“Free solar design software” gets searched 600+ times per month in the US alone. Most of the tools that show up under that query are either: (a) genuinely free with significant limits, (b) free trials of paid software, or (c) “free” but require paid AutoCAD/separate tools to actually complete a workflow. This guide separates the three. See Agricultural Solar Design for more. See Air Source Heat Pump Solar PV Sizing for more.
What “Free” Actually Means in Solar Design Software
Before listing tools, the four real models you’ll encounter: See Albedo Values for Solar Design for more. See Battery Solar System Design UK for more.
- Genuinely free forever — no per-seat fees, no contracts. Funded by partner integrations or freemium upgrades. (OpenSolar, SAM)
- Free trial, then paid — full features for 14-30 days, then license required. (PVsyst, Aurora, HelioScope, SurgePV)
- Free tier with hard caps — works free up to a limit (system size, projects per month, features), then paid upgrade. (Many)
- Free as a marketing channel — looks free until you hit AutoCAD requirements, separate proposal tools, or financial modeling that aren’t included. (Most “free” CAD-based tools)
The honest answer: there are exactly two genuinely-free production-ready solar design tools (OpenSolar and SAM). Everything else is one of the other three categories. See Best Direction for Solar Panels in [Complete Guide] for more.
The 7 Best Free Solar Design Software
1. OpenSolar — Best Genuinely Free for Residential
Best for: Pure residential installers (under 500 kW) who don’t need US SLD generation.
OpenSolar is genuinely free for the core platform — no per-seat fees, no contracts, unlimited users. Includes design canvas, proposals, e-signatures, payments processing, and CRM. 28,000+ users in 185 countries. Funded by module manufacturers, financiers, and other industry partners (which is also the catch).
What’s free: Core design + proposals + CRM + e-signatures, unlimited users. What’s not free: US SLD generation requires AutoCAD, which is licensed separately, HD Premium Imagery bundle (custom pricing). Caps: 500 kW project limit (performance issues above), one module manufacturer per project. Catch: Partner-funded business model means project data flows to partners by design.
2. SAM (System Advisor Model) — Best Free for Engineering Analysis
Best for: Engineers, researchers, and consultants needing rigorous yield + financial modeling.
SAM is NREL’s free open-source tool covering yield simulation, financial modeling (cash flow, NPV, IRR), and multiple system types (PV, CSP, battery, geothermal). Engineering depth is real — it’s used in academic research and bankability analysis. Catch: no design canvas, no proposals, dated UI.
What’s free: Full simulation engine + financial modeling + open-source code. What’s not free: Nothing — actually free. Caps: No project limits, no system size limits. Catch: No layout canvas, no customer-facing proposals, no integration with other tools.
3. PVWatts (NREL) — Best for Quick Yield Estimates
Best for: Quick “is this site viable?” yield estimates without deep simulation.
PVWatts is NREL’s free web-based tool for estimating PV system yield from location, system size, and basic settings. It’s not a design tool — it’s a yield calculator. Useful for site screening and customer education.
What’s free: Yield estimation for any global location, basic financial calculation. What’s not free: N/A Caps: No layout, no proposals, no string design — yield estimation only. Catch: Output is too basic for production proposal use; pair with another tool for actual design.
4. PVsyst Free Trial — Best Free Trial for Bankability
Best for: Engineers evaluating PVsyst for utility-scale work.
PVsyst offers a 30-day free trial with full features — no restrictions, no watermarks during trial. After 30 days, reports become watermarked in DEMO mode unless you license the software. PVsyst does not publish list pricing on its own website.
What’s free: 30 days of full PVsyst access. What’s not free: Beyond 30 days, license required. Caps: Trial is time-limited; PVsystCLI has separate 250-execution / 60-day trial. Catch: Standard PVsyst limitations apply (Windows-only, simulation-only, 4-6 week learning curve).
5. SurgePV Free Trial — Best Free Trial for All-in-One
Best for: Teams evaluating an integrated design + simulation + proposal + financial modeling platform.
SurgePV offers a free trial with full platform access. Unlike many trials, the trial includes design canvas, simulation, proposal generation, and financial modeling — the complete workflow rather than a stripped-down preview.
What’s free: Full platform during trial period (browser-based, any OS). What’s not free: Beyond trial, custom organizational pricing. Caps: Trial is time-limited. Catch: None for evaluation — production use requires a paid plan.
6. Aurora Solar — Subscription Only, No Free Tier
Best for: Designers who want Aurora’s quality and can commit to a per-user subscription.
Aurora doesn’t publicly advertise a standard free trial. Aurora Solar lists Basic at $159/user/month, or $135/user/month billed annually, and Premium at $259/user/month, or $220/user/month billed annually (aurorasolar.com/pricing, checked 21 September 2026). Enterprise is custom per project, contact sales.
What’s free: N/A. What’s not free: The whole platform, on a per-user subscription. Caps: Plan features vary by tier. Catch: No free tier, so evaluation runs through a guided demo.
7. HelioScope Free Trial — Best Free Trial for C&I Simulation
Best for: C&I designers evaluating HelioScope’s DNV GL-validated simulation accuracy.
HelioScope offers a free trial period with full Pro features. After trial, a paid plan is required. HelioScope lists Basic at $159/month or $1,620/year per licence and Pro at $259/month or $2,640/year per licence (helioscope.aurorasolar.com/pricing, checked 21 September 2026).
What’s free: Trial period with full features. What’s not free: Beyond trial, Basic $159/month or $1,620/year per licence, Pro $259/month or $2,640/year per licence (helioscope.aurorasolar.com/pricing, checked 21 September 2026). Caps: 10 projects/month on Basic and Pro tiers; 15 MW system size hard limit. Catch: Project caps continue to apply post-trial.
Free Solar Design Software — Quick Comparison
| Tool | Truly Free? | What’s Included | Hidden Costs | Best For |
|---|---|---|---|---|
| OpenSolar | ✅ Forever | Design + proposals + CRM | AutoCAD for US SLD, licensed separately | Pure residential under 500 kW |
| SAM (NREL) | ✅ Forever | Simulation + financial modeling | None | Engineering analysis |
| PVWatts (NREL) | ✅ Forever | Yield estimation only | None | Quick site screening |
| PVsyst Trial | 🟡 30 days | Full PVsyst features | Then a licence; PVsyst does not publish list pricing | Trial bankability |
| SurgePV Trial | 🟡 Trial period | Full platform | Then custom pricing | Trial all-in-one |
| Aurora Solar | 🔴 Paid | Per-user subscription | Basic $159/user/mo, $135/user/mo billed annually; Premium $259/user/mo, $220/user/mo billed annually (aurorasolar.com/pricing, checked 21 September 2026) | Per-user Aurora use |
| HelioScope Trial | 🟡 Trial period | Full features | Then Basic $159/mo or $1,620/yr per licence, Pro $259/mo or $2,640/yr per licence (helioscope.aurorasolar.com/pricing, checked 21 September 2026) + caps | Trial C&I simulation |
When Free Solar Design Software Makes Sense
Use OpenSolar (free) if:
- You’re 100% residential under 500 kW
- You don’t need US single-line diagrams (or you already have AutoCAD)
- Partner-funded data model is acceptable
- You don’t need utility-scale work
Use SAM (free) if:
- You’re an engineer/researcher needing rigorous yield + financial analysis
- You don’t need a design canvas or customer-facing proposals
- You’re comfortable with technical command-line tooling
Use PVWatts (free) if:
- You need a 5-minute “is this viable?” yield estimate
- You’re paired with another tool for actual design
When Free Doesn’t Work
Free tools break down when:
- Your pipeline includes commercial work above 500 kW — OpenSolar caps; SAM has no design canvas
- You need US SLD generation — Both OpenSolar and SAM require AutoCAD, which is licensed separately
- You need integrated proposals and financial modeling — SAM has no proposals; OpenSolar has them but limited
- You’re scaling past 5+ designers — Free tools work for individuals but team collaboration is limited
- You need utility-scale work — Free tools either cap (OpenSolar 500 kW) or lack the layout canvas (SAM, PVWatts)
For these use cases, an integrated paid platform can be simpler to run, because the alternative is OpenSolar plus AutoCAD plus a separate commercial tool plus a separate proposal tool, each licensed on its own.
Free Software vs Paid: The Real Math
For a typical 3-designer commercial EPC team:
| Stack | Licensing Structure | Limits |
|---|---|---|
| OpenSolar (free) + AutoCAD + commercial tool | Three tools, two of them licensed separately | Multiple tool integration overhead, 500 kW cap on free tier |
| SAM (free) + CAD + proposal tool | Three tools, two of them licensed separately | No layout canvas, manual workflow stitching |
| All-paid integrated platform (SurgePV-class) | One subscription | Single workflow, no caps |
Free tools are genuinely free for individuals and pure residential. For multi-designer commercial teams, a free design tool still has to be paired with separately licensed CAD and proposal tools, so compare the whole stack rather than the headline price.
Where SurgePV fits
For the product-side detail, SurgePV residential design covers the workflow, outputs and limits.
Frequently Asked Questions
What is the best free solar design software in 2026?
OpenSolar is the most capable genuinely-free solar design tool because it includes 3D modeling, shading analysis, and proposal generation without project caps or feature locks. SAM (System Advisor Model) is the best free option for performance simulation but lacks design and proposal features. PVWatts is best for quick yield estimates only.
Is OpenSolar really free forever?
Yes — OpenSolar’s core platform is free for solar installers with no project limits. It monetizes through hardware partner referrals (panels, batteries, inverters) and an optional paid Pro tier for enterprise features. Independent installers can run their full business on the free version.
Can SAM design a rooftop solar system?
Not the way Aurora or SurgePV can. SAM is a simulation engine, not a design tool — you define system parameters (capacity, tilt, azimuth, location) and it produces hourly performance output. Use SAM after another tool defines the layout, not as a replacement for design software.
Is PVsyst free?
No, PVsyst is paid software. There is a 30-day free trial, but full use requires a licence. PVsyst does not publish list pricing on its own website. PVsyst is the gold standard for bankable simulations but is not in the “free” category.
What are the limitations of free solar design tools?
Free tools typically have one or more of these gaps: no automated proposal generation (you build PDFs manually), no CRM or pipeline tracking, limited customer-facing tools (no signature capture, no payment links), and constrained support. Free tools work for solo installers but rarely scale past 50-100 projects/year.
Do free solar design tools work for commercial projects?
For small commercial (under 100 kW), yes — OpenSolar and HelioScope free trials can handle the design. For larger commercial (multi-MW), free tools fall short: you’ll need ground-mount layout tools, advanced shading from LiDAR, and bankable yield reports that free platforms don’t produce. Plan for paid software at scale.
Recommended Next Step
If you’re evaluating free solar design software but expect to outgrow it within 6-12 months, save the migration pain and start with a tool that scales. Book a 20-minute SurgePV demo to see how the all-in-one workflow compares to OpenSolar + auxiliary tools — and you can compare against your free-tool baseline directly.
For pure residential installers staying under 500 kW with no commercial pipeline, OpenSolar’s free tier remains the best starting point.
