Solar Panel Calculator — How Many Panels Do I Need?
☀️ Formula: Daily kWh ÷ Peak Sun Hours = System Size (kW). Panels = System Size (W) ÷ Panel Wattage. Example: 30 kWh/day ÷ 5 sun hours = 6 kW. 6,000W ÷ 500W = 12 panels. Saves $1,620/year at $0.15/kWh. 30% federal tax credit available. Enter your details below — free, no signup.
☀️ Free Solar Panel Calculator — System Size, Panels & Savings
Your Solar System Estimate
System Size:—
—
Number of Panels:—
Roof Area Needed:—
Daily Production:—
Annual Production:—
System Cost (before credit):—
Federal Tax Credit:—
Net Cost (after credit):—
Annual Savings:—
25-Year Savings:—
Payback Period:—
⚠️ Estimates only. Actual numbers vary by location, shading, roof angle and installer.
📋 Key Takeaways — Solar at a Glance
Formula: Daily kWh ÷ Sun Hours = System Size (kW)
Panels = System Size (W) ÷ Panel Wattage
Typical US home: 900 kWh/month = 6-7 kW system = 12-14 panels
Panel size: 400W = ~18 sq ft | 500W = ~22 sq ft
US cost: $2.50-$3.50/watt installed before 30% credit
Payback: 5-7 years in high-rate states, 9-12 years in low-rate
Panels last 25-30 years with 80-85% output at year 25
ℹ️ This free solar panel calculator uses standard NREL formulas and 2026 US pricing. Enter monthly kWh and sun hours to get exact system size, panel count, roof area and 25-year savings. Updated November 2026.
📊 Formulas: System (kW) = Daily kWh ÷ Sun Hours | Panels = System (W) ÷ Panel Wattage | Savings = Monthly kWh × Rate × 12
💡 Pro Tip: Add 10-20% extra panels for winter months and future EV charging. Net metering credits offset low-production days.
📊 System Size by Monthly Usage (Quick Reference)
How many kW do you need? Here's the quick reference (5 peak sun hours):
Monthly kWh
System Size
400W Panels
500W Panels
Roof Area (500W)
500 kWh
3.3 kW
9 panels
7 panels
~154 sq ft
700 kWh
4.7 kW
12 panels
10 panels
~220 sq ft
900 kWh
6.0 kW
15 panels
12 panels
~264 sq ft
1,200 kWh
8.0 kW
20 panels
16 panels
~352 sq ft
1,500 kWh
10.0 kW
25 panels
20 panels
~440 sq ft
📊 Peak Sun Hours by US Region
Region
Peak Sun Hours
Example States
Southwest
6.0-7.5
AZ, NM, NV, Southern CA
Southeast
4.5-5.5
FL, GA, SC, NC
Texas / Plains
5.0-6.0
TX, OK, KS
Midwest
4.0-4.5
IL, OH, MI, IN
Northeast
3.5-4.5
NY, PA, MA, NJ
Pacific Northwest
3.0-4.0
WA, OR, Northern CA
☀️ 2,000 sq ft Home — Austin, TX
Usage: 1,100 kWh/month | 5.5 sun hours | 500W panels
Use the calculator above for your exact usage and sun hours.
What is a Solar Panel Calculator and How Does It Work?
A solar panel calculator determines how many panels you need based on your electricity usage and location. Our solar panel calculator uses standard NREL formulas to convert monthly kWh into system size (kW), then divides by panel wattage to get the number of panels.
How does the calculator work? Enter monthly kWh, peak sun hours, panel wattage, electricity rate and cost per watt. The calculator instantly shows system size, panel count, roof area, production, cost, savings and payback period.
Annual production: multiply daily by 365, then reduce by 15-20% for real-world losses (inverter, wiring, shading).
How Much Roof Area Do You Need?
Residential panels are about 18 sq ft (400W) or 22 sq ft (500W). Add 15% for spacing and setbacks.
6 kW system (12 × 500W): 264 sq ft + 15% = ~304 sq ft
8 kW system (16 × 500W): 352 sq ft + 15% = ~405 sq ft
10 kW system (20 × 500W): 440 sq ft + 15% = ~506 sq ft
How Much Does Solar Cost in the USA?
US (2026): $2.50-$3.50/watt installed before the 30% federal tax credit. A 6 kW system costs $15,000-$21,000, or $10,500-$14,700 after credit.
State incentives (CA, NY, MA, NJ) can reduce cost further by $2,000-$5,000. Total cost after all incentives: $8,500-$12,700 for a 6 kW system.
How Long Is the Payback Period?
Formula: Payback = Net System Cost ÷ Annual Savings.
Example: $10,500 net cost ÷ $1,620 annual savings = 6.5 years.
In high-electricity states (CA, NY, MA): 5-7 years. In low-rate states: 9-12 years. After payback, all savings are pure profit for 18-20 more years.
Do Solar Panels Increase Home Value?
Yes. Studies show solar adds 3-4% to US home resale value. A $400,000 home with solar could sell for $12,000-16,000 more. Some buyers pay a premium for lower electricity bills.
30% Federal Solar Tax Credit (2026)
The Residential Clean Energy Credit gives 30% of system cost back as a federal tax credit. Available through 2032. No cap. Applies to panels, inverters, batteries, labor and permits.
Example: $15,000 system = $4,500 tax credit. You must owe at least $4,500 in federal tax to use the full credit in one year. Unused credit rolls forward.
Why Use Our Solar Panel Calculator?
Our free solar panel calculator is built for accuracy and speed. It runs entirely in your browser — no sign-up, no data stored. The calculator uses NREL sun hour data and 2026 US pricing. Whether you're comparing quotes, planning a system, or just curious about savings, our tool delivers professional-grade results in seconds.
❓ Frequently Asked Questions
How many solar panels do I need?
Formula: Daily usage (kWh) ÷ Peak sun hours = System size (kW). Then System size (W) ÷ Panel wattage = Number of panels. Example: 30 kWh/day ÷ 5 sun hours = 6 kW system. 6,000W ÷ 500W panels = 12 panels. Use the calculator above for exact USA numbers.
How many kW solar system do I need for a US home?
Average US home uses 900 kWh/month (30 kWh/day). At 5 peak sun hours: 30 ÷ 5 = 6 kW system. In Southwest (6.5 sun hours): 4.6 kW. In Northeast (4 sun hours): 7.5 kW. System size depends on location.
How many solar panels for a 2,000 sq ft US home?
A 2,000 sq ft US home uses about 900-1,000 kWh/month. That needs a 6-7 kW system = 12-14 panels of 500W each. Roof area: about 400-500 sq ft. Exact number depends on state sun hours and panel wattage.
How many kWh does a 400W solar panel produce in the USA?
A 400W panel produces about 1.6-2.0 kWh per day in US sun (4-5 peak sun hours). That is 50-60 kWh per month, or 600-720 kWh per year. Southwest produces more, Northeast less.
How much roof area do I need for solar panels?
A 400W panel is about 18 sq ft. A 500W panel is about 22 sq ft. For a 6 kW system (12 × 500W panels), you need about 264 sq ft of roof area. Add 15% for spacing and setbacks.
How much does a solar system cost in the USA?
US solar costs $2.50-$3.50 per watt installed before incentives. A 6 kW system costs $15,000-$21,000. After the 30% federal tax credit, net cost is $10,500-$14,700. State incentives can reduce it further.
How much can I save with solar panels in the USA?
Savings = Monthly kWh × Electricity rate. For 900 kWh at $0.15/kWh = $135/month, or $1,620/year. Over 25 years: $40,500. After subtracting system cost ($10,500-$14,700 net), net savings are $25,800-$30,000.
What is the payback period for solar panels in the USA?
Payback = Net cost ÷ Annual savings. For a $14,700 system saving $1,620/year: payback is about 9 years. In high-electricity states (CA, NY, MA), payback can be 5-7 years. In low-rate states, 12-15 years.
Residential panels are 400-450W in 2026, with 500-550W becoming common. Higher wattage panels mean fewer panels and less roof space. 400W panels are about 18 sq ft; 500W panels are about 22 sq ft.
Does the 30% federal solar tax credit still exist in 2026?
Yes. The Residential Clean Energy Credit (30%) is available through 2032 under the Inflation Reduction Act. There is no cap on the credit amount. It applies to solar panels, batteries and installation.
Do solar panels increase home value in the USA?
Yes. Studies show solar adds 3-4% to US home resale value. A $400,000 home with solar could sell for $12,000-16,000 more. Some buyers pay a premium for lower electricity bills.
💡 Expert Tips for Going Solar in the USA
Tip #1: Reduce electricity usage first (LED, efficient appliances). Every kWh reduced means a smaller, cheaper system.
Tip #2: Get 3-5 US installer quotes. Prices vary by $0.50-$1.00/watt between installers for the same system.
Tip #3: Check your roof condition before installing. A 15-20 year old roof may need replacement first.
Tip #4: Understand your net metering policy. Some US utilities pay 1:1 for exports, others pay wholesale.
Tip #5: Consider a battery if you have frequent outages or time-of-use rates. Batteries add $8,000-$15,000.
Tip #6: Install before the 30% federal credit expires (currently through 2032).
☀️ Still Asking "How Many Solar Panels Do I Need?"
Enter monthly kWh. Get exact system size and savings in 30 seconds. Free, no signup.
🛡️ CDCalculators solar panel calculator — data sources: NREL sun hour data, 2026 US solar pricing, EIA electricity rates. Last updated November 12, 2026. Disclaimer: Estimates only. Get 3+ installer quotes before purchase.