SOLAR CALCULATOR
Solar Panel Savings Calculator
Use your bill, local rate, sun hours, and target coverage to estimate a preliminary home solar system.
✓ Free✓ Instant results✓ No sign-up
ADVERTISEMENT
LIVE CALCULATOR
Updates instantlyEstimate system size, annual savings, and simple payback
$
$/kWh
hours/day
%
$/watt
Formula: System size = target annual kWh ÷ (peak sun hours × 365 × performance factor)
ADVERTISEMENT
How this estimate works
This is an early planning estimate—not a site survey or installer quote.
- Use your equipment data. Check a label, specification sheet, controller, or energy meter.
- Enter your utility rate. A recent bill is more useful than a national average.
- Test different schedules. Change one input at a time to compare scenarios.
Ways to reduce or refine the cost
1
Use 12 months of bills to capture seasonal consumption.
2
Request a roof-specific shade and production assessment.
3
Compare cash price, financing, warranties, and utility export compensation.
Transparent methodology
Results use the values you enter and standard energy formulas. They are planning estimates, not bills or guarantees.
Frequently asked questions
What is a peak sun hour?+
It represents one hour of solar irradiance at 1,000 watts per square meter.
Why use an 80% performance factor?+
It allows for temperature, inverter, wiring, soiling, orientation, and system losses.
Are tax credits included?+
No. Gross cost and payback do not include incentives or financing.
How to verify this estimate
Best input
Model production, self-consumption, exports, and tariff rules separately.
Reality check
Compare the preliminary result with a site-specific proposal using documented assumptions.
Important limitation
Roof geometry, shading, degradation, financing, incentives, and net-metering rules can dominate payback.
Primary reference: NREL PVWatts. Reviewed September 2026.