Most software reviews start by looking for something to criticise. This one cannot honestly do that, because SAM is free, built by a national laboratory, and very good at its job. So the review has to ask a harder question instead. Not “is SAM good”, but “is SAM the thing an installer should be running on Monday morning”. Those are different questions, and confusing them costs real teams real money.
Direct answer. SAM, the System Advisor Model from NREL, is a free desktop tool for techno-economic modelling of renewable energy systems. It is outstanding for financial modelling, technology comparison, and sensitivity analysis. It does not produce roof layouts, 3D near-shading scenes, drawing sets, or customer proposals. Download SAM for the analysis. Run SurgePV for the production workflow. They are complements, not rivals.
TL;DR
- SAM is free, developed by NREL, and genuinely excellent for techno-economic analysis across PV, CSP, wind, and storage.
- Its strongest ground is financial modelling, technology comparison, and sensitivity analysis. Nothing commercial matches it there for the price.
- It is not a layout tool. No roof layout, no 3D near-shading scene, no drawing production, no customer proposal.
- The learning curve is steep, and the intended user is an analyst rather than an installer.
- SurgePV covers design, module-level shading, single-line diagrams, DWG export, and white-label proposals in one licence at $1,299 to $1,899 per user per year.
What SAM Is and Who It Is Really For
SAM stands for System Advisor Model. It is a desktop application from the US National Renewable Energy Laboratory, and its purpose is techno-economic modelling of renewable energy systems. It covers photovoltaics, concentrating solar power, wind, storage, and more besides.
The word to hold onto is “techno-economic”. SAM models the technology and the money together. You describe a system, a resource dataset, and a financial structure, and SAM tells you what the economics look like over the project life.
The intended user is an analyst. Someone in a research group, a policy shop, a utility planning team, or a developer’s early-stage feasibility desk. That person asks questions like “does a battery pencil at this tariff” or “how does the return move if module cost drops 15 percent”. SAM answers those questions extremely well.
The person SAM was not designed for is the installer with a site visit at nine and a permit deadline at five. That is a statement of scope, not a criticism.
What Free Actually Means Here
SAM is free, and the reason matters more than the price.
Commercial solar software is free for one of two reasons. Either it is a stripped tier designed to push you toward a paid plan, or the vendor monetises you somewhere else. Neither applies to SAM. It is funded as public research infrastructure by a national laboratory, and NREL has no product to upsell you.
That changes how you should read the outputs. There is no vendor motive nudging a yield number up or a cost assumption down. The assumptions are published, the models are open, and the incentive to flatter a result simply is not present. For anyone who has watched a sales-oriented tool quietly produce a generous production estimate, that neutrality is worth a lot.
It also means the roadmap follows research priorities rather than support tickets. That is right for a research tool and wrong as an assumption for a production workflow, which is the whole tension in this review.
What SAM Does Better Than Any Commercial Tool
This section deserves to be generous, so here it is without hedging.
Techno-economic modelling. SAM ties the physical system to the financial structure in one model. Cash flows, incentives, depreciation, debt, and project return all sit next to the energy model rather than in a separate spreadsheet. Very few commercial design tools attempt this at all, and the ones that do treat it as a bolt-on.
Technology comparison. SAM covers PV, CSP, wind, and storage inside one application. If the real question is whether a site wants solar, solar plus storage, or something else entirely, SAM lets you ask it without buying four tools. That breadth is rare and it is genuinely useful at the feasibility stage.
Sensitivity analysis. This is where SAM earns its reputation. You can sweep an input across a range and watch the economics respond. Which assumption actually drives the outcome? SAM answers that directly, and knowing the answer changes how you negotiate a contract or price a bid.
Credibility and transparency. The output carries the weight of a national laboratory, and in academic work, policy analysis, and early-stage feasibility that provenance is understood and accepted. Assumptions are visible and adjustable, and the models are open, so an analyst can audit the path from input to result.
If your question is whether a technology and a financial structure are viable, SAM is the strongest free answer available and probably the strongest answer at any price.
What SAM Deliberately Does Not Do
The limits are scope decisions, not defects. SAM never claimed this ground.
It is not a layout tool. There is no detailed roof layout. You do not trace roof planes, place modules around obstructions, or resolve setbacks. SAM takes a system description, not a drawing of a specific building.
There is no 3D near-shading scene. You cannot build the neighbour’s chimney, the parapet, and the rooftop HVAC unit as geometry and let the model resolve their shadows through the year from a real obstruction survey.
It produces no drawing set. No single-line diagram for the permit package, no DWG for the drafter, no layout sheets for the crew. Drawing production happens entirely elsewhere.
It produces no customer proposal. There is no branded, customer-facing document with your logo and a savings narrative. Nobody signs a SAM output.
The learning curve is steep. SAM is aimed at analysts, and the interface assumes you already understand the modelling vocabulary. A new user does not become productive in an afternoon.
Read that list and the shape becomes clear. SAM answers a question about viability. An installer’s day is a question about specificity.
SAM vs SurgePV, and Why That Framing Is Slightly Wrong
Let me set up the table honestly. SAM and SurgePV are not competitors. They answer different questions for different people at different points in a project. The comparison below is about fit, not about which one wins.
SurgePV is a browser-based solar design platform. It runs 8,760-hour simulation with module-level shading, mismatch, and string topology. It produces single-line diagrams and DWG export from the same model, plus a white-label proposal layer, in one licence at $1,299 to $1,899 per user per year.
| The job | SAM (NREL) | SurgePV |
|---|---|---|
| Primary question answered | Is this technology and financial structure viable? | What exactly goes on this roof, and what do I hand over? |
| Intended user | Analyst, researcher, policy team, feasibility desk | Installer, EPC designer, proposal engineer |
| Techno-economic and cash flow modelling | Core strength | Not the same purpose |
| Technology comparison across PV, CSP, wind, storage | Yes, in one tool | PV design focused |
| Sensitivity analysis | Core strength | Not the same purpose |
| Detailed roof layout | Not provided | Yes |
| 3D near-shading from an obstruction survey | Not provided | Module-level shading and mismatch |
| Hourly 8,760 simulation | Yes | Yes |
| String topology modelling | Not a layout-level concern | Yes |
| Single-line diagram | Not provided | Produced from the same model |
| DWG export | Not provided | Produced from the same model |
| White-label customer proposal | Not provided | Included |
| Delivery | Windows-oriented desktop application | Browser-based |
| Price | Free | $1,299 to $1,899 per user per year |
The table has no losing column. It has two tools pointed at different halves of a project. If you read it as a scorecard you have misread it.
The Trap of Running Production Work on a Research Tool
Here is the genuine warning, and it is the only real criticism in this review. It is not a criticism of SAM at all.
Because SAM is free and carries a national laboratory’s name, teams reach for it as the foundation of their workflow. The logic feels sound. The tool is authoritative, the price is zero, and the production number looks defensible. So the company standardises on it.
Then the mechanism kicks in. A designer models the system in SAM and gets a credible annual figure. Now the permit set is due, so a drafter opens AutoCAD and builds the array from scratch: module positions, setbacks, string runs, equipment locations, none of which existed in SAM. Then sales needs something to send the customer, so a coordinator retypes the production number, the system size, and a screenshot into a template deck or a proposal platform.
Count what happened. The array was described once in a tool that never held its geometry, then constructed twice by hand in tools that never saw the simulation. Nothing propagates. Change the string configuration and three artefacts disagree until somebody notices, usually the AHJ or the customer.
Put a number on it. Call it 90 minutes per project to build the layout by hand and reconcile the proposal against the model. At 150 projects a year that is 225 hours, well over a month of skilled time, spent recreating information the workflow should have carried forward.
The free tool cost nothing. The workflow around it cost a salary.
Try the software behind this review
Keep SAM for the analysis. Run the production work in a browser.
SurgePV runs 8,760-hour simulation with module-level shading, mismatch, and string topology, then produces the single-line diagram, the DWG, and the white-label proposal from the same model. One licence, one array, one number.
Book a free SurgePV demo →No credit card. 20-minute walkthrough on one of your own projects.
Who Should Use Which, and When to Use Both
Download SAM if you evaluate technology tradeoffs, model financial structures, or need to know which assumption drives a return. It is free, so there is no procurement argument to have. Any installer curious about whether storage pencils on a given tariff should spend an evening with it.
Run SurgePV as the daily driver if your job is to put modules on a specific roof and hand something to a customer and an inspector. SurgePV runs 8,760-hour simulation with module-level shading, mismatch, and string topology, then produces the single-line diagram, the DWG export, and the white-label proposal from that same model.
Keep PVsyst as well if a lender or independent engineer reviews your yield. That remains the reference for financed work, and the distinction between the two engines is covered in PVsyst vs SAM for bankable yield.
Use both SAM and a design platform if you do feasibility work ahead of design. SAM tells you whether the project is worth designing. The design platform tells you what to build. That sequence is coherent, and neither tool resents the other.
If your bottleneck is drawing production rather than software, our solar rooftop detailed engineering design team produces the full construction pack. See the sample design pack or talk to our team.
What Most Buyers Get Wrong About Free Research Software
They read “free” and “national laboratory” as a signal of completeness.
The reasoning is understandable. If a serious institution gives away a serious tool, the tool must cover the serious work. But research software is scoped to a research question, and completeness was never the goal. NREL built SAM to answer viability questions rigorously. It did not build SAM to get a permit approved in Fresno.
Here is the concrete mechanism. A team adopts SAM as the standard, so the design step has no owner. Layout drifts to whoever has AutoCAD open. Shading becomes a judgement call rather than a modelled result from a real obstruction survey. The proposal becomes a slide deck maintained by hand. None of these gaps announce themselves, because each one gets filled by a person rather than a tool.
Six months later the company has three sources of truth and no idea which one the customer was shown. That failure did not come from SAM. It came from asking a research tool to be a production system.
The Verdict
SAM is excellent, free, and not your production workflow. All three statements are true at once.
If your question is techno-economic, SAM is the strongest tool you can obtain at any price, and its provenance means the numbers arrive without a vendor’s thumb on the scale. Download it. Learn it if you have the patience for the learning curve. It will make you better at judging which projects deserve engineering time.
Here is the opinionated call. If you install solar for a living and you are treating SAM as your design tool, you are not saving money, you are moving the cost from a licence line to a payroll line where nobody measures it. The layout, the shading scene, the drawing set, and the proposal all still have to exist. Right now people are making them by hand.
Run SurgePV for the production workflow at $1,299 to $1,899 per user per year, keep SAM open for the feasibility and sensitivity questions, and add a PVsyst seat if a lender reviews your yield. That combination is honest about what each tool is for. If you want the wider commercial field ranked, our PVsyst alternatives guide covers it, and the per-seat numbers sit in the solar design software pricing breakdown.
Conclusion
- SAM is a genuinely excellent public research tool and deserves the respect. For techno-economic modelling, technology comparison, and sensitivity analysis, it is the best free option in the industry.
- It is not a competitor to a design platform, it is a complement. SAM answers whether a project is viable. A design tool answers what goes on the roof and what the customer signs.
- The real risk is running production work on a research tool. Layout, drawings, and proposals then get rebuilt by hand, and that labour costs far more than any licence.
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Disclosure and accuracy note
Commercial relationship. Heaven Designs and SurgePV are part of the same group. Treat our recommendation of SurgePV as a vendor making its own case, not an independent verdict. We have tried to describe every other product fairly, and to say plainly where a competitor is the better choice.
Pricing. All prices are indicative, compiled from public sources when this page was written. They vary by tier, region, contract term and exchange rate, and change without notice. Several vendors quote rather than publish, and some price in currencies other than the US dollar, so a converted figure moves with the exchange rate. Confirm current pricing with the vendor before you decide anything.
Trademarks and corrections. All product names and trademarks belong to their respective owners, and are used here for identification and comparison only. Their use does not imply affiliation with or endorsement by those companies. If anything here is out of date or wrong, tell us and we will correct it.
FAQ
Is SAM from NREL any good? Yes, genuinely. It is a serious techno-economic modelling tool from a national laboratory, strong on financial modelling, technology comparison, and sensitivity analysis, and widely used in academia, policy analysis, and early-stage feasibility. It is free, and there is no vendor motive shaping the results.
Can SAM design a solar rooftop layout? No. SAM does not do detailed roof layout, and it does not build 3D near-shading scenes from an obstruction survey. It takes a system description rather than a drawing of a specific building. Layout work needs a design platform.
Can SAM produce permit drawings or a customer proposal? No to both. There is no single-line diagram output, no DWG export, and no branded customer-facing proposal. Those deliverables sit entirely outside what SAM set out to do, which is why teams standardising on SAM end up producing them by hand.
Is SAM hard to learn? It has a steep learning curve and it is aimed at analysts rather than installers. The vocabulary assumes modelling familiarity. If you have the background, the transparency pays you back. If you do not, expect structured time rather than an afternoon.
Does SurgePV replace SAM? No, and it does not try to. They answer different questions. SAM handles techno-economic analysis and sensitivity work. SurgePV handles the design and delivery workflow: 8,760-hour simulation with module-level shading, single-line diagrams, DWG export, and white-label proposals in one licence.
Should I use SAM and a design platform together? For most EPCs doing feasibility work, yes. Use SAM early to decide whether a project or a technology mix is worth pursuing. Use the design platform once the answer is yes. For hybrid system studies, the HOMER Pro vs PVsyst comparison covers a similar split of duties.
Related: the bankability question in PVsyst vs SAM for bankable yield, the wider field in PVsyst alternatives, the cost picture in solar design software pricing, and hybrid modelling in HOMER Pro vs PVsyst.
