TrimWatt
Data sourced from the U.S. Dept. of Energy, Energy Star, and the EIA.

Solar Savings Calculator

Estimate your system size, installed cost, and payback period from your bill and local sun hours.

$180
4.5
17¢
90%

Sun hours vary by region — check PVWatts for your address.

ESTIMATED SYSTEM SIZE
≈ 7.0 kW
Possible yearly savings
≈ $1,940
about 10 yr payback · $20,190 net cost
Rounded estimate — free, no sign-up, nothing collected.

Estimate, not a guarantee.Rounded for guidance. Your figures depend on your home, local rates, and usage.

How we calculate this

Formula: System size = (annual kWh × offset target) ÷ (daily sun hours × 365). Installed cost = size × $2.90/W (no federal credit applies in 2026). Payback = installed cost ÷ annual savings.

Assumptions:

  • An installed cost near $2.90/W before incentives — a national ballpark, not a quote.
  • No federal credit is applied: the 25D residential credit ended for expenditures after 31 December 2025. State and utility incentives are not included either.
  • Exported energy is credited at or near retail rate (net metering), which is not true everywhere.

Limits: It ignores shading, roof orientation, roof condition, and local permitting costs. Use it to sanity-check an installer's quote, never to replace a site assessment.

Sources: National Renewable Energy Laboratory · U.S. Energy Information Administration

Related guides

Frequently asked questions

How is solar payback calculated?

Payback is the installed system cost divided by your estimated annual savings. No federal credit is applied: the Residential Clean Energy Credit (25D) terminated for expenditures after 31 December 2025. State, local, and utility incentives can still shorten it.

Is this a substitute for an installer quote?

No — it's a sanity check. Use it to know roughly what to expect before you compare real quotes.

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