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Solar Panel Cost, Size & Payback Calculator

Start with your bill and state. The calculator estimates electricity use, panel count, system size, installed cost, production, simple cash payback and an optional loan payment — while showing every assumption.

1. Your electricity and target

Three inputs create a starting system size. Advanced assumptions stay editable.

No lead form

State2024 EIA residential rate: 31.97¢/kWhAverage monthly electric bill

Estimated use: 563 kWh/monthTarget bill offset 90%25%100%120%

Advanced production assumptions+

Panel rating

System losses

State solar-resource proxy

5.8 hours/day

Recommended starting point

9 panels · 3.6 kW

Estimated installed cost

$16,056

Cost range

$13,648–$18,464

±15% benchmark range

Annual production

6,554 kWh

Modeled, year one

Annual energy value

$2,095

At state average rate

Simple cash payback

7.7 years

Before local incentives

Observed state cost benchmarkEIA 2024 residential rateModeled production2026 federal residential credit: $0

Cash needed

$16,056

Simple payback

7.7 years

25-year net energy value

$33,303

0.5% annual degradation; no rate escalation

Educational estimate: local utility rates, roof orientation, shade, export compensation, installer pricing, financing fees and equipment choices can materially change results. The cost benchmark is historical observed data, not a quote. The production calculation is a state-level screening model; use PVWatts or a site-specific design for address-level analysis.

What the calculator uses

System size

Annual grid use is estimated from your bill and the 2024 EIA residential rate for the selected state. Target solar production equals annual use multiplied by your chosen offset. Required DC size divides that target by peak sun hours, 365 days and the editable system-loss factor.

Installed cost

Covered states use the observed average cost per watt in Tracking the Sun. Other states use the national dataset median as a clearly labeled fallback. The displayed range is ±15% around that benchmark and is not an installer quote.

Savings and payback

First-year savings value solar production at the selected state's average residential rate and cap credited production at estimated annual use. This intentionally avoids assuming favorable export compensation or electricity-price escalation.

Financing

The loan view uses a standard fixed-payment amortization formula. It excludes origination fees, dealer fees, tax effects and future refinancing. Compare its total payments with the cash benchmark and a real lender disclosure.

Sources: Berkeley Lab Tracking the Sun 2024 (observed system costs) · EIA State Electricity Profiles 2024 (residential rates) · state-level solar-resource assumptions benchmarked to PVWatts methodology. New 2026 residential systems receive no federal Residential Clean Energy Credit under current IRS guidance.