Solar Panel Payback Calculator

Enter your monthly electric bill and state. We'll size a rooftop system for your home, apply 2026 incentives, and tell you when it pays off — and how much you'll save over 25 years.

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Tip: your installer quote should be within ~10% of $2.85/watt. Anything above $3.50 is overpriced for most markets.

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How this calculator works

We size your system to cover your actual annual electricity consumption. The steps:

  1. Usage estimate: Monthly bill ÷ state-average residential rate = annual kWh needed.
  2. System sizing: Annual kWh ÷ (peak sun-hours × 365 × 0.80 performance ratio) = required kW.
  3. Cost: kW × 1,000 × $/W installed, minus any state/utility rebate you enter.
  4. Savings: Year-by-year production, derated 0.5%/yr for panel degradation, times your utility rate, inflated 3%/yr.
  5. Payback: The year in which cumulative savings first exceed net cost.

What the 2026 tax-credit landscape looks like

The federal residential solar tax credit (Section 25D, formerly known as the ITC) fully stepped down at the end of 2025 for most new residential installations. However:

  • State-level rebates remain strong in California, New York, Massachusetts, Colorado, Illinois, and New Jersey.
  • Net-metering policies vary wildly: states like Arizona and California have moved to "net billing" (export credits lower than retail), which extends payback by 1-3 years.
  • Performance-based incentives (SRECs) in PJM states can add $400-1,200/yr of revenue.

Our calculator assumes retail-equivalent net metering. If your utility uses net billing, increase payback estimates by 15-25%.

Is solar worth it without the federal tax credit?

In many states — yes, but payback periods have stretched from 6-8 years to 9-12 years for most markets. In very sunny, high-utility-rate states (CA, AZ, NM, HI), it's still a strong investment. In low-sun, low-rate states (WV, KY, WA-east), it's harder to justify on pure ROI alone.

Common mistakes that inflate installer quotes

  • Overly large systems. You gain almost nothing from production above your annual use, if your utility uses net billing.
  • Unnecessary battery bundling. A battery adds $10-18k; it's a great backup product but usually extends total payback by 3-5 years.
  • High-premium panel brands. The difference between a Tier-1 panel and a "premium" panel is often ~1-2% efficiency, but 30-50% more cost.
WattWise estimates are for educational purposes only and are based on public utility rate data, NREL sun-hour averages, and industry installed-cost benchmarks. Actual quotes, production, and savings will vary based on roof condition, shading, local permitting, and utility policy changes. This is not a binding quote or financial advice.