounts for roof and system losses.

Should exports use the retail electricity rate?

Only when the applicable utility program credits exports at that value. Otherwise use the verified export rate or a conservative blended value.

Solar Payback Calculator

Methodology and assumptions

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Solar payback assumptions that matter

Production should be independently verified

Frequently asked questions

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