SpecCalc Hub · Planning estimate
Solar Payback Calculator
Estimate simple solar payback from system cost, incentives, generation, and rates.
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No account required. Calculation history is not stored.
Formula
net_cost = system_cost - incentives annual_savings = self_consumed_kwh * electricity_rate + exported_kwh * export_rate - annual_om_cost simple_payback_years = net_cost / annual_savings
Assumptions
- Inputs are user-provided.
- Results are preliminary estimates.
- Electricity and export rates stay constant.
Limitations
- This is not investment advice and does not model financing, inflation, degradation, or taxes.
Sources / methodology
Simple payback divides net cost by annual savings.
- Formula version
- 1.0.6
- Formula review date
- 2026-05-25
Source links
Quick answer: Solar Payback Calculator estimates net cost from transparent input parameters and a visible formula. Results are informational estimates only and should be checked against the stated assumptions and limitations.
Input parameters
- System cost (currency): 10,000 USD
- Incentives (currency): 1,000 USD
- Annual generation (kWh/year): 7,000 kWh/year
- Self-consumption (%): 80 %
- Electricity rate (/kWh): 0.15 USD/kWh
- Export rate (/kWh): 0.05 USD/kWh
- Annual O&M cost (currency/year): 100 USD/year
- Currency: USD
Output values
- Net cost
- Annual savings
- Simple payback (years)
- Self-consumed (kWh/year)
- Exported (kWh/year)
Step-by-step example
Calculation for the example inputs shown above:
- C₀ = USD 10,000.00 − USD 1,000.00 = USD 9,000.00
- E = 7,000 × 80% = 5,600 kWh/year
- ΔC = 5,600 × USD 0.15 + 1,400 × USD 0.05 − USD 100.00 = USD 810.00
- t = USD 9,000.00 ÷ USD 810.00/year = 11.11 years
Constant annual savings over 20 years are an illustration, not a forecast. Financing, degradation, replacement and taxes are excluded.
Worked examples
Worked example with the form defaults
Example inputs: System cost: 10,000 USD; Incentives: 1,000 USD; Annual generation: 7,000 kWh/year; Self-consumption: 80 %; Electricity rate: 0.15 USD/kWh; Export rate: 0.05 USD/kWh; Annual O&M cost: 100 USD/year; Currency: USD. C₀ = USD 10,000.00 − USD 1,000.00 = USD 9,000.00. E = 7,000 × 80% = 5,600 kWh/year. ΔC = 5,600 × USD 0.15 + 1,400 × USD 0.05 − USD 100.00 = USD 810.00. t = USD 9,000.00 ÷ USD 810.00/year = 11.11 years. Constant annual savings over 20 years are an illustration, not a forecast. Financing, degradation, replacement and taxes are excluded.
Alternative calculation scenario
Example inputs: System cost: 10,000 USD; Incentives: 1,000 USD; Annual generation: 7,000 kWh/year; Self-consumption: 50 %; Electricity rate: 0.15 USD/kWh; Export rate: 0.05 USD/kWh; Annual O&M cost: 100 USD/year; Currency: USD. C₀ = USD 10,000.00 − USD 1,000.00 = USD 9,000.00. E = 7,000 × 50% = 3,500 kWh/year. ΔC = 3,500 × USD 0.15 + 3,500 × USD 0.05 − USD 100.00 = USD 600.00. t = USD 9,000.00 ÷ USD 600.00/year = 15 years. Constant annual savings over 20 years are an illustration, not a forecast. Financing, degradation, replacement and taxes are excluded.
What the result does not establish
The cumulative chart holds annual savings constant. It is not a discounted cash-flow forecast and excludes degradation, financing, replacement and tariff changes unless represented in your inputs.
Common mistakes
- Keep all units consistent with the field labels.
- Check whether the input values are measured, nameplate values or planning assumptions.
- Review the stated assumptions and limitations before using the estimate.
What to check next
Check the inputs, limitations, sources and related calculators before using the estimate in a real decision.
FAQ
What does Solar Payback Calculator calculate?
Solar Payback Calculator estimates net cost from transparent input parameters and a visible formula. Results are informational estimates only and should be checked against the stated assumptions and limitations.
What formula does this calculator use?
The visible formula starts with: net_cost = system_cost - incentives. The full formula, assumptions and limitations are shown on the page.
Are the results stored?
No account is required and SpecCalc Hub does not save personal calculation history.
Related calculators
This calculator provides an estimate for informational purposes only. It is not a certified engineering design, electrical safety approval, or professional installation recommendation. Always verify final decisions with a qualified professional and applicable local codes.