Solar Panel ROI & Payback Calculator
Detailed solar financial analysis with year-by-year cash flow, payback period, IRR, and NPV. Compare cash vs loan financing options.
Cumulative Net Savings
Year-by-Year Cash Flow
| Year | Rate (cents/kWh) | Production (kWh) | Savings | Cumulative Savings | Cumulative Net |
|---|---|---|---|---|---|
| 1 | 15.0c | 10,000 | $1,500 | $1,500 | -$13,200 |
| 2 | 15.4c | 9,950 | $1,537 | $3,037 | -$11,663 |
| 3 | 15.9c | 9,900 | $1,575 | $4,612 | -$10,088 |
| 4 | 16.4c | 9,851 | $1,615 | $6,227 | -$8,473 |
| 5 | 16.9c | 9,801 | $1,655 | $7,882 | -$6,818 |
| 6 | 17.4c | 9,752 | $1,696 | $9,578 | -$5,122 |
| 7 | 17.9c | 9,704 | $1,738 | $11,316 | -$3,384 |
| 8 | 18.4c | 9,655 | $1,781 | $13,097 | -$1,603 |
| 9 | 19.0c | 9,607 | $1,825 | $14,922 | $222 |
| 10 | 19.6c | 9,559 | $1,871 | $16,793 | $2,093 |
| 11 | 20.2c | 9,511 | $1,917 | $18,710 | $4,010 |
| 12 | 20.8c | 9,464 | $1,965 | $20,675 | $5,975 |
| 13 | 21.4c | 9,416 | $2,014 | $22,689 | $7,989 |
| 14 | 22.0c | 9,369 | $2,064 | $24,753 | $10,053 |
| 15 | 22.7c | 9,322 | $2,115 | $26,868 | $12,168 |
| 16 | 23.4c | 9,276 | $2,168 | $29,036 | $14,336 |
| 17 | 24.1c | 9,229 | $2,221 | $31,257 | $16,557 |
| 18 | 24.8c | 9,183 | $2,277 | $33,534 | $18,834 |
| 19 | 25.5c | 9,137 | $2,333 | $35,867 | $21,167 |
| 20 | 26.3c | 9,092 | $2,391 | $38,258 | $23,558 |
| 21 | 27.1c | 9,046 | $2,451 | $40,709 | $26,009 |
| 22 | 27.9c | 9,001 | $2,512 | $43,221 | $28,521 |
| 23 | 28.7c | 8,956 | $2,574 | $45,795 | $31,095 |
| 24 | 29.6c | 8,911 | $2,638 | $48,433 | $33,733 |
| 25 | 30.5c | 8,867 | $2,704 | $51,137 | $36,437 |
How It Works
This calculator performs a detailed 25-year financial analysis of your solar investment. It models annual electricity savings with rising utility rates and 0.5%/year panel degradation.
For cash purchases: Net cost = System Cost - Federal ITC (30%) - State Incentives. The cumulative net column shows when your total savings exceed the net cost (break-even).
For loan financing: Annual loan payments are subtracted from savings each year. The federal tax credit is applied in year 1. After the loan term ends, all electricity savings flow directly to you.
The IRR (Internal Rate of Return) is calculated using Newton's method on the cash flow series. NPV uses a 5% discount rate to express total value in today's dollars.
Frequently Asked Questions
How long does it take for solar panels to pay for themselves?
The average solar payback period in the US is 6–10 years, depending on your system cost, local electricity rates, sun exposure, and available incentives. After the 30% federal tax credit and state incentives, most homeowners see payback in 7–8 years with cash purchases.
What is a good ROI for solar panels?
Solar panels typically deliver a 10–20% internal rate of return (IRR) over 25 years, which outperforms most traditional investments. The exact return depends on your electricity rate, rate increases, system cost, and incentives. Higher electricity rates and faster rate increases improve ROI significantly.
Is it better to pay cash or finance solar panels?
Cash purchases offer the best total return because you avoid interest charges. However, solar loans with low rates (under 5%) can still be financially attractive — you start saving from day one with no upfront cost, and the federal tax credit can be applied to loan payments. The total 25-year savings will be lower than cash but the out-of-pocket investment is zero.
How does solar panel degradation affect long-term savings?
Solar panels degrade at roughly 0.5% per year, meaning a system produces about 88% of its original output after 25 years. This calculator accounts for degradation in the year-by-year projections. The impact is partially offset by rising electricity rates, which increase the dollar value of each kWh produced.
What is NPV and why does it matter for solar investment?
Net Present Value (NPV) shows the total value of your solar investment in today's dollars, accounting for the time value of money. A positive NPV at a 5% discount rate means solar beats a 5% annual return investment. Most residential solar systems have strongly positive NPVs, confirming solar as a sound financial decision.