728 × 90 Leaderboard

320 × 100 Mobile Banner

Solar Panel Calculator

Estimate solar panel system size and savings for your home.

Last updated: June 13, 2026

Calculator

Monthly Electric Bill

Electricity Rate

cents/kWh

Peak Sun Hours/Day

Results

System Size8.9 kW

Panels Needed23

400W panels

Est. System Cost$26,786

Before incentives (~$3/watt)

Payback Period14.9 years

Saving ~$1,800/year

How to Use This Calculator

1Enter your monthly electricity bill in dollars.
2Enter your electricity rate per kWh.
3Enter average sun hours per day for your area.
4View recommended system size, panel count, and payback period.

Formula Explanation

System size is determined by your electricity usage and available sunlight. Annual savings are based on energy offset by solar production.

Monthly kWh = Bill ÷ Rate System kW = (Monthly kWh × 12) ÷ (Sun Hours × 365 × 0.80) Panels = System kW ÷ 0.4

Variables:

BillMonthly electricity bill in dollars

RateCost per kWh

Sun HoursAverage peak sun hours per day

0.80System efficiency factor (losses)

Worked Examples

$150/month bill, $0.12/kWh, 5 sun hours/day

1. Monthly usage = $150 ÷ $0.12 = 1,250 kWh
2. Annual usage = 15,000 kWh
3. System size = 15,000 ÷ (5×365×0.80) = 10.3 kW
4. Panels needed = 10.3 ÷ 0.4 = 26 panels
5. Cost estimate = 10.3 × $3,000 = $30,900 (before incentives)
6. After 30% tax credit = $21,630

Result: 10.3 kW system, 26 panels, ~$21,630 after tax credit

Why Use This Calculator

Estimate your ideal solar system size.
Calculate payback period and ROI.
See impact of the 30% federal tax credit.
Compare solar savings vs utility costs.

336 × 280 Large Rectangle

300 × 250 Medium Rectangle

Tips & Best Practices

The federal solar Investment Tax Credit (ITC) is 30% through 2032.
Average solar payback period is 6-10 years depending on location and rates.
Solar panels last 25-30 years and most come with 25-year warranties.
Peak sun hours vary from 3-4 (Pacific Northwest) to 6-7 (Southwest).

Common Mistakes to Avoid

❌ Confusing sun hours with daylight hours.

✅ Peak sun hours (PSH) measure solar intensity, not just daylight. Seattle has 3-4 PSH while Phoenix has 6-7 PSH, even though both have similar daylight hours in summer.

❌ Not factoring in the federal tax credit.

✅ The 30% federal ITC significantly reduces net cost. A $30K system costs $21K after the credit. Some states offer additional incentives.

Frequently Asked Questions

How many solar panels do I need?

The average US home (900 kWh/month) needs a 6-8 kW system, which is about 15-20 panels. This varies based on your usage and local sun hours.

Is solar worth it?

In most US states, yes. With the 30% tax credit, 6-10 year payback, and 25+ year panel life, solar typically provides 200-400% ROI over its lifetime. Electricity rates also tend to rise 2-3% annually.

336 × 280 Large Rectangle

300 × 250 Medium Rectangle

Embed This Calculator

Add the Solar Panel Calculator to your website for free. Copy the code below and paste it into your HTML.

Width

Height

<iframe src="https://redicalc.com/embed/home/solar-panel-calculator" width="100%" height="600" style="border:none;border-radius:12px;box-shadow:0 1px 3px rgba(0,0,0,0.1);" title="Solar Panel Calculator — RediCalc.com" loading="lazy" allowtransparency="true"></iframe>

Preview embedFree to use · Attribution link included

Disclaimer: This calculator is provided for informational and educational purposes only. Results are estimates and should not be used as a substitute for professional advice. RediCalc.com makes no guarantees regarding the accuracy, completeness, or suitability of any calculations. Always consult a qualified professional before making financial, health, construction, or other important decisions.

160 × 600Skyscraper