Solar System Size Calculator

Solar System Size Calculator

Calculate the perfect solar panel system size for your home. Get accurate estimates for panels, production, and savings.

Enter Your Details

Check your electricity bill for this value

Typical range: 4-5 hours (peak sun hours)

Accounts for inverter loss, dust, temperature

Your Results

Required System Size

0.00 kW

Number of Solar Panels

0 panels

Est. Daily Production

0.00 kWh

Est. Annual Production

0 kWh

Why Use Our Calculator

Discover what makes our solar calculator the trusted choice for homeowners and professionals alike.

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Instant Results

Get accurate solar system sizing calculations in seconds, saving you hours of manual computation.

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Precision Accuracy

Our algorithm accounts for system losses, ensuring you get realistic production estimates.

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Cost Effective

Avoid over-sizing or under-sizing your system. Get the perfect fit for your energy needs.

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Comprehensive Data

View daily, monthly, and annual production estimates all in one convenient dashboard.

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Customizable Inputs

Adjust panel wattage, sunlight hours, and loss factors to match your specific situation.

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Works Everywhere

Whether you’re in sunny Arizona or cloudy Seattle, our calculator adapts to your location.

How to Use Our Calculator

Follow these simple steps to determine your ideal solar panel system size.

01
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Find Your Usage

Check your electricity bill for your monthly kWh consumption. This is usually prominently displayed.

02
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Enter Sunlight Hours

Input your area’s peak sun hours. Most regions range from 4-5 hours. Check online for your location.

03
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Select Panel Wattage

Choose your preferred panel wattage. Higher wattage means fewer panels needed for the same output.

04
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Adjust System Loss

Keep the default 20% or adjust based on your system’s efficiency and local conditions.

05
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Click Calculate

Press the calculate button and watch as your personalized solar system specifications appear instantly.

06
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Review Results

Analyze your required system size, panel count, and production estimates to make informed decisions.

Frequently Asked Questions

Get answers to the most common questions about solar system sizing.

How do I find my monthly electricity usage?
Your monthly electricity usage is listed on your utility bill, typically shown in kilowatt-hours (kWh). Look for terms like “Total Usage,” “Energy Used,” or “kWh Consumed.” You can also check your online utility account or contact your provider. For the most accurate sizing, use an average of your past 12 months of usage to account for seasonal variations.
What are peak sunlight hours and how do I find mine?
Peak sunlight hours refer to the hours when the sun’s intensity averages 1,000 watts per square meter. This isn’t the same as daylight hours—it’s a measure of usable solar energy. In the US, this typically ranges from 3-6 hours depending on location. Southern states average 5-6 hours, while northern states average 3-4 hours. You can find your specific value using online solar irradiance maps or the NREL PVWatts calculator.
Why is there a system loss factor?
The system loss factor accounts for real-world efficiency losses that prevent solar panels from achieving their rated output. These losses include: inverter conversion (2-4%), temperature effects (5-15%), dust and soiling (2-5%), wiring losses (1-2%), and shading (varies). A 20% total loss factor is standard for most installations, but you may adjust this based on your specific conditions.
Should I choose 350W, 400W, or 450W panels?
Higher wattage panels produce more power per panel, meaning you need fewer panels for the same system size. 400W panels are currently the most popular choice, offering a good balance of efficiency and cost. Choose 450W panels if you have limited roof space. 350W panels may be suitable if you’re on a tighter budget or have ample roof space. All options can achieve the same total system output with different panel counts.
How accurate is this calculator?
Our calculator provides reliable estimates based on industry-standard formulas used by solar professionals. However, actual production can vary by 5-10% based on factors like roof orientation, tilt angle, local shading, and weather patterns. For a precise quote and system design, we recommend consulting with a certified solar installer who can perform an on-site assessment and use satellite imagery for detailed analysis.

What Users Say

Join thousands of homeowners who’ve used our calculator to plan their solar journey.

★★★★★

“This calculator helped me understand exactly what I needed before talking to installers. I wasn’t oversold on a bigger system than necessary. The estimates were spot-on with what my system actually produces!”

MJ

Michael Johnson

Homeowner, Phoenix AZ

★★★★★

“As someone new to solar, I was overwhelmed by all the technical jargon. This calculator made everything simple and easy to understand. I finally knew what questions to ask the installers.”

SR

Sarah Rodriguez

Homeowner, Austin TX

★★★★★

“I use this tool with all my clients to give them quick estimates. It’s professional, accurate, and saves me time during initial consultations. Highly recommend for both homeowners and installers!”

DK

David Kim

Solar Installer, San Diego CA

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