Exploring Solar Design Software

Solar design software has transformed how installers, engineers, and contractors bring a solar project from site visit to energization. What once required days of hand calculations, manual shading analysis, and paper permit drawings now takes under an hour with the right platform. Whether you’re a professional installer evaluating tools or a homeowner curious what goes into your system design, here’s a complete look at the leading solar design software in 2026 — what each does, who it’s for, and what it costs.

What Solar Design Software Does

Modern solar design software handles several overlapping functions that installers used to manage with separate tools:

Roof modeling: Using LiDAR data, satellite imagery, and AI-powered plane detection, platforms automatically map roof geometry — pitch, azimuth, ridgelines, obstructions — without manual measurement. High-end tools can model a residential roof in seconds from satellite imagery alone.

Shading analysis: Software calculates irradiance at every point on the roof using sun-path data and obstruction geometry. Shade from trees, chimneys, neighboring buildings, and HVAC units is modeled hour by hour across the full year. This directly determines panel placement, production estimates, and inverter selection.

Production estimation: Energy yield models combine irradiance data, panel efficiency curves, temperature coefficients, soiling estimates, and system losses to produce bankable kWh/year estimates. Most platforms use NREL’s TMY (Typical Meteorological Year) weather data as the foundation.

Equipment configuration: Drag-and-drop panel placement, string sizing, inverter selection, and battery integration all happen within the design tool. Electrical one-line diagrams and wiring schematics are auto-generated.

Permit drawings: Platforms like Aurora and OpenSolar auto-generate AHJ-compliant permit packages — site plans, electrical diagrams, structural loading calculations — reducing permitting prep from hours to minutes.

Financial modeling: Proposal tools calculate system cost, monthly savings, payback period, IRR, and financing options (loans, leases, PPAs). Some platforms integrate directly with Mosaic, GoodLeap, or Sungage for embedded loan applications.

Professional Solar Design Software

Aurora Solar

Aurora Solar is the dominant platform for US residential and commercial solar installers. After acquiring Folsom Labs (makers of Helioscope) in 2022, Aurora consolidated two of the industry’s leading tools under one company, though both products continue to operate independently.

Aurora’s core differentiator is its AI-powered roof modeling engine: upload an address and the platform auto-generates a 3D roof model with detected planes, obstructions, and tree canopy — often without any manual editing. The financial proposal tool integrates with major solar lenders and generates customer-facing proposals in branded formats.

Best for: Residential and light commercial installers, sales teams that need integrated proposal tools, companies using automated permitting via SolarAPP+.

Pricing: Aurora’s pricing isn’t publicly listed and varies by company size and feature tier, but published reports place it in the $1,500–$3,500/year range per user for mid-market installers. Enterprise contracts for larger companies are negotiated separately.

Limitations: Higher cost than competitors, and some engineers prefer Helioscope for complex commercial projects because of its more detailed loss modeling.

Helioscope (Folsom Labs / Aurora)

Helioscope remains the tool of choice for engineers and energy consultants doing detailed commercial and utility-scale feasibility modeling. Unlike Aurora’s sales-focused workflow, Helioscope is engineering-first: its loss tree modeling breaks down system performance by wiring losses, mismatch losses, soiling, and degradation in granular detail. Banks, EPCs, and project developers use Helioscope’s outputs for financial due diligence.

Best for: Commercial and utility-scale projects, engineering firms, independent energy consultants, anyone who needs bankable production reports for project financing.

Pricing: ~$1,500–$2,000/year per user. Still sold separately from Aurora despite the parent company acquisition.

OpenSolar

OpenSolar launched in 2016 with a disruptive model: free for solar installers, with revenue generated from its integrated marketplace for panels, inverters, and batteries. It’s now used by installers in over 100 countries and is the most widely deployed free professional platform globally.

Feature-wise, OpenSolar covers the full workflow — 3D roof modeling, shading analysis, production estimates, permit documents, proposals, and financing. Its global weather data coverage is broader than US-centric platforms, making it popular for international projects.

Best for: Small to mid-size installers, startups, international projects, companies that want a professional tool without subscription cost.

Pricing: Free (core features). Premium add-ons (advanced reports, custom branding, API access) available at additional cost.

Limitations: Less AI-powered roof modeling automation than Aurora; shading accuracy slightly less precise on complex rooflines. The freemium model means OpenSolar upsells equipment purchases through its marketplace.

Solargraf (Sunbase Data)

Solargraf is a cloud-based solar CRM and design platform that combines lead management, proposal creation, and system design in one product. It’s positioned for residential sales teams that want the full pipeline from lead to signed contract within a single tool. Solargraf was acquired by Sunbase Data in 2022, which added CRM and project management capabilities.

Best for: Residential installers who want a combined CRM + design + proposal platform. Strong for teams where sales reps (not engineers) create proposals.

Pricing: Varies by tier; starts around $99/month for small teams.

Free and Government Tools

PVWatts (NREL)

PVWatts is NREL’s free online solar production calculator — the most widely cited tool in the US solar industry for independent production verification. It uses TMY3 weather data from hundreds of US locations, accepts system parameters (DC system size, array type, tilt, azimuth, system losses), and outputs monthly and annual AC energy production.

PVWatts doesn’t do roof modeling or permit drawings. It’s a production estimation engine — used by engineers to verify other platforms’ outputs, by utilities reviewing interconnection applications, and by homeowners doing independent checks on installer proposals.

Best for: Independent production verification, utility interconnection reviews, quick feasibility estimates, education and research.

Cost: Free. Available at pvwatts.nrel.gov.

Google Project Sunroof

Google Project Sunroof uses Google Maps satellite and aerial imagery combined with 3D modeling to estimate a home’s solar potential — roof usable area, hours of sunlight per year, and estimated savings. It was a groundbreaking consumer tool when launched in 2015 but has stalled in development. Coverage is still limited to certain US cities, and its production estimates are less detailed than professional tools.

Project Sunroof is useful as a homeowner screening tool — a quick check on whether your roof has solar potential before getting an installer quote. It no longer provides detailed system designs or permit-ready outputs.

Best for: Homeowner initial screening. Not suitable for professional design or permitting.

Cost: Free.

SolarEdge Designer

SolarEdge offers its own free design tool, Designer, optimized for SolarEdge inverter and power optimizer systems. It handles string sizing, power optimizer assignment, panel layout, and generates compatible wiring diagrams. It’s limited to SolarEdge equipment but is free and integrates directly with SolarEdge monitoring and commissioning tools.

Best for: Installers who standardize on SolarEdge equipment. Not suitable for multi-brand or battery-first designs.

Advanced and Specialized Tools

PVsyst

PVsyst is the industry standard for utility-scale and commercial project simulation in Europe, and is widely used by international EPCs and developers worldwide. It offers the most detailed loss modeling of any tool — accounting for spectral effects, soiling, LID (light-induced degradation), non-uniform irradiance, and grid constraints. PVsyst reports are standard requirements for project financing at large European and utility-scale projects.

PVsyst’s interface is less intuitive than newer cloud tools (it’s a Windows desktop application), but its simulation depth is unmatched.

Best for: Utility-scale and large commercial project simulation, project finance requirements, detailed loss analysis, international projects.

Pricing: ~€1,100–€1,500/year depending on license type. Desktop software, not cloud-based.

HOMER Pro (Homer Energy / UL Solutions)

HOMER Pro is not a conventional solar design tool — it’s a microgrid optimization platform. Where Aurora and Helioscope design grid-tied residential and commercial PV systems, HOMER models energy systems with multiple generation sources (solar, wind, diesel, grid), storage, and loads over time. It optimizes component sizing for off-grid, islanded, and hybrid grid systems to minimize cost of energy (LCOE).

Best for: Off-grid systems, remote communities, military microgrids, commercial/industrial facilities with complex backup or resilience requirements, academic research.

Pricing: ~$1,500/year for HOMER Pro. A free version (HOMER Grid) handles simpler grid-connected scenarios.

Solar Design Software Comparison

How to Choose the Right Solar Design Software

The right tool depends on your role and project type:

Residential installer with a sales team: Aurora Solar is the industry standard for a reason — automated roof modeling, integrated proposals, and permit packages justify the cost for companies doing volume residential work. OpenSolar is the best free alternative.

Commercial or utility-scale engineer: Helioscope for US commercial projects; PVsyst for international or large-scale projects requiring bankable simulation reports.

Small installer or startup: OpenSolar’s free tier handles the full professional workflow. Start there, migrate to Aurora when volume justifies the subscription.

Off-grid or microgrid designer: HOMER Pro is the purpose-built tool. No other platform models multi-source energy systems and optimizes component sizing the way HOMER does.

Homeowner verifying an installer’s proposal: Use PVWatts with the system specs from your installer’s proposal to independently verify production estimates. It takes five minutes and uses the same underlying weather data most professional tools rely on.

The Role of AI in Solar Design Software

AI-powered roof modeling has been the biggest platform advancement of the past five years. Earlier tools required installers or engineers to manually trace roof planes from satellite imagery — a process that took 15–30 minutes per project. Current AI engines (Aurora’s most prominent among them) auto-detect planes, ridgelines, and obstructions from satellite and LiDAR data in seconds, with accuracy that often doesn’t require manual correction.

The next frontier is AI-driven permit automation. SolarAPP+ — developed by NREL and adopted by hundreds of US jurisdictions — allows software platforms to auto-generate permit packages that are pre-approved for AHJ compliance without human reviewer intervention. Aurora’s SolarAPP+ integration means that in participating jurisdictions, a permit can be issued the same day as system design.

AI is also entering proposal optimization: some platforms now suggest panel configurations, string layouts, and battery sizing based on the customer’s utility rate structure and load profile, moving toward automated system design rather than just automated drafting.

Frequently Asked Questions

What software do solar installers use to design systems?

Most US residential installers use Aurora Solar for design, proposals, and permit drawings. Helioscope is preferred by commercial and utility-scale engineers for detailed loss modeling. Smaller installers and international companies often use OpenSolar’s free platform. NREL’s PVWatts is universally used for independent production verification.

Is there free solar design software?

Yes. OpenSolar is free for solar professionals and covers the full design-to-proposal workflow. PVWatts (NREL) is free for production estimation. Google Project Sunroof is free for homeowner screening. SolarEdge Designer is free for SolarEdge equipment users. HOMER Grid offers a free version for basic grid-connected microgrid modeling.

How accurate are solar design software production estimates?

Professional tools using NREL TMY weather data are accurate to within 5–10% of actual first-year production for well-modeled systems. Shading is the largest source of error — software models shade from mapped obstructions accurately, but unmodeled obstructions (future tree growth, new construction) aren’t accounted for. Most installers apply a 5% “design contingency” to their production estimates for this reason.

Can homeowners use solar design software?

Homeowners can use Google Project Sunroof for screening, PVWatts for production verification, and OpenSolar’s homeowner-facing tools. Full professional platforms like Aurora require installer credentials. If you want to understand the design your installer produced, ask for their PVWatts or Helioscope report — that’s the most transparent verification of production estimates.

What is the difference between Aurora Solar and Helioscope?

Both are now owned by the same parent company (Aurora Solar acquired Folsom Labs/Helioscope in 2022) but serve different use cases. Aurora Solar is optimized for residential sales workflows — fast AI roof modeling, proposal generation, financing integration, and permit packages. Helioscope is optimized for engineering accuracy — detailed loss tree modeling, string-level electrical analysis, and bankable simulation reports for commercial and utility-scale projects.

Does solar design software include battery storage design?

Yes — most leading platforms now support battery storage design. Aurora Solar handles battery sizing, backup load selection, and financial modeling for solar-plus-storage systems. OpenSolar and Solargraf also support battery configuration. HOMER Pro is the specialized tool for off-grid systems where battery sizing optimization is the primary design objective.

What is SolarAPP+ and how does it relate to design software?

SolarAPP+ (Solar Automated Permit Processing) is an NREL-developed platform that automates permit approval for standard residential solar installations. When a jurisdiction adopts SolarAPP+, installers can submit permit applications directly from their design software (Aurora integrates natively) and receive instant permit approval without waiting for human review. As of 2026, hundreds of US jurisdictions have adopted SolarAPP+, significantly reducing permitting timelines.

Summing Up

Solar design software has removed most of the manual labor from system design, permitting, and proposal generation. Aurora Solar dominates the US residential market with AI-powered roof modeling and integrated workflows. Helioscope remains the engineering standard for commercial and utility-scale simulations. OpenSolar provides a capable free alternative for smaller operations. PVWatts is the transparent, government-backed verification tool every installer and homeowner should know how to use.

For homeowners: understanding what software your installer uses — and asking to see the PVWatts or Helioscope output — is one of the best ways to verify that your system design is accurate and not oversized or undersized for your actual roof and location.

If you’re ready to get a professionally designed solar system for your home, call (855) 427-0058 for a free quote. Our network of vetted installers covers all 50 states and uses professional design tools to model your exact roof, shading conditions, and utility rates before recommending a system size.

Updated August 2026