Solar Panel Calculator
Estimate system size, cost after incentives, annual savings, and payback from your electricity bill
Related calculators
All energy- Home Battery Backup CalculatorBackup runtime during an outage and batteries needed for a target
- Electricity Cost CalculatorWhat any appliance costs to run per day, month, and year
- EV Savings CalculatorCompare electric vs gas fuel cost per year, per mile, and lifetime
- Carbon Footprint CalculatorAnnual household CO2 from energy and travel, broken down by source
- HVAC SEER Savings CalculatorCooling energy and cost saved by upgrading to a higher SEER
- LED Savings CalculatorEnergy, money, and CO2 saved by switching bulbs to LED
Quick summary
Enter your monthly electricity usage, rate, and local peak sun hours to size a solar system, count the panels, and estimate its cost after incentives, yearly savings, payback period, and 25-year net savings. A 900-kWh/month home at $0.16/kWh with 4.5 sun hours needs roughly a 8.4-kW system (21 panels), costs about $17,600 after a 30% credit, saves ~$1,700/year, and pays back in around 10 years. It assumes ~80% system efficiency and savings at your retail rate up to your usage; real results depend on local sun, net-metering rules, and roof orientation.
Reviewed by Simple Calculators TeamLast reviewed
How to use this calculator
- Enter the inputs requested by the calculator.
- Choose the units or options that match your situation and review the assumptions.
- Run or update the calculation to see the result.
- Review the result, breakdown, and formulas shown on the page.
- Check the inputs, units, dates, and limitations before saving or sharing the result.
Frequently asked questions
How many solar panels do I need?
It depends on your electricity use, local sun hours, and panel wattage. Divide your target annual production by (sun hours × 365 × ~0.8 efficiency) to get system size in kW, then divide by panel wattage. This calculator does it from your monthly usage — a typical home lands around 15–25 panels.
How long until solar pays for itself?
Payback is the net system cost (after incentives) divided by annual savings. In sunny areas with high electricity rates, 6–10 years is common; in cloudier regions with cheap power it can stretch to 12+ years. After payback, the remaining ~15 years of panel life is largely free electricity.
What is the 30% solar tax credit?
The federal Residential Clean Energy Credit covers 30% of the cost of a home solar system through 2032, with no dollar cap, applied against your federal tax liability. Many states and utilities add their own rebates. Enter your combined incentive percentage to see the net cost. Confirm current rules, as they change.
Does this account for net metering?
It approximates it: savings are credited at your retail rate for production up to your annual usage, which mirrors full retail net metering. Where utilities pay less than retail for exported power (net billing), or cap credits, your real savings may be lower. Check your utility's specific policy.
Key terms
- Peak Sun Hours
- Daily hours of full-strength sun equivalent for your location; drives production.
- kW (System Size)
- The array's rated power; sized to your usage and sun hours.
- Payback Period
- Years for savings to recoup the net cost of the system.
- Net Metering
- Utility crediting you for solar power you export to the grid.
Methodology, sources & limitations
This page shows the formula, assumptions, and limitations used for this estimate. Rates, thresholds, and other time-sensitive inputs can change, so verify them against the relevant official source before relying on a result.
For our review approach and the primary sources we consult, see the methodology and source policy. If you spot an outdated figure or formula, please contact us with a correction.