Solar Payback Period Calculator

Solar Payback Period is evaluated from System Cost, Annual Electricity Savings and Federal Tax Credit. The calculation reports Net System Cost, Simple Payback Period and 25-Year Net Savings.

Results

Thanks — we’ve logged this for review.

About the Solar Payback Period Calculator

Solar Payback Period is treated here as a quantitative relation between System Cost, Annual Electricity Savings, Federal Tax Credit and State / Utility Rebate and Net System Cost, Simple Payback Period, 25-Year Net Savings and 25-Year ROI.

The calculator uses a multi formula configuration. Each reported value is read as a direct evaluation of the stored rules with the declared field formats and units.

Formula basis:
Net cost = system cost x (1 - federal credit%) - state rebate
Payback = net cost / annual savings
25-year savings = present value of growing savings stream (inflation-adjusted) - net cost
ROI = net savings / net cost x 100%

Interpret the outputs in the order shown by the result fields. Optional inputs affect only the outputs that depend on those variables.

Formula & How It Works

The calculation applies the following relations exactly as recorded in the metadata:

Net cost = system cost x (1 - federal credit%) - state rebate
Payback = net cost / annual savings
25-year savings = present value of growing savings stream (inflation-adjusted) - net cost
ROI = net savings / net cost x 100%

Each output field is produced by substituting the supplied inputs into the relevant relation and then applying the declared rounding or text format.

Worked Examples

Example 1: Typical US install: $22,000 system, $1,500/yr savings, 30% ITC, $0 rebate, 3% inflation

Inputs

system_cost: 22000 annual_savings: 1500 federal_credit_pct: 30 state_rebate: 0 electricity_inflation: 3
Net System Cost: $15,400. Simple Payback Period: 10.3 years. 25-Year Net Savings: $39,289. 25-Year ROI: 255%

With System Cost = 22,000, Annual Electricity Savings = 1,500, Federal Tax Credit = 30 and State / Utility Rebate = 0 as the stated inputs, the result is Net System Cost = $15,400, Simple Payback Period = 10.3 years and 25-Year Net Savings = $39,289. Each value corresponds to the declared output fields.

Example 2: California incentivized install: $20,000, $2,200/yr savings, 30% ITC, $2,500 SGIP rebate, 4% inflation

Inputs

system_cost: 20000 annual_savings: 2200 federal_credit_pct: 30 state_rebate: 2500 electricity_inflation: 4
Net System Cost: $11,500. Simple Payback Period: 5.2 years. 25-Year Net Savings: $80,121. 25-Year ROI: 697%

With System Cost = 20,000, Annual Electricity Savings = 2,200, Federal Tax Credit = 30 and State / Utility Rebate = 2,500 as the stated inputs, the result is Net System Cost = $11,500, Simple Payback Period = 5.2 years and 25-Year Net Savings = $80,121. Each value corresponds to the declared output fields.

Example 3: Northeast (NY) with state incentives: $18,000, $1,800/yr savings, 30% ITC, $5,000 state credit, 3% inflation

Inputs

system_cost: 18000 annual_savings: 1800 federal_credit_pct: 30 state_rebate: 5000 electricity_inflation: 3
Net System Cost: $7,600. Simple Payback Period: 4.2 years. 25-Year Net Savings: $58,027. 25-Year ROI: 764%

With System Cost = 18,000, Annual Electricity Savings = 1,800, Federal Tax Credit = 30 and State / Utility Rebate = 5,000 as the stated inputs, the result is Net System Cost = $7,600, Simple Payback Period = 4.2 years and 25-Year Net Savings = $58,027. Each value corresponds to the declared output fields.

Example 4: No tax credit scenario (business paid cash, no credit): $25,000, $2,000/yr savings, 0% credit, 3% inflation

Inputs

system_cost: 25000 annual_savings: 2000 federal_credit_pct: 0 state_rebate: 0 electricity_inflation: 3
Net System Cost: $17,500. Simple Payback Period: 8.8 years. 25-Year Net Savings: $55,419. 25-Year ROI: 317%

With System Cost = 25,000, Annual Electricity Savings = 2,000, Federal Tax Credit = 0 and State / Utility Rebate = 0 as the stated inputs, the result is Net System Cost = $17,500, Simple Payback Period = 8.8 years and 25-Year Net Savings = $55,419. Each value corresponds to the declared output fields.

Common Use Cases

  • Calculate solar panel payback period
  • Determine ROI and net lifetime savings from solar
  • Compare solar payback with vs. without tax credits