SAM Review: Industry-Standard Energy Simulation Software (2026)

TL;DR Summary

SAM (System Advisor Model) is a free, open-source solar financial modeling tool developed by the National Renewable Energy Laboratory (NREL) and the U.S. Department of Energy. Used by 50,000+ professionals in 180+ countries, SAM excels at detailed financial analysis (LCOE, PPA modeling, tax equity, P50/P75/P90 scenarios), making it the default choice for utility-scale developers, researchers, and policy analysts.

However, SAM is not a design platform. It lacks 3D modeling, panel layout tools, electrical engineering features (SLD generation, wire sizing), and customer-facing proposals. Commercial EPCs report steep learning curves (4-12 weeks) and time-intensive modeling (2-5 days per project). For teams needing integrated design, electrical documentation, and sales workflows, platforms like SurgePV deliver what SAM cannot.

Bottom Line: SAM is unbeatable for free financial depth. But if you need design tools, electrical engineering, and operational usability, you'll need commercial software.

What Is SAM (System Advisor Model)?

SAM is a desktop-based techno-economic modeling tool that simulates the performance and financial viability of renewable energy systems. Think of it as a financial analysis engine—not a design platform—focused on answering the question: "Is this project financially viable, and under what conditions?"

NREL and Department of Energy Background

SAM is developed and maintained by the National Renewable Energy Laboratory (NREL), a U.S. Department of Energy (DOE) national laboratory founded in 1977. With 3,000+ employees and a $464 million annual budget, NREL is the country's primary renewable energy research institution.

SAM development began in 2005 for internal DOE use. The first public release came in August 2007 as the "Solar Advisor Model" (version 1.0). In 2010, NREL expanded the tool to include wind, CSP, geothermal, and biomass technologies, renaming it the "System Advisor Model" to reflect this broader scope. In 2017, SAM became fully open-source under the BSD-3 license, with source code publicly available on GitHub.

Current version: SAM 2025.4.16 Revision 1, SSC 303

License: BSD-3-Clause (open source)

Development partner: Sandia National Laboratories

Downloads: 35,000+ since 2007

Registered users: 50,000+ globally

Geographic reach: 180+ countries

Core Capabilities

SAM is a simulation and financial modeling tool, not a design platform. Here's what it does:

• Performance modeling: 8760-hour energy simulations for solar PV, wind, CSP, geothermal, biomass, and hybrid systems
• Financial analysis: LCOE, NPV, IRR, payback period, PPA pricing, tax equity structures
• Uncertainty analysis: P50/P75/P90 scenarios using Monte Carlo sensitivity analysis
• Multi-technology support: Model solar, wind, storage, CSP, geothermal, biomass, and combinations
• Data integration: Access to NREL's National Solar Radiation Database (NSRDB), OpenEI utility rates, module/inverter libraries

What SAM Is NOT

SAM does not include:

• 3D roof or site modeling
• Panel layout or placement tools
• Single Line Diagram (SLD) generation
• Wire sizing or electrical engineering
• Customer proposals or sales outputs
• CRM integration or sales workflows
• Cloud-based multi-user collaboration
• Off-grid system modeling (grid-connected only)

This distinction is critical: SAM analyzes systems financially, but you must design them elsewhere.

SAM Features: What the Software Can Do

Performance Modeling

SAM's performance engine runs detailed simulations based on location-specific weather data, system configuration, and loss assumptions.

What it includes:

• 8760-hour simulation: Hour-by-hour energy modeling for an entire year
• Multiple PV technologies: Fixed-tilt, single-axis trackers, dual-axis trackers, concentrated PV
• Shading analysis: Import shading profiles from external tools (PVsyst, Helioscope)
• Loss modeling: Temperature degradation, soiling, snow, wiring, inverter clipping, module mismatch, aging

Feature: You can model complex systems with multiple array orientations, tracker configurations, and string layouts.

Advantage: SAM's hour-by-hour approach captures seasonal variations, edge-case losses, and time-of-use utility rate impacts.

Benefit: You get detailed production profiles for financial modeling—not just annual kWh estimates.

However, SAM assumes you've already determined system layout and configuration. It won't help you design panel placement, calculate roof area utilization, or optimize array spacing. You'll need solar design software first, then import parameters into SAM.

Financial Modeling (SAM's Strength)

This is where SAM shines. It offers the most comprehensive financial analysis of any free solar tool.

Financial metrics SAM calculates:

• LCOE (Levelized Cost of Energy): The "per-kWh cost" accounting for all capital, operating, and financing expenses over system lifetime
• NPV (Net Present Value): Present value of all future cash flows
• IRR (Internal Rate of Return): Rate of return on investment
• Payback period: Time to recover initial investment
• PPA pricing: Power Purchase Agreement rate modeling
• Tax equity modeling: ITC (Investment Tax Credit), PTC (Production Tax Credit), depreciation (MACRS)
• Debt/equity structures: Model different financing splits and terms

P50/P75/P90 Analysis: SAM runs Monte Carlo simulations to model uncertainty:

• P50: Median scenario (50% chance production is higher, 50% lower)
• P75: Conservative scenario (75% chance production is higher)
• P90: Worst-case scenario (90% chance production is higher)

This level of detail is critical for securing financing. Lenders and investors often require P75 or P90 estimates to assess downside risk. Aurora Solar, by comparison, provides only P50 estimates, making SAM essential for bankable financial projections.

Tax incentive updates: NREL actively maintains SAM to reflect current U.S. tax policy. The 2025 version includes Inflation Reduction Act (IRA) updates, production-based incentives, and domestic content bonuses.

Utility rate modeling: SAM integrates with OpenEI's database of 3,000+ U.S. utility rates, including complex time-of-use (TOU) structures, demand charges, and net metering rules. You can model customer savings under different rate schedules—critical for commercial solar installations.

Multi-Technology Support

Unlike design platforms focused solely on PV, SAM models:

• Solar PV: All technologies (monocrystalline, polycrystalline, thin-film, bifacial)
• Wind power: Onshore and offshore turbines
• CSP (Concentrated Solar Power): Parabolic trough, power tower, linear Fresnel
• Geothermal: Binary, flash steam
• Biomass: Direct combustion, gasification
• Battery storage: Lithium-ion, lead-acid, flow batteries
• Hybrid systems: Solar + storage, solar + wind + storage, etc.

This makes SAM the tool of choice for multi-technology feasibility studies, hybrid project analysis, and research comparing different renewable energy pathways.

Data Integration

SAM provides access to high-quality datasets:

• NREL NSRDB (National Solar Radiation Database): TMY3 (Typical Meteorological Year) weather data for thousands of global locations, updated regularly
• Module library: Specifications for 70,000+ solar modules
• Inverter library: Comprehensive database of residential, commercial, and utility-scale inverters
• OpenEI utility rates: 3,000+ U.S. utility rate structures

You can also import custom weather files (TMY2, EPW, CSV formats) for specific locations not in NREL's database.

SAM Pricing: Completely Free

Cost: $0—no subscription, no license fees, no feature limitations.

SAM is funded by the U.S. Department of Energy and developed by NREL as a public good. There is no commercial revenue model. This removes the single biggest barrier to adoption: cost.

What's included at no charge:

• Full software (Windows, macOS, Linux)
• All features (no tiered plans or feature gating)
• Community support forums
• Documentation and video tutorials
• Bi-weekly user roundtables (live Q&A with NREL developers)
• Regular updates and bug fixes

Open source: Since 2017, SAM's source code is available on GitHub under the BSD-3 license. Developers can customize, extend, or integrate SAM's calculation engine into their own software.

The Catch: No Official Support SLA

Because SAM is free government software, there's no guaranteed support. NREL provides:

• Community forums (active, but response time varies)
• Official documentation (comprehensive but sometimes outdated)
• GitHub issues (for bug reports and feature requests)

However, if your business is blocked by a SAM bug or you need urgent help, there's no SLA. You're relying on community volunteers or waiting for NREL's development roadmap.

Comparison: SurgePV costs $1,499/user/year (For 3 Users plan) with professional support (3-minute average response time). For commercial operations where downtime costs money, paid support can be worth the investment.

SAM Limitations: What the Software Cannot Do

SAM is powerful—but only within its scope. Here are the gaps commercial EPCs consistently report.

No Site Design or Visual Modeling

SAM has zero design capabilities. You cannot:

• Create 3D roof models
• Place panels visually
• Optimize array layout
• Import Google Maps or aerial imagery
• Calculate usable roof area
• Design ground-mount or carport layouts

Impact: You'll need separate solar design software (Aurora, SurgePV, PVCase, SketchUp) to determine system configuration before importing parameters into SAM.

Workflow implication: Design in Tool A (30-60 minutes) Transfer data manually to SAM (15-30 minutes) Run simulation. This adds time and introduces potential data entry errors.

No Electrical Engineering

SAM does not generate electrical documentation. It lacks:

• Single Line Diagram (SLD) generation
• Wire sizing calculations
• Voltage drop analysis
• Conduit routing
• Breaker sizing
• Protection device specifications

Impact: For commercial solar projects, you'll need AutoCAD, SurgePV's automated SLD features, or PVCase to produce permit-ready electrical drawings. This typically adds 2-3 hours per commercial project.

SAM assumes you've already handled electrical design. It focuses purely on performance and financial outputs.

No Sales or Proposal Features

SAM produces technical reports—not customer-facing proposals. It lacks:

• Branded proposal templates
• Interactive web-based outputs
• Customer ROI visualizations
• Financing comparison tools
• CRM integration (Salesforce, HubSpot)

Impact: Solar installers and sales teams can't use SAM outputs directly with customers. You'll need proposal software (Aurora, SurgePV, OpenSolar) to translate SAM's technical data into something a building owner or CFO can understand.

SAM is built for engineers and analysts—not sales workflows.

Desktop-Only, No Cloud

SAM runs on your local machine (Windows, macOS, Linux). There's no cloud version, which means:

• No real-time multi-user collaboration
• No access from mobile devices or tablets
• Version control challenges (manual file sharing)
• No centralized project library for teams

Impact: Teams working remotely or across multiple offices face friction. One person builds the SAM model, then emails the file to colleagues. No simultaneous editing or cloud backups.

Note: SAM does offer an SDK (Software Development Kit) for developers to integrate SAM's calculation engine into web apps, but this requires programming expertise.

Steep Learning Curve

SAM is powerful, but it's not intuitive. Users report:

• 4-12 weeks to basic proficiency: Understanding financial structures, input parameters, and result interpretation
• 6-12 months to expert level: Mastering uncertainty analysis, custom scripting, advanced configurations

NREL's forums are filled with questions like "What's the difference between 'Pre-tax IRR' and 'After-tax IRR (nominal)'?" or "How do I model a leveraged flip with tax equity?"

Comparison: Commercial tools like Aurora and SurgePV are designed for faster onboarding (2-3 weeks typical). SAM's depth comes at the cost of simplicity.

Impact: For high-volume commercial installers doing 20-50 projects per month, the time investment to train staff may not be justified unless you specifically need SAM's financial depth.

Time-Intensive Modeling

Building a complete SAM model is not fast. Users report:

• 2-5 days for a comprehensive utility-scale project model (performance + financial + sensitivity analysis)
• 4-8 hours for a commercial C&I project (if you know SAM well)

Compare this to commercial design platforms:

• SurgePV: 30-45 minutes for complete commercial design + electrical + proposal
• Aurora: 20-30 minutes for residential design + proposal

Why so slow? SAM requires manual input of hundreds of parameters: system configuration, financial assumptions, utility rates, degradation rates, O&M costs, tax structures, debt terms, and more. There's no "quick mode" for fast feasibility checks.

Use case fit: SAM is ideal for deep dives on large projects where you're validating financial viability over 25+ years. It's not practical for high-volume operations needing quick turnaround.

No Off-Grid Systems

SAM is explicitly designed for grid-connected systems only. Per NREL forum discussions, SAM cannot model:

• Standalone off-grid systems
• Microgrids (without grid connection)
• Battery-only off-grid storage

Source: NREL SAM Forum - Off-Grid System Thread

Impact: If you're designing remote power systems, cabins, telecom sites, or island microgrids, SAM won't work. Consider HOMER Energy, SAMA, or hybrid inverter manufacturer tools instead.

UI/UX Challenges

SAM's interface is functional but dated. Users report:

• Features buried in nested menus
• Inconsistent layout across Windows/Mac/Linux (release notes acknowledge Mac UI issues)
• No drag-and-drop workflows
• Spreadsheet-style data entry (not visual)

This isn't necessarily a dealbreaker for analysts comfortable with technical software, but it's a friction point for teams used to modern cloud apps.

Who Should Use SAM (System Advisor Model)?

Ideal SAM Users

SAM is best for professionals who need financial depth and are willing to invest time learning the tool.

1. Utility-scale solar developers (1MW-1GW+)

You're building large projects where financial modeling accuracy directly impacts securing financing. SAM's P75/P90 analysis, tax equity structures, and LCOE calculations are essential. The 2-5 day time investment per project is acceptable because each project is worth millions.

2. Academic researchers and universities

SAM is the industry standard for renewable energy research. It's peer-reviewed, open-source, and cited in thousands of academic papers. If you're publishing research on solar economics, policy impacts, or technology comparisons, SAM provides credibility and reproducibility.

3. Policy analysts and government agencies

You need to model "what-if" scenarios for incentive programs, renewable energy targets, or regulatory changes. SAM's flexibility and NREL credibility make it ideal for policy work.

4. Solar consultants doing feasibility studies

Your clients pay for detailed financial analysis and independent validation. SAM's NREL pedigree adds authority to your reports, and the free license improves your margins.

5. Project developers validating financial projections

You've already designed the system in another tool, but you want independent confirmation of financial performance. SAM acts as a "second opinion" to validate assumptions.

SAM Is NOT Ideal For

1. Commercial installers needing design tools

If you need to create 3D site models, place panels, and optimize layouts, SAM offers nothing. You'll spend your time in design software anyway—and SAM won't integrate directly.

2. Sales teams needing customer proposals

SAM produces technical output (charts, tables, financial metrics) that confuses customers. You need proposal software that translates data into "Your savings will be $X per year" with visual designs.

3. EPCs needing electrical engineering (SLD, wire sizing)

Without SLD generation or wire sizing, you're forced to use AutoCAD or SurgePV separately. This fragments your workflow and adds 2-3 hours per commercial project.

4. Teams needing cloud collaboration

If your engineers are distributed across offices or working remotely, SAM's desktop-only limitation creates version control headaches and file-sharing friction.

5. High-volume operations (20+ projects/month)

If you're churning out dozens of projects monthly, SAM's 2-5 day modeling time per project doesn't scale. You need faster tools optimized for operational speed.

SAM Pros and Cons Summary

SAM Pros

1. Completely Free

Zero cost removes the barrier to entry. No subscription, no per-project fees, no feature gates. Government-funded as a public good.

2. NREL Credibility

Developed by the U.S. Department of Energy's premier renewable energy lab. Lenders, investors, and utilities trust SAM outputs because of NREL's 40+ years of research credibility.

3. Financial Modeling Depth

Most comprehensive LCOE, PPA, tax equity, and debt/equity modeling available in any tool—free or paid. P50/P75/P90 uncertainty analysis is critical for bankable projects.

4. Multi-Technology Support

Model solar, wind, CSP, geothermal, biomass, storage, and hybrid systems in one platform. No other tool matches this breadth for free.

5. Open Source

Full source code on GitHub (BSD-3 license). Customize, extend, or integrate SAM's engine into your own software. Academic transparency for methodology.

6. Regular Updates

NREL actively maintains SAM with the latest tax incentives (IRA), weather data, and module/inverter libraries. Updates are free and frequent.

7. Academic Standard

Default tool for renewable energy research worldwide. Thousands of peer-reviewed papers cite SAM. If you're publishing, SAM provides credibility.

SAM Cons

1. Not a Design Tool

Zero design capabilities. No 3D modeling, panel layout, or visual site planning. You'll need separate design software before using SAM.

Impact: Fragmented workflow—design in Tool A, analyze in SAM, switch back to Tool A for revisions.

2. No Electrical Engineering

No SLD generation, wire sizing, or voltage drop calculations. Commercial projects require AutoCAD or SurgePV for electrical documentation.

Impact: Add 2-3 hours per commercial project for manual electrical work.

3. Steep Learning Curve

4-12 weeks to basic proficiency. Complex financial structures, hundreds of input parameters, and industry-specific terminology create barriers.

Impact: Significant training investment required. Not suitable for occasional users or sales teams.

4. Time-Intensive Modeling

2-5 days per comprehensive project model. No "quick mode" for fast feasibility checks.

Impact: Not practical for high-volume operations. Best for deep dives on large, complex projects.

5. Desktop-Only (No Cloud)

No real-time collaboration, no mobile access, manual version control.

Impact: Teams face friction sharing files, tracking changes, and working remotely.

6. No Sales Features

Technical outputs only—no customer proposals, CRM integration, or sales workflows.

Impact: Cannot streamline customer-facing processes. Need separate proposal software.

7. No Off-Grid Support

Grid-connected systems only. Cannot model standalone off-grid or microgrids.

Impact: Not suitable for remote power, island systems, or telecom applications.

SAM vs SurgePV: Which Should You Choose?

SAM and SurgePV are not direct competitors—they serve different purposes and markets. Here's how they compare.

Key Positioning

SAM: Financial analysis tool for utility-scale developers, researchers, and analysts. Free, deep financial modeling, but no design or electrical features.

SurgePV: End-to-end design platform for commercial EPCs and installers. Integrated design, electrical engineering, and proposals—but requires subscription.

Feature Comparison

When to Choose SAM

Choose SAM if you:

• Need deep financial analysis for utility-scale projects (1MW+)
• Require P75/P90 bankability metrics for lenders
• Are conducting academic research or policy analysis
• Have zero software budget
• Need NREL credibility for investor presentations
• Are modeling multi-technology projects (solar + wind + storage)
• Want to customize source code for specific use cases

When to Choose SurgePV

Choose SurgePV if you:

• Need complete commercial design workflow (10kW-10MW range)
• Require electrical engineering (SLD generation, wire sizing)
• Want integrated proposals for customer presentations
• Need cloud-based team collaboration
• Prioritize fast turnaround (hours vs. days)
• Design carport solar structures (SurgePV is the only platform with native support)
• Want professional support with guaranteed response times

Using Both (Complementary Workflow)

For large commercial or small utility projects (500kW-5MW), some teams use both:

Step 1: Design in SurgePV (3D layout, electrical, shading) - 30-45 minutes

Step 2: Export parameters to SAM for financial validation (LCOE, P75/P90) - 4-8 hours

Step 3: Use SurgePV proposal for customer presentation

This workflow gives you operational efficiency (SurgePV) plus financial credibility (SAM) when lenders specifically request NREL-validated projections.

Bottom Line: Design in SurgePV, validate financially in SAM (optional, for 1MW+ projects requiring bankability). Use SurgePV for daily workflow.

SAM Alternatives: Other Solar Modeling Tools

If SAM doesn't fit your needs, consider these alternatives.

PVsyst (Bankable Simulation)

What it is: Desktop-based PV simulation software, industry standard for bankable energy yield reports.

Strengths:

• Deepest PV-specific simulation detail (shadow analysis, bifacial modeling, inverter behavior)
• Universally accepted by lenders and investors for bankability
• Extensive loss modeling and validation tools

Limitations:

• Not a design platform (simulation only)
• Desktop-only (no cloud)
• Steep learning curve (similar to SAM)
• Paid software (~$4,200 for commercial license)

Best for: Utility-scale validation, financing documentation, independent engineer (IE) reports

When to choose: You need lender-accepted bankability and don't mind paying for PVsyst's specific credibility. PVsyst focuses on PV simulation only (no wind, geothermal, etc.).

PVWatts (Simple Free Calculator)

What it is: Web-based calculator from NREL, simplified version of SAM's performance engine.

Strengths:

• Free, fast (30 seconds for estimate)
• No learning curve—simple form-based inputs
• Web-based (no installation)

Limitations:

• No financial modeling
• No detailed loss configuration
• No design tools

Best for: Quick feasibility checks, ballpark estimates, homeowners researching solar

When to choose: You need a rough energy estimate in under a minute. Not suitable for commercial projects or financial analysis.

SurgePV (Complete Design Platform)

What it is: Cloud-based platform combining design, electrical engineering, shading analysis, and proposals.

Strengths:

• End-to-end workflow (design + electrical + proposals in one platform)
• Automated SLD generation and wire sizing (no AutoCAD needed)
• Cloud-based multi-user collaboration
• 2-3 week onboarding (faster than SAM or PVsyst)
• Native carport design (only platform)
• Commercial-focused features

Limitations:

• Subscription cost ($1,499/user/year for For 3 Users plan)
• Financial modeling less comprehensive than SAM (basic LCOE, ROI)

Best for: Commercial EPCs, installers, teams needing electrical engineering, complete workflow from design to proposal

When to choose: You want design, electrical, and sales in one platform. You need operational speed (30-45 minutes per project vs. SAM's days). See SurgePV pricing.

Aurora Solar (Residential Focus)

What it is: Cloud-based design and proposal platform, market leader for residential solar.

Strengths:

• Best-in-class AI roof modeling
• Beautiful customer proposals
• Strong Salesforce/HubSpot integration
• Large user base and community

Limitations:

• No electrical engineering (SLD, wire sizing)
• No carport design
• No tracker support
• Only P50 estimates (no P75/P90)
• Tiered pricing (contact sales)

Best for: Residential installers, sales-focused teams, companies prioritizing proposal aesthetics

When to choose: You're residential-focused and don't need electrical depth. For commercial EPCs, see Aurora alternatives.

SAM vs SurgePV: Feature Comparison

How SAM compares to SurgePV across the features commercial EPCs need most.

Final Verdict: Should You Use SAM (System Advisor Model)?

SAM Summary

Strengths: Free, comprehensive financial modeling (LCOE, PPA, tax equity, P75/P90), NREL credibility, multi-technology support, open-source transparency, regular updates

Ideal for: Utility-scale solar developers (1MW+), academic researchers, policy analysts, consultants doing feasibility studies, project developers validating financial projections

Limitations: Not a design tool, no electrical engineering, no sales features, steep learning curve (4-12 weeks), time-intensive modeling (2-5 days per project), desktop-only (no cloud), no off-grid support

Recommendation

For utility-scale financial analysis: SAM is excellent and free. If you're building large projects where financial modeling accuracy directly impacts securing financing, SAM's depth and NREL credibility are unmatched. The 4-12 week learning curve and 2-5 day modeling time are acceptable when each project is worth millions.

For commercial installer workflow: SAM likely isn't the right fit. You need design tools, electrical engineering (SLD generation, wire sizing), and fast turnaround for customer proposals. Platforms like SurgePV deliver integrated workflows (design + electrical + proposals in 30-45 minutes) that SAM cannot.

For many professionals: SAM and commercial design software are complementary, not either/or. Design in SurgePV or Aurora for operational efficiency, then optionally use SAM for financial validation when lenders specifically request P75/P90 analysis or NREL-backed projections.

Bottom Line

"SAM is the best free financial modeling tool for utility-scale solar, renewable energy research, and policy analysis. But for commercial EPCs needing design, electrical engineering, and customer proposals in one integrated workflow, SurgePV delivers what SAM cannot."

SAM excels at what it's built for: deep financial analysis. It's not trying to be a design platform or sales tool—and that's okay. Use it for its strengths, and fill the gaps with purpose-built commercial software when needed.

Ready for Complete Solar Design Workflow?

SAM excels at financial analysis, but commercial EPCs need more: visual design, automated electrical documentation, customer proposals, and cloud collaboration.

SurgePV combines everything in one platform:

• 3D design with AI roof detection
• Automated SLD generation (5-10 minutes vs. 2-3 hours in AutoCAD)
• Wire sizing and voltage drop calculations (no separate CAD tools needed)
• Professional customer proposals (interactive web links or branded PDFs)
• Cloud-based team collaboration (multi-user, real-time)
• Commercial structures (carports, trackers, East-West racking)
• $1,499/user/year (For 3 Users plan) with 3-minute average support response

Book a 15-minute demo to see how SurgePV handles design, electrical engineering, and proposals without tool-switching.

Book Demo | Compare Pricing | See All Features

Related Reading:

• Best Solar Design Software for Commercial Projects
• Aurora Solar Review: Pros, Cons & Alternatives
• PVsyst Review: Bankable Simulation for Solar Projects
• Best Solar Proposal Software
• Commercial Solar Design Solutions
• Helioscope Review: Cloud-Based Solar Design
• OpenSolar Review: Affordable Solar Software
• PVCase Review: CAD-Based Solar Design