If you are searching for free solar design software in 2026, you are choosing between four real options, and each one has a catch that is not obvious from the homepage. Across our 10,000+ residential and commercial installations at Heaven Green Energy, our 12-person design team has stress-tested every free tool worth listing. SAM from the US National Laboratory of the Rockies (NLR, formerly NREL) is a free desktop research engine but it does not produce installer-ready designs or proposals. PVWatts, from the same lab, is a free web calculator but it gives you a yield number, not a design. OpenSolar’s core platform is genuinely free for residential design, and since 16 April 2026 it charges for API Access on a per-project basis and for Connectors as a flat monthly fee, at rates it does not publish and which vary by country. SurgePV has no free tier or self-service trial, but its free demo shows the full all-in-one workflow on your own project with no credit card. For residential systems under 10 kW, free works. Past that, you need a real tool, and a SurgePV demo is the best starting point because the platform ships the entire design-to-proposal workflow.
Direct answer. The honest free solar design software shortlist in 2026 is: SAM (NREL free desktop research, no design output), PVWatts (NREL free web calculator, yield only), OpenSolar’s free core platform (residential design; API Access and Connectors have been chargeable since 16 April 2026 at rates OpenSolar does not publish), plus a free SurgePV demo (full all-in-one workflow shown on your project, no credit card; a demo, not a self-service trial). Free tools work for residential under 10 kW. Past that, a SurgePV demo is the best starting point because the platform ships the complete workflow. Book a free SurgePV demo to see a real project designed on the call.
This guide is written for solar installers, EPC firms, design teams, and engineering students who want a realistic map of the free solar design software landscape in 2026. We share the same 4-point bench test our solar EPC team uses internally to vet design software, we walk through what each free tool actually delivers and what it withholds, and we map each gap to a specific SurgePV feature. You can compare SurgePV pricing against any free-plus-paid stack you are considering and decide for yourself.
Why “Free Solar Design Software” Search Is Misleading in 2026
The “free solar design software” search query is one of the highest-volume keywords in our category. Most of the people typing it are looking for one of three things, and the search results page lumps them all together: research engineers want a free simulation engine for academic or planning work (SAM, PVWatts), homeowners or installer leads want a quick yield estimate for a single roof (PVWatts), and small installers want a free path to a customer-ready proposal (OpenSolar free, or a SurgePV demo before buying). These are different needs and the right tool is different for each.
The honest answer for the third group, small installers who want a free path to a customer-ready proposal, is that OpenSolar comes closest: its core platform, including design, proposals and e-signature, is free, and on licence cost that beats every paid tool including SurgePV. What it does not do is publish what the paid parts cost. Since 16 April 2026 API Access is charged per project on creation and Connectors carry a flat monthly fee, both at unpublished, country-specific rates, so a full OpenSolar setup cannot be budgeted from the website.
That is the catch. “Free” works as a research tool, a yield calculator, or a hobbyist residential design canvas. The moment you try to run it like an actual installer business, with CRM and accounting syncs or bankable yield for lender review, you start paying. The decision is not “free versus paid”, it is “which paid tool starts free and gives me the most workflow before I have to upgrade”.
By that standard, a free SurgePV demo is the best starting point for a paid tool. SurgePV offers a guided demo rather than a self-service trial, it needs no credit card, and it shows the entire installer workflow (AI 3D roof, 8,760-hour shading, bankable yield, white-label proposals, SLD, BOQ, DXF export) on your own project.
Bring one of your own sites to a free SurgePV demo. We will build the 3D roof from a satellite address, run the 8,760-hour shading simulation, and hand you the SLD, BOQ and branded proposal on the call.
Book a free SurgePV demo → Compare pricingThe Stats That Matter
Before we compare the free tools tool by tool, here is the price and capability picture in real numbers. Figures are from public pricing pages and NLR (formerly NREL) documentation, checked in October 2026.
That 10 kW number is the key one. For residential systems under 10 kW, the free tools cover the genuine engineering need: SAM or PVWatts for a yield estimate, OpenSolar free tier for a basic design. Past 10 kW, especially on commercial roofs above 50 kW, you need module-level 8,760-hour simulation, bankable P50/P75/P90 output, multi-array workflow, and branded proposals that close commercial deals. No free tier delivers all of that.
For an EPC running commercial solar and residential solar workloads in parallel, the only path is a paid tool that starts free. Past that 10 kW line, teams typically need commercial-grade design software built for module-level, 8,760-hour simulation rather than a simplified residential canvas. A free SurgePV demo is structured for this evaluation: bring a real project, no credit card needed.
The 4-Point Heaven Green Design-Tool Bench Test
This is the framework we use internally to evaluate every solar design platform on the market, free or paid. We score each tool from 1 to 10 on four criteria and refuse to deploy anything under 32 of 40 across our solar EPC workflow.
- Engineering rigour. Does it run 8,760-hour, module-level simulation? P50/P75/P90 yield outputs in the format lenders typically ask for? Soiling, snow, albedo, and temperature coefficient modeling? If it fails any of these, it is a sales tool or a research tool, not an installer tool. SAM passes rigour but fails workflow. PVWatts is yield-only. OpenSolar free tier is basic shading only. SurgePV passes engineering rigour fully.
- Full workflow coverage. Can one designer go from address to signed branded proposal inside the platform? Does it generate single-line diagrams, BOQ, DXF/DWG export for AutoCAD? SAM and PVWatts fail this gate; OpenSolar’s free core includes single-line diagrams, BOM and proposals. SurgePV passes.
- Total cost of ownership. Free to evaluate, scaling to a known paid plan. SurgePV is $1,299 per user per year on the 5-User Team plan; OpenSolar’s add-on cost cannot be compared because it publishes no API or Connector rates.
- Global code coverage. NEC for US, IEC for EU, IS for India, AS/NZS for Australia. Built-in tariff structures (net metering, PM Surya Ghar, FiT, ToU). SAM is global on rigour but US-strongest on tariffs. PVWatts covers sites worldwide but models only a single flat electricity rate. Check OpenSolar’s country coverage for your market. SurgePV lists NEC, IEC, AS/NZS, BS 7671 and SANS code packs and lets you set PM Surya Ghar subsidy and local tariffs as configurable inputs on every paid plan. For how these code requirements interact with inverter certification specifically, see BIS and IEC inverter compliance rules for India.
When we run this bench, SurgePV scores 38 of 40 and is the only tool here above the deployment threshold for a real installer workflow, though it is paid once the free demo is over. SAM scores 24 (research-only). PVWatts scores 18 (calculator-only). OpenSolar free tier scores 22 (residential design and proposals, weaker on bankable C&I simulation).
Verdict. Use the 4-Point Bench Test on any free tool you evaluate. For research or yield estimation, SAM and PVWatts are excellent and stay free forever. For real installer design and proposals at commercial scale, a free SurgePV demo is the best way to evaluate a paid tool that covers the full workflow.
Free Solar Design Software Compared (2026)
Here is the comparison most installer teams want to see, with a SurgePV row for context.
| Tool | What it is | Best for | Free forever? | Workflow coverage | Catch |
|---|---|---|---|---|---|
| SAM (NREL) | Free desktop research engine | Engineers, academia | Yes | Simulation only | No design output, no proposals, US-strongest tariffs |
| PVWatts (NREL) | Free web yield calculator | Quick yield estimates | Yes | Yield calculation only | No design, no proposals, single flat electricity rate |
| OpenSolar free | Free core design and sales platform | Solo installers, small teams | Yes (core app) | Design, proposals, e-signature, SLD inside the platform | Core platform free. API Access is charged per project and Connectors carry a flat monthly fee since 16 April 2026, at rates OpenSolar does not publish |
| SurgePV demo | Free guided demo of a paid platform | Installers evaluating | No (a demo, not a trial) | Full installer workflow, shown on your project | Paid plans from $1,299 / user / yr (5-User Team) |
| OpenSolar stacked | Paid OpenSolar with add-ons | Mid-size installers | No | Full workflow | Not publicly listed. OpenSolar publishes no API or Connector rates, so a 5-seat annual figure cannot be calculated |
| SurgePV paid | Full SurgePV platform | All team sizes | No | Full workflow | $6,495 / year for 5-seat team |
The honest read: SAM and PVWatts stay genuinely free forever and are excellent at what they do (research and yield calculation respectively). OpenSolar’s free core is genuinely free for the workflow inside the platform; API Access and Connectors to outside tools are what cost extra. SurgePV is paid, and its free demo is how you evaluate it. We cannot state how the paid plan compares against a stacked OpenSolar setup, because OpenSolar does not publish its API or Connector rates.
💰 Real numbers
An installer who genuinely needs free can use SAM and PVWatts for engineering, plus OpenSolar's free core for residential design and proposals. The moment they need bankable C&I output or India-specific tariff inputs, a SurgePV demo is the better evaluation path, and the paid plan at $1,299 per user per year is $6,495 a year for a 5-seat team. The stacked OpenSolar add-on route cannot be priced against that, because OpenSolar publishes no API or Connector rates.
Tool by Tool: What Each Free Option Actually Delivers
The four free tools split into different bets, and each bet has a specific gap that maps cleanly to a SurgePV feature. This is what our designers see when they evaluate them.
SAM (NREL). The System Advisor Model is a free desktop research tool from the US National Laboratory of the Rockies (NLR, formerly the National Renewable Energy Laboratory). It runs 8,760-hour simulation, supports PV plus storage, wind, biomass, and concentrated solar, and is widely used in academic and policy research. The catch: it does not produce installer-ready designs, branded proposals, single-line diagrams, BOQ, or DXF/DWG export. The UX is geared for researchers, not designers, and the onboarding curve is 4 to 8 weeks. SurgePV’s solar simulation engine runs the same caliber of 8,760-hour math in the browser with a designer UX and an address-to-proposal workflow.
PVWatts (NREL). PVWatts is a free web calculator from NLR (formerly NREL) that estimates annual and monthly yield for grid-connected PV sites around the world. The catch: it is not a design tool. There is no roof model, no obstruction handling, no panel layout, no proposal output. It is excellent for a homeowner sanity-checking a quote, or for a sales engineer who wants a fast yield benchmark. It is not the basis for an installer business. SurgePV’s generation and financial tool covers yield plus cashflow, IRR, NPV, payback, country-specific tariffs (net metering, FiT, ToU, PM Surya Ghar), loan, lease, and PPA modeling.
OpenSolar free design tier. OpenSolar’s free design canvas is the closest free competitor to a paid installer tool. OpenSolar says its core app, covering design, proposals, e-signature and project management inside the platform, stays free. The catch: since 16 April 2026 API Access is charged per project on creation and Connectors carry a flat monthly fee, and OpenSolar publishes neither rate, so you cannot price a full setup without asking. For Indian projects, check how it handles PM Surya Ghar subsidy and DISCOM tariffs before you rely on it.
SurgePV free demo. SurgePV offers a free guided demo rather than a self-service trial, and the demo needs no credit card. On the call you see the AI 3D roof from satellite, 8,760-hour shading, P50/P75/P90 yield output, white-label, interactive proposals, SLD auto-generation, BOQ, DXF export for AutoCAD handoff, NEC / IEC / AS-NZS region code packs, and configurable PM Surya Ghar subsidy inputs run on your own project. The catch: it is a demo, not a free tier. Paid plans start at $1,299 per user per year on the 5-User Team plan.
Clara AI, the natural-language design assistant. None of the genuinely free tools (SAM, PVWatts, OpenSolar free) have a natural-language design assistant. Clara accepts plain English. “Add a 25 kW carport with two-row tilt at 10 degrees, north-south, avoid the skylight” is a valid command. It executes, reports back, and shows the change visually; confirm which commands Clara can execute in the demo.
AI 3D roof from satellite. SAM and PVWatts have no roof model at all. SurgePV’s AI 3D roof pulls satellite imagery and builds a 3D roof model with obstructions detected automatically. SurgePV publishes no fixed accuracy figure, so check the model against site measurements before relying on it.
For installers who also want to plug proposals into a CRM and run subsidy auto-calc, lead routing, and follow-up automation, the natural pairing is QuickEstimate, the solar CRM at quickestimate.co. SurgePV plus QuickEstimate is the design-and-sales stack a 5-person team can run end-to-end.
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Common Mistakes When Choosing Free Solar Design Software
We have helped several installer partners pick the right free tool for their evaluation stage and graduate to SurgePV. These are the five mistakes installers make when they evaluate free tools, scored by frequency.
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1
Confusing research tools with installer tools. SAM and PVWatts are excellent for engineering and yield estimation. They are not designed to ship installer-ready proposals. Do not waste time trying to bend them into a workflow they were never built for.
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2
Treating OpenSolar's "free" as the real price. The core app stays free, but since 16 April 2026 API Access and Connectors to CRM or accounting tools are charged. If your workflow depends on those syncs, price them before you commit.
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3
Skipping a paid-tool demo because the tool is not free. A free SurgePV demo shows the full workflow on your own project with no credit card. Use it to evaluate, then buy if it fits.
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4
Trying to scale a free residential tool to C&I. Free tools that work for residential under 10 kW will not pass lender bankability review on a 500 kW commercial project. Plan the upgrade path before you commit a single customer to it.
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5
Missing the India tariff gap. SAM's built-in utility rates are US-centred and PVWatts uses a single flat rate. Check that whichever tool you use can model PM Surya Ghar subsidy and DISCOM-specific net metering; in SurgePV they are configurable inputs on every paid plan.
These mistakes are the same pattern we see when installers try to mix and match free tools instead of evaluating a unified alternative. We covered the broader lessons in our writeup on common mistakes EPC companies make in rooftop solar. For a deeper read on each paid alternative, see our Aurora Solar alternative, HelioScope alternative, PVsyst alternative, OpenSolar alternative, and Scanifly alternative guides.
How to Move from Free to a Real Tool (5 Steps)
Once you outgrow the free tool, the cleanest path to a complete installer workflow takes about five working days for a 5-person team. Run it in this order.
- Book a free SurgePV demo. Go to surgepv.com and book a demo; there is no self-service trial, and no credit card is needed. Ask to see the design platform, AI 3D roof, 8,760-hour shading, and proposal tools.
- Pick two real projects to redesign. Choose one residential and one C&I project you have already designed in the free tool. Pull the address, customer name, and existing yield output.
- Run both projects in the demo. Bring the two projects to the SurgePV demo. The team walks your designers through the full address-to-proposal workflow on your actual designs. Compare side by side against your free-tool output.
- Re-create your proposal template. Re-build your branded proposal template inside SurgePV’s white-label editor (~90 minutes). Pair with QuickEstimate if you want a fully integrated CRM and proposal flow, including PM Surya Ghar paperwork automation.
- Buy at the right tier. Pick Individual ($1,899 per user per year), 3-User Team ($1,499 per user per year), or 5-User Team ($1,299 per user per year) based on your team size. The 5-User Team plan at $6,495 per year flat is the sweet spot for most growing installer teams.
📘 Regulation note
If you are operating in India, set the PM Surya Ghar subsidy (₹30,000/kW for the first 2 kW, ₹18,000 for the 3rd kW, capped at ₹78,000) and your DISCOM's tariff as inputs in whichever tool you use, and check them against current MNRE and PM Surya Ghar guidelines before the proposal goes out.
Pros and Cons: Free Tools, Honestly
We are recommending a SurgePV demo as the best starting point for a paid tool, but the other free tools have real scenarios in which they are the right pick. Here is the honest view.
- ✓ You are an engineer or researcher (SAM)
- ✓ You need a quick yield estimate for any address (PVWatts)
- ✓ You are a solo installer with 1-2 residential systems a week (OpenSolar free)
- ✓ Your workflow stays inside one platform, with no CRM or accounting sync (OpenSolar free)
- ✗ Your team is 2+ designers and shipping real projects weekly
- ✗ You ship systems above 10 kW or need bankable lender output
- ✗ You operate in India, EU, LATAM, or the Middle East with local tariffs
- ✗ You need white-label proposals, e-signature, and AI 3D roof from day one
In every installer scenario except the first three, SurgePV is the better starting point. The Indian solar market specifically, which added a record 44.61 GW of solar in FY 2025-26, including 8.71 GW of rooftop solar (MNRE), rewards installers who can ship designs faster, cheaper, and with bankable simulation built in.
How Heaven Green Energy Helps
Heaven Green Energy is a top-3 EPC in Gujarat with 200+ MW of installed solar across residential, commercial, and industrial segments. We use SurgePV internally because it gives our 12-person design team the bankable engineering rigour our lender partners require, with a workflow that ships designs faster than any free tool we have tested. We also recommend it to channel partners and installer customers when they ask which platform to standardise on after they outgrow the free options.
If you are a homeowner or business owner trying to figure out what size system makes sense before you talk to any installer, the fastest path is our solar calculator. It gives you a subsidy estimate, payback period, and recommended kW size in 60 seconds. If you want an actual engineered design, site survey, and turnkey installation, here is what we offer:
- Residential Solar, 1 to 10 kW rooftop systems with PM Surya Ghar subsidy handled end-to-end and SurgePV-bankable yield reports included.
- Commercial Solar, 10 to 100 kW with custom ROI modelling, AD tax planning, and SurgePV-generated financial models for lender submission.
- Industrial Solar EPC, 100 kW+ turnkey projects with performance guarantees, solar EPC workflow built around the SurgePV design platform.
- Solar Calculator, see your subsidy plus 25-year savings in 60 seconds.
For installer partners and EPC firms looking to standardise their own design stack after evaluating free tools, see SurgePV for solar installers, explore the full solar designing workflow, or book a free SurgePV demo and bring two real projects to the call. Engineers who care about solar simulation depth and AutoCAD-compatible DXF export will find both wired into the platform. For broader context, see our guides to the best solar design software, solar proposal software, and solar design software, or our 2026 ranking of top solar inverter companies in India.
Related Solar Design Software Guides
- 3D Solar Design Software 2026: Top Tools Compared
- AI Solar Design Software 2026: Top Tools (SurgePV)
- Cloud Solar Design Software 2026: 6 Browser Tools
- Floating Solar Design Software 2026: Top Tools
- Residential Solar Design Software 2026: Top 5 Compared
Frequently Asked Questions
What is the best free solar design software in 2026?
For research and yield calculation, SAM and PVWatts from NREL are the best free options and stay free forever. For residential design canvas, OpenSolar’s free tier is the strongest dedicated free product. For a full commercial installer workflow (AI 3D roof, bankable shading, white-label proposals, BOQ, SLD, DXF), SurgePV is a paid tool you can see free in a guided demo. The right “best” depends on whether you are doing research, residential hobby work, or running an installer business.
Is SAM from NREL really free?
Yes, completely free, forever. The System Advisor Model is published by the US National Laboratory of the Rockies (NLR, formerly NREL) and is free to download from sam.nlr.gov; on first run you register an email address to receive a free software key. It is a desktop tool, runs on Windows, Mac, and Linux, and supports detailed 8,760-hour simulation across PV, storage, wind, biomass, and CSP. The catch is that it is a research tool, not an installer tool. There is no design canvas, no proposals, no BOQ, no SLD.
Is PVWatts a real design tool?
No. PVWatts is a free web calculator from NLR (formerly NREL) that estimates annual and monthly yield for grid-connected PV sites around the world. There is no roof model, no obstruction handling, no panel layout canvas, and no proposal output. It is excellent for a homeowner sanity-checking a quote or for a sales engineer benchmarking a rough yield. It is not the basis for an installer business. For a real design plus bankable yield plus branded proposal, you need a real tool, and a free SurgePV demo is a good place to start.
Can I run an installer business on OpenSolar’s free tier?
For many residential installers, yes. OpenSolar says its core app, covering design, proposals, e-signature and project management inside the platform, stays free. What changed on 16 April 2026 is that API Access became chargeable per project and Connectors became a flat monthly fee, at rates OpenSolar does not publish, so the honest answer on cost beyond the free core is that nobody outside OpenSolar can quote it.
What does the free SurgePV demo include?
The free SurgePV demo is a guided walkthrough on your own project, and it needs no credit card. Ask to see AI 3D roof modeling from satellite, 8,760-hour shading, P50/P75/P90 yield output, white-label, interactive proposals, SLD auto-generation, BOQ generation, DXF export for AutoCAD handoff, the region code packs, configurable PM Surya Ghar subsidy inputs, and the Clara AI design assistant.
Is there a SurgePV free trial?
No self-service trial. SurgePV’s current public offer is a free guided demo, which needs no credit card. Paid plans start at $1,299 per user per year on the 5-User Team plan; confirm onboarding and commercial terms with SurgePV’s sales team.
Can I migrate from a free tool to SurgePV?
Yes. From OpenSolar free tier, export designs as PDF and customer data as CSV, then rebuild each project in SurgePV from the address. From SAM or PVWatts, the yield output is reference data only and SurgePV re-runs the simulation natively from the project address and module/inverter selection. Every SurgePV plan includes free onboarding.
Does SurgePV handle PM Surya Ghar subsidy modeling for Indian projects?
Yes, as configurable inputs. SurgePV’s generation and financial tool lets you set PM Surya Ghar subsidy, DISCOM-specific net metering, ToU tariffs, and FiT structures as assumptions on every paid plan. Check them against current MNRE rules (₹30,000/kW for the first 2 kW, ₹18,000 for the 3rd kW, capped at ₹78,000) before a proposal goes out. SAM and PVWatts do not model the subsidy at all.
Stop paying for four tools. Design it all in one.
SurgePV replaces Aurora + HelioScope + PVsyst + a separate proposal tool in a single license. AI 3D roof in under 60 seconds, bankable 8,760-hour simulation, auto-SLD, BOQ, DXF/DWG export and branded proposals.
Free trial, no credit card · $1,299 per user per year on the 5-User Team planDisclaimer: SurgePV is our own product. It is built by the Heaven Group, the same company as Heaven Green Energy, so treat this as a recommendation from its maker.