Solar Panel ROI Calculator
Estimate solar panel system payback and lifetime savings. Calculate annual production, net cost after incentives, and 25-year return on investment.
⚠️ Results are for informational purposes only. Verify against applicable codes and manufacturer specifications before use. Always consult a licensed electrician/HVAC contractor and your local AHJ (Authority Having Jurisdiction) before performing work.
Guides are drafted with AI assistance and reviewed by our editors.
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How to Calculate Solar Panel ROI
Understanding Solar Panel Economics
Solar panels are a long-term investment. The key question isn't whether solar saves money — it does — but how quickly it pays for itself. The answer depends on system size, local sun hours, electricity rates, available incentives, and system cost.
The IRS Section 25C Residential Clean Energy Credit provides a 30% federal tax credit (through 2032) for solar installations. Many states offer additional incentives, SREC programs, or net metering policies that further improve returns.
The Solar ROI Formula
Annual Production: kWh = kW × sun_hours × 365 × 0.80
(0.80 derate factor covers inverter losses, soiling, wiring, temperature, and shading)
Year 1 Savings: S₁ = Production × Rate ($/kWh)
Net Cost: Net = Installed_Cost × (1 - Incentive%)
Simple Payback: Years = Net_Cost / S₁
25-Year Cumulative: Σ S₁ × (1 + rate_increase)^year for year 0..24
25-Year ROI: (Cumulative_Savings - Net_Cost) / Net_Cost × 100%
The 0.80 system efficiency derate is consistent with NREL PVWatts methodology. The 25-year analysis period matches typical panel warranty periods (25 years performance guarantee).
Worked Example
Scenario: 6 kW system, 5 peak sun hours/day, $18,000 installed, $0.15/kWh rate, 3% annual increase, 30% federal tax credit.
- Annual Production: 6 × 5 × 365 × 0.8 = 8,760 kWh/year
- Year 1 Savings: 8,760 × $0.15 = $1,314/year
- Net Cost: $18,000 × (1 - 0.30) = $12,600
- Simple Payback: $12,600 / $1,314 = 9.6 years
- 25-Year Savings: With 3% rate increase, cumulative ≈ $47,000+ gross savings → net ~$34,400
Practical Tips
- Net metering matters: Full retail net metering effectively credits solar production at your full retail rate. If your utility only offers avoided cost (wholesale rate) for excess, your actual savings will be lower than this calculator estimates.
- Panel degradation: Panels typically lose 0.5% output per year. Over 25 years, production drops to about 88% of year 1. This calculator uses flat production for simplicity — real-world savings will be slightly lower in later years.
- South-facing is optimal: In the Northern Hemisphere, panels facing true south at a tilt angle equal to your latitude produce the most energy. East/west orientations produce about 80–85% of optimal output.
- Get multiple quotes: Solar pricing varies significantly. The national average is $2.50–3.50/W installed, but competitive bids can be lower. Don't pay more than $3.50/W without premium equipment or complex installations.
Code References
NREL PVWatts, IRS Section 25C