Solar design software has become the backbone of the US solar industry. Before software, installers spent days producing hand-drawn layouts, manual shading calculations, and spreadsheet-based yield estimates. Today, a professional can model an entire residential system in under an hour — with bankable production estimates, automated permit drawings, and integrated financing tools. Here’s what’s available in 2026 and what each tool does best.
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Why Solar Design Software Matters
Solar design software does several things simultaneously: it models a roof’s geometry and orientation from aerial or satellite imagery, calculates shading from trees, chimneys, and neighboring buildings across every hour of the year, sizes the array and inverter to maximize production, and generates the proposal, permit drawings, and interconnection paperwork the installer needs to close and complete the job.
For homeowners, this matters because the quality of your system design directly affects how much electricity it produces. A poorly designed system with unaddressed shading or an undersized inverter can underperform its estimate by 10–20% or more. A well-designed system matched accurately to your load profile will hit its projected numbers within 3–5%.
Top Solar Design Software Tools in 2026
Aurora Solar
Aurora Solar is the most widely used commercial solar design platform in the US, with over 10,000 solar companies on the platform. It uses LiDAR data and AI to model roofs in 3D without a site visit, runs hour-by-hour shading simulations, and generates full sales proposals and permit drawings. Production estimates typically land within 3% of actual first-year output.
Aurora’s AI-powered “AutoDesign” feature can produce a code-compliant design in seconds from a satellite view. The platform integrates with CRMs, financing tools, and permit submission services. Pricing starts around $349/month for small teams.
Helioscope (Folsom Labs / Enphase)
Helioscope is widely used by engineers and larger commercial installers for its detailed electrical simulation capabilities. Acquired by Enphase Energy in 2021, it integrates tightly with Enphase microinverter and IQ systems. Helioscope’s strength is multi-configuration analysis — it lets you compare multiple designs side by side and assess wiring layouts in depth. Better for commercial and complex projects than for residential sales.
PVWatts (NREL)
PVWatts is a free, browser-based tool from the National Renewable Energy Laboratory. You enter system size, location, tilt, and azimuth, and it returns estimated annual kWh production based on historical weather data. It doesn’t do shading or electrical design, but it’s the industry standard for quick sanity checks and is accepted by utilities for interconnection applications. pvwatts.nrel.gov
OpenSolar
OpenSolar is a free-to-use platform for solar installers that covers the full sales and design workflow: 3D roof modeling, automated shading, system sizing, proposal generation, and e-signature. The business model is free for installers, with revenue from financing and hardware partnerships. Popular among smaller installers who can’t afford Aurora’s subscription costs.
SAM (System Advisor Model)
NREL’s System Advisor Model is free, downloadable software designed for detailed technical and financial analysis of renewable energy systems. It can model residential and commercial PV, concentrating solar, wind, and more. SAM is commonly used by engineers, researchers, and utilities for bankable energy yield assessments. Steeper learning curve than commercial tools, but extremely detailed. sam.nrel.gov
SolarEdge Designer
SolarEdge’s proprietary design tool is specifically built for systems using SolarEdge inverters and power optimizers. It includes string sizing, optimizer placement, layout generation, and performance simulation. Free to use but limited to SolarEdge equipment — useful for installers who primarily work with SolarEdge products.
PVsyst
PVsyst is Swiss-developed software widely regarded as the industry standard for utility-scale project modeling. It’s expensive (around $1,800/year per license) and has a steep learning curve, but produces the detailed, bankable yield assessments required for project finance and PPA negotiations. Rarely used for residential installations.
Key Features to Look For
- 3D shading analysis: Hour-by-hour simulation of shade from trees, chimneys, and neighboring structures.
- LiDAR or AI roof modeling: Accurate 3D roof geometry without a site visit reduces design time and errors.
- Electrical design: String sizing, wire runs, disconnect placement, and NEC code compliance.
- Financial modeling: Payback period, NPV, IRR, loan comparisons.
- Permit packages: Automated generation of permit-ready drawings reduces timelines significantly.
Free vs. Paid Solar Design Tools
Free tools (PVWatts, OpenSolar, SolarEdge Designer) cover basic needs and are appropriate for homeowners doing DIY research. If you’re trying to independently verify the production estimate an installer gave you, PVWatts is the fastest way to do that — enter your address, system size, and orientation, and compare the annual kWh estimate to what you were quoted.
Paid commercial platforms like Aurora Solar and PVsyst are built for professional use. As a homeowner, it’s reasonable to ask your installer which software they design with and request a copy of the shade report.
How Homeowners Can Use Solar Design Software
- Ask if the installer ran a shading analysis, and request the report.
- Ask what production figure (annual kWh) they’re designing to, and how they derived it.
- Use PVWatts to do an independent estimate — if their numbers are more than 15% above PVWatts, ask why.
- Ask how the design accounts for future shading as trees grow.
Want a quote from installers who use professional design software? Call (855) 427-0058 for a free solar assessment from vetted local installers.
Frequently Asked Questions
What software do solar installers use?
The most widely used software among US residential solar installers is Aurora Solar, followed by OpenSolar and Helioscope. Many smaller installers use PVWatts for production estimates and combine it with CAD software for permit drawings.
Is there free solar design software?
Yes. PVWatts (NREL) is free and browser-based. OpenSolar is free for installers. SAM is free for download and handles advanced analysis. SolarEdge Designer is free for systems using SolarEdge components.
Can I design my own solar panel system?
With tools like PVWatts and OpenSolar, a technically confident homeowner can model a system and estimate production. However, permit-ready drawings typically require licensed electrical engineering stamps in most jurisdictions.
How accurate are solar design software predictions?
The best commercial platforms typically achieve production estimates within 3–5% of actual first-year output when the shading model is accurate. PVWatts estimates can vary more widely — typically ±10–15% — because they use simplified shading assumptions.
Summing Up
Solar design software is what separates a well-engineered installation from a guesswork-based one. Aurora Solar and OpenSolar dominate the residential market; PVWatts is the go-to free tool for quick estimates; PVsyst and SAM handle complex commercial and utility projects. Ask your installer to share the shade analysis and use PVWatts to double-check the numbers.
Ready to get a professionally designed solar system? Call (855) 427-0058 to connect with experienced local installers who stand behind their production estimates.
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