Solar Panel Payback Calculator
Calculate how many years until solar panels pay for themselves.
Enter system cost, energy production, and electricity rate.
Solar panel payback period is the time it takes for the energy savings generated by a solar system to equal its installation cost. After payback, the system generates essentially free electricity for the remainder of its 25–30 year lifespan.
Simple payback formula: Payback Period (years) = Net Installation Cost ÷ Annual Electricity Savings
Net installation cost: Net Cost = Gross System Cost − Federal Tax Credit − State/Local Incentives − Utility Rebates
Federal Investment Tax Credit (ITC, 2024): 30% of system cost (applies to US homeowners; direct reduction in federal income tax owed)
Annual savings formula: Annual Savings = Annual kWh Production × Electricity Rate ($/kWh)
System production formula: Annual kWh = System Size (kW) × Peak Sun Hours per Day × 365 × System Efficiency Factor
System efficiency factor accounts for inverter losses, shading, temperature, and soiling: typically 0.75–0.85.
What each variable means:
- Peak Sun Hours (PSH) — the equivalent number of hours per day at 1,000 W/m² irradiance:
- Arizona/Nevada: 5.5–6.5 hours/day
- California: 4.5–5.5 hours/day
- Midwest: 4.0–4.5 hours/day
- Northeast US: 3.5–4.5 hours/day
- Pacific Northwest: 3.0–3.5 hours/day
- Electricity rate — US average: $0.14–$0.17/kWh (2024); utilities vary widely from $0.10 (Southeast) to $0.30+ (Hawaii, California)
- Net metering — allows you to sell excess solar energy back to the grid at the retail rate; significantly improves economics in states that offer full retail net metering
Reference: typical US solar installation costs (2024)
- 6 kW system: $15,000–$20,000 gross ($10,500–$14,000 after 30% ITC)
- 8 kW system: $18,000–$25,000 gross ($12,600–$17,500 after ITC)
- 10 kW system: $22,000–$30,000 gross ($15,400–$21,000 after ITC)
Worked example: 8 kW system. Gross cost: $22,000. After 30% federal ITC: $22,000 × 0.70 = $15,400 net cost Location: Texas (5.0 peak sun hours/day). System efficiency: 0.80.
Annual production = 8 kW × 5.0 × 365 × 0.80 = 11,680 kWh/year Electricity rate: $0.13/kWh Annual savings = 11,680 × $0.13 = $1,518/year Payback period = $15,400 ÷ $1,518 = 10.1 years
System lifespan: 25–30 years. Free electricity years = 25 − 10.1 = ~15 years of free electricity Total lifetime savings = 15 × $1,518 = $22,770 after payback (not adjusting for rising electricity rates, which improve the economics further).