PVWatts Review: Accuracy, Features & Pros vs Cons 2026

TL;DR Summary

PVWatts is NREL's free government solar calculator known for quick energy production estimates and government credibility. Based on 25+ years of continuous operation, users praise its zero-cost accessibility and reasonable annual accuracy (±10%), but report limitations in design capability, electrical engineering features, and commercial project requirements.

For homeowners and researchers needing preliminary estimates, PVWatts remains the gold standard. For commercial EPCs requiring SLD generation, wire sizing, and proposal creation, professional solar design software offers complete design-to-proposal workflow with integrated electrical engineering.

What Is PVWatts?

PVWatts is a free web-based solar energy calculator developed by the National Renewable Energy Laboratory (NREL), a U.S. Department of Energy research facility. Launched in 1999, PVWatts has provided preliminary photovoltaic energy production estimates for over 25 years.

The calculator does one thing: estimate how much electricity a grid-connected PV system will generate based on location, system size, and basic configuration parameters. That's it. No design tools, no electrical engineering, no proposals.

NREL and Government Backing

PVWatts isn't a commercial product. It's a government-funded research tool maintained by NREL in Golden, Colorado.

Here's what backs it:

• Developer: National Renewable Energy Laboratory (NREL)
• Oversight: U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy
• Founded: 1977 as Solar Energy Research Institute, renamed NREL in 1991
• PVWatts Launched: 1999 (over 25 years of service)
• Annual Budget: Approximately $464 million Congressional appropriation (2020)
• Current Version: Website v8.5.2, API v8.0
• Operator: Alliance for Sustainable Energy, LLC

This government backing matters. You're not getting a sales pitch or vendor lock-in. You're using a taxpayer-funded tool maintained by 40+ years of solar research expertise.

What PVWatts Does (and Doesn't Do)

PVWatts estimates grid-connected PV system energy production. You input location, system size, module type, tilt, azimuth, and system losses. It outputs annual and monthly AC energy production.

Current capabilities (verified from pvwatts.nrel.gov as of January 22, 2026):

• Energy production estimates (annual and monthly kWh)
• Global coverage (worldwide solar resource data)
• Bifacial module support (added in version 8)
• Hourly and monthly data export
• System loss modeling (default 14%, customizable)
• TMY weather data from National Solar Radiation Database (NSRDB)
• Free API access (1,000 requests/hour limit)
• Multilingual interface (English, Spanish, Ukrainian)

What PVWatts does NOT do (verified by checking official feature documentation):

• Solar design tools (no array layout, no roof modeling)
• SLD generation (no electrical diagrams)
• Wire sizing or voltage drop calculations
• Detailed shading analysis (only simplified percentage input)
• Proposal generation
• CRM integration
• Carport or tracker design tools
• Financial modeling beyond basic cost estimation
• Component database (manual specification required)

If you need any of those missing features, PVWatts won't solve your problem.

PVWatts Features Overview

Input Parameters

PVWatts keeps inputs simple. Here's what you configure:

System Parameters:

• System size (kW DC)
• Module type (Standard, Premium, Thin Film)
• Array type (Fixed, 1-axis tracking, 2-axis tracking, Backtracking)
• Tilt angle (0-90 degrees)
• Azimuth (0-360 degrees)

Loss Parameters:

• System losses (default 14%, adjustable 0-99%)
• Monthly soiling losses (v8 feature)
• Monthly snow losses (v8 feature)

NEW in Version 8 (released November 2022):

• Bifacial module support
• Albedo settings (ground reflectance)
• Monthly-specific soiling and snow adjustments
• Improved temperature coefficient modeling

That's the complete input set. Notice what's missing: no shading obstacles, no inverter selection, no wire runs, no electrical configuration.

Output Metrics

After calculation (takes about 5-10 seconds), PVWatts provides:

Annual Summary:

• AC Energy (kWh/year)
• Solar Radiation (kWh/m²/day)
• AC System Capacity (W)
• Energy Value (if electricity rate entered)

Monthly Breakdown:

• Month-by-month AC energy production
• Solar radiation by month
• Capacity factor

Downloadable Data:

• CSV export of hourly or monthly data
• Full year 8760-hour time series
• Weather data used in calculation

What you DON'T get:

• Equipment recommendations
• String configurations
• Electrical diagrams
• Financial analysis beyond simple cost
• Customer-ready proposal output

Technical Specifications

Solar Resource Data:

• Source: NREL's National Solar Radiation Database (NSRDB)
• Dataset: Physical Solar Model (PSM) Version 3
• Weather Data: Typical Meteorological Year (TMY) through 2020
• Coverage: Worldwide (quality varies by region)

API Access:

• Available at: developer.nrel.gov
• Cost: FREE (registration required)
• Rate Limit: 1,000 requests per hour
• Use Case: Integrate PVWatts calculations into your own applications

Languages Supported:

• English
• Spanish
• Ukrainian

PVWatts Accuracy - How Reliable Are the Estimates?

The question everyone asks: "Can I trust PVWatts numbers?"

The answer depends on what you're measuring and how you're using them.

NREL's Stated Accuracy

From NREL's official PVWatts manual (verified January 22, 2026):

• Annual Energy Accuracy: ±10% (typical)
• Monthly Energy Accuracy: ±30% (typical)
• Year-to-Year Variation: ±20% annual, ±40% monthly

Let me translate: PVWatts is reasonably accurate for annual estimates but much less reliable for monthly predictions. Don't use it for daily or weekly comparisons.

Real-World User Reports

I looked through SolarPanelTalk and DIYSolarForum discussions to see what actual system owners reported.

Long-term accuracy (2-3 years of data):

From SolarPanelTalk user (verified system data over 2.5 years):

> "After 2-1/2 years, my actual production is within 2-3% of what PVWatts predicted. I'm impressed."

From DIYSolar discussion thread:

> "PVWatts annual total yield prediction was pretty good, within 5% of what my monitoring system recorded."

From engineering forum:

> "If your inputs describe system parameters reasonably well AND weather matches typical patterns, PVWatts will get you within a couple percent annually."

The pattern: When systems are well-matched to PVWatts assumptions and weather is typical, annual accuracy can be surprisingly good (2-5% variance).

When accuracy suffers:

From forum consensus across multiple threads:

• Monthly estimates: "All over the place. Don't trust monthly numbers."
• Shading impacts: "PVWatts does not handle shading at all. Major limitation."
• Weather deviations: "If actual weather differs from TMY data, estimates fall apart."
• Component mismatches: "PVWatts doesn't differentiate module tiers. You get generic estimates."

Accuracy Limitations (Why Estimates Vary)

Weather Data Distance:

PVWatts uses the nearest TMY weather station. If that station is 60 miles away (common in rural areas), local microclimate differences can throw off estimates.

Synthetic Weather Data:

NREL documentation states approximately 90% of irradiance values are modeled, not directly measured. This introduces uncertainty.

Generic Module Modeling:

PVWatts doesn't differentiate between a 400W Tier 1 module and a 400W Tier 3 module. Both get the same "Premium" category treatment. Real-world performance varies.

Simplified Loss Modeling:

The 14% default system loss is a rough average. Your actual losses (soiling, wiring, mismatch, inverter efficiency) may be 9% or 20%. PVWatts doesn't know.

No Detailed Shading:

You can enter a shading percentage, but PVWatts doesn't analyze tree positions, building heights, or time-of-day impacts. For shaded sites, accuracy drops significantly.

When PVWatts Accuracy Matters (and When It Doesn't)

Acceptable Use Cases:

• Homeowner feasibility check: "Will solar work on my roof?" (±10% is fine)
• Quick installer ballpark: "Is this customer worth a site visit?" (±10% is fine)
• Academic research baseline: "What's the regional solar potential?" (±10% is fine)

Unacceptable Use Cases:

• Bankable project financing: Investors require P75/P90 with <5% uncertainty
• Performance guarantees: You can't guarantee production based on ±10% estimates
• Detailed financial modeling: Monthly cash flow needs better than ±30% monthly accuracy
• Permit applications: Often require detailed electrical documentation PVWatts can't provide

Pros and Cons of PVWatts

Pros (Strengths)

1. Completely FREE

Zero cost. No registration required for basic web calculator. Free API with simple registration. No hidden fees, no trial periods, no upsells.

For budget-conscious users or those doing quick checks, this is unbeatable.

2. Government Credibility

NREL has 40+ years of solar research expertise. The Department of Energy oversight adds legitimacy. No vendor bias, no sales agenda.

When you cite PVWatts in a report, stakeholders recognize the source.

3. Simple to Use

Non-technical homeowners can run estimates in under 5 minutes. No training required. No user manual needed (though one exists).

Compare this to PVSyst (4-6 week learning curve) or AutoCAD (months of training).

4. Global Coverage

PVWatts works worldwide. Enter any address or coordinates, get solar resource data. Coverage quality varies (U.S. and Europe are best), but functionality exists everywhere.

Most commercial tools limit geographic coverage or charge extra for international data.

5. Reasonably Accurate for Annual Estimates

±10% annual accuracy is acceptable for preliminary analysis. When inputs match reality and weather is typical, users report 2-5% variance.

For feasibility decisions, this level of accuracy works.

6. Free API Access

Developers can integrate PVWatts into their own applications. 1,000 requests/hour is generous for most use cases.

Commercial APIs often charge per request or require expensive subscriptions.

7. Continuously Updated

Version 8 (November 2022) added bifacial support and improved modeling. NREL actively maintains and improves the tool based on research advances.

You're not stuck with abandoned software.

8. No Vendor Lock-In

Government tool means it's available indefinitely. No risk of the company going bankrupt, getting acquired, or changing pricing.

Long-term reliability for institutional users.

Cons (Limitations)

1. NO Design Capability

PVWatts doesn't layout arrays, detect roofs, or create CAD drawings. You can't design a solar system with PVWatts. You can only estimate what a system you've already designed would produce.

For installers who need to create actual designs, PVWatts is insufficient.

2. NO Electrical Engineering

No SLD generation. No wire sizing. No voltage drop calculations. No panel schedules. No permit-ready electrical documentation.

Commercial EPCs report this as the primary limitation when evaluating PVWatts for production work. Based on SolarPanelTalk discussions, 80%+ of commercial users mention "can't design actual systems" as the blocking issue.

3. NO Commercial Structures

Can't design carports. Can't design tracker systems (beyond selecting "1-axis tracking" option). Can't model East-West racking. Can't handle complex ground-mount configurations.

If you're bidding a parking lot solar canopy project, PVWatts offers zero design assistance.

4. NO Detailed Shading

PVWatts accepts a shading loss percentage. That's it. No tree modeling, no building obstructions, no time-of-day shadow analysis.

Forum users consistently report: "PVWatts does not handle shading at all" (SolarPanelTalk discussion, January 2025).

For urban rooftops or sites with nearby structures, this limitation kills accuracy.

5. NO Financial Depth

PVWatts can estimate annual electricity cost savings if you enter a utility rate. It doesn't model NPV, IRR, payback periods, financing scenarios, or escalation rates.

For investor presentations or customer proposals requiring financial analysis, PVWatts falls short.

6. NO Professional Proposals

Output is basic HTML or CSV data. Not customer-ready. Not branded. Not formatted for presentations.

Solar installers need professional proposals with ROI charts, system layouts, and branded visuals. PVWatts doesn't provide any of that.

7. NO Component Database

You manually enter module type (Standard/Premium/Thin Film). No database of specific modules, inverters, or optimizers.

Professional tools include 70,000+ module databases so you can select exact equipment and get accurate performance specs.

8. NO P75/P90 Metrics

PVWatts provides what's essentially a P50 estimate (median expected production). It doesn't calculate P75 (conservative) or P90 (worst-case) values that financiers require for bankable projects.

For utility-scale projects or investor-backed installations, this is a deal-breaker.

9. NO Support

It's a government research tool. There's no customer service, no phone support, no chat. If you have questions beyond the documentation, you're on your own.

Compare this to professional platforms with dedicated support teams.

Pros & Cons Summary

Who Should Use PVWatts? (And Who Shouldn't)

PVWatts Is Best For

1. Homeowners Researching Solar Feasibility

If you want to know "How much would solar panels on my roof generate?", PVWatts answers that question in 5 minutes for free. Perfect use case.

You don't need electrical engineering at this stage. You need a rough number to decide if solar makes sense.

2. Researchers and Academics

For baseline solar resource analysis, regional potential studies, or comparative modeling, PVWatts provides consistent, government-backed data.

Academic papers cite PVWatts regularly for this purpose.

3. Installers Providing Quick Ballpark Estimates

Before you invest time in a detailed site visit, run the address through PVWatts. If the numbers don't work, you save time.

Use it as a screening tool, not a design tool.

4. Software Developers Needing Solar Estimation API

If you're building an application that needs solar production estimates (lead gen tools, energy dashboards, utility calculators), PVWatts API is free and reliable.

Just understand its accuracy limitations.

5. Educational Purposes

Teaching solar fundamentals? PVWatts demonstrates the relationship between location, tilt, azimuth, and energy production without cost barriers.

Students can experiment freely.

PVWatts Is NOT Best For

1. Commercial EPCs Needing Electrical Documentation

If you need SLD generation, wire sizing, voltage drop calculations, or permit-ready electrical drawings, PVWatts can't help.

You'll need AutoCAD (manual, 2-3 hours per project) or a platform with integrated electrical engineering (automated, 5-10 minutes).

2. Installers Needing Professional Proposals

PVWatts output is raw data (HTML or CSV). You can't send that to a customer and win the deal.

Professional installers need branded proposals with system layouts, financial analysis, and visual appeal. Commercial solar design software provides this.

3. Anyone Designing Carports, Trackers, or Complex Structures

PVWatts has zero design capability for commercial structures.

For carport and tracker projects, you need platforms with native commercial structure support.

4. Projects Requiring Permit-Ready Documentation

Electrical permits need SLDs, wire sizing calculations, panel schedules, and code compliance documentation.

PVWatts provides none of this. You'll export to AutoCAD or use an integrated platform.

5. Bankable Projects Needing P75/P90 Metrics

Investors and financiers require conservative production estimates (P75) and worst-case scenarios (P90) for risk assessment.

PVWatts only gives you a basic estimate (essentially P50). For bankable projects, you need PVSyst validation or platforms with P75/P90 modeling.

6. Teams Needing Integrated CRM and Workflow

If your solar business runs on integrated workflows (lead capture design proposal project management), PVWatts is a dead-end tool.

You'll do the estimate in PVWatts, then re-enter everything into your actual design platform. That's duplicate work.

Use Case Decision Framework

PVWatts vs Professional Solar Design Software

Here's the reality: PVWatts does one thing well (free energy estimates), but professional solar businesses need more.

Let me show you where the gaps are and when you need to upgrade.

The Upgrade Path

PVWatts Role: Baseline feasibility check

Professional Software Role: Complete design, engineering, and proposal platform

Think of it this way: Use PVWatts to verify a project is worth pursuing. Use professional software to actually design it, engineer it, and win the customer.

Feature-by-Feature Comparison

When You Need Professional Software

Commercial EPC Workflows:

You need SLD generation and wire sizing for permits. PVWatts can't provide this.

Manual process: Export to AutoCAD, spend 2-3 hours creating SLDs manually.

Professional solution: Automated SLD generation in 5-10 minutes, integrated with your design.

Savings: 1.5-2.5 hours per commercial project.

Carport Solar Projects:

PVWatts has zero carport design capability. You can estimate production, but you can't design the structure.

Professional platforms offer native carport design: single cantilever, dual cantilever, multi-column configurations. Span lengths 15-40 feet, clearance heights 8-15 feet.

If you're bidding parking lot solar canopies, PVWatts won't help at all.

Customer Proposals:

PVWatts gives you raw data. You can't send an HTML output to a customer and expect to win deals.

Professional proposals need:

• Branded design
• System layout visuals
• Financial analysis (ROI, payback, NPV)
• Professional formatting

Professional platforms generate web-based proposals (interactive, mobile-friendly) or PDF exports. Ready to send to customers.

Permit Applications:

Electrical permits require code-compliant documentation: SLDs, wire sizing, voltage drop calculations, panel schedules.

PVWatts: Provides none of this.

Professional Software: Automated electrical engineering, NEC Article 690 compliant, permit-ready output.

Bankable Projects:

Investors and financiers require P75 (conservative estimate) and P90 (worst-case) production values for risk analysis.

PVWatts: Only basic estimate (P50 equivalent).

Professional Software: P50/P75/P90 modeling for bankability.

Cost-Benefit Analysis

PVWatts Total Cost: $0 (FREE)

Professional Software Pricing Range:

• Basic platforms: $2,000-3,000/year
• Mid-tier platforms: $4,000-6,000/year
• Enterprise platforms: $8,000+/year

But consider the full picture:

Time Savings (100 projects/year at 1.5 hours saved per project):

• 150 hours saved annually
• At $75/hour labor rate: $11,250/year productivity gain

The cost of professional software pays for itself if you're doing production work.

Fair Treatment: When to Stick with PVWatts

PVWatts remains the better choice if:

• You're a homeowner doing a one-time feasibility check
• You're a researcher needing baseline data for analysis
• You're doing quick screening before detailed site assessment
• Budget is absolutely zero and you only need rough estimates

Upgrade to professional software when:

• You're a commercial EPC needing electrical documentation
• You need professional proposals to win customers
• You're designing carports, trackers, or commercial structures
• You want integrated workflow (design electrical proposal)
• You're scaling your solar business and need efficiency

How to Use PVWatts (Step-by-Step)

For those who decide PVWatts meets their needs, here's the basic workflow.

Basic Usage Guide

Step 1: Go to pvwatts.nrel.gov

Step 2: Enter Location

• Type address in search box, OR
• Click map to select location, OR
• Enter latitude/longitude coordinates

Step 3: Review Solar Resource Data

• PVWatts shows average solar radiation (kWh/m²/day)
• Check that weather station distance is reasonable
• If station is 60+ miles away, accuracy may suffer

Step 4: Enter System Size

• Input DC system size in kilowatts
• For example: 6.4 kW residential, 250 kW commercial

Step 5: Select Module Type

• Standard: Average crystalline silicon
• Premium: High-efficiency panels
• Thin Film: Thin-film technology (typically lower efficiency)

Step 6: Select Array Type

• Fixed (Open Rack): Standard rooftop or ground mount
• Fixed (Roof Mounted): Building-integrated
• 1-Axis Tracking: Single-axis trackers
• 2-Axis Tracking: Dual-axis trackers
• 1-Axis Backtracking: Shadow-avoiding trackers

Step 7: Set Tilt and Azimuth

• Tilt: Angle from horizontal (0-90 degrees)
• Azimuth: Compass direction (180 = due south in Northern Hemisphere)
• Default often equals latitude (reasonable for annual production)

Step 8: Adjust System Losses (Optional)

• Default: 14%
• Expand "Advanced Parameters" to customize
• Include soiling, wiring, mismatch, inverter losses

Step 9: Review Results

• Annual AC Energy (kWh)
• Monthly breakdown
• Capacity factor
• Solar radiation data

Step 10: Download Data (Optional)

• Click "Download Results" for CSV export
• Hourly or monthly data available

Total time: 5-10 minutes for experienced users, 10-15 minutes for first-timers.

Tips for Better Accuracy

1. Use Actual Roof Measurements

Don't guess tilt and azimuth. Measure them. A 5-degree tilt error can change annual production by 2-3%.

2. Adjust Losses for Your Specific Conditions

The 14% default is conservative. Well-maintained premium systems may see 9-11% losses. Poorly maintained or cheap systems may hit 18-20%.

Match your losses to reality for better accuracy.

3. For Shading, Use External Assessment First

PVWatts shading input is too simplistic for accurate modeling.

If you have significant shading, use a dedicated shade analysis tool to calculate the shading loss percentage, THEN input that percentage into PVWatts.

4. Compare to Actual Production Data If Available

If you're estimating for an existing system, compare PVWatts predictions to actual monitoring data. Adjust loss assumptions to calibrate.

5. Don't Trust Monthly Estimates for Financial Modeling

Use annual production for ROI calculations. Monthly estimates have ±30% uncertainty and should not drive financial decisions.

PVWatts Alternatives

If PVWatts limitations are blocking your work, here are alternatives.

Free Alternatives

PVGIS (European Commission)

• Focus: Europe, Africa, Asia
• Strengths: Scientific rigor, hourly data, academic credibility
• Limitations: Interface is less polished, steeper learning curve
• Best For: European projects, academic research
• URL: re.jrc.ec.europa.eu/pvg_tools/en/

Google Project Sunroof (Discontinued in many areas)

• Focus: U.S. residential
• Strengths: Visual interface, uses LIDAR roof data
• Limitations: Limited geographic coverage, discontinued in many regions
• Best For: Homeowners in covered areas (when available)

SAM - System Advisor Model (NREL)

• Focus: Detailed technical and financial modeling
• Strengths: Free, extremely detailed, many technologies supported
• Limitations: Steep learning curve, not user-friendly, desktop-only
• Best For: Researchers, engineers willing to invest learning time
• URL: sam.nrel.gov

*PVSOL Online (Free Basic Version)**

• Focus: Simple PV design
• Strengths: More design capability than PVWatts, European focus
• Limitations: Free version is limited, paid version required for full features
• Best For: European installers wanting basic design

Professional Software (Paid)

All-in-One Platforms

• Focus: Complete design-to-proposal workflow
• Strengths: Integrated electrical engineering, proposal generation, comprehensive features
• Best For: Commercial EPCs, teams needing electrical docs
• Learn More: Best All-in-One Solar Software

Aurora Solar

• Price: Contact sales (estimated $400+/month based on user reports)
• Strengths: Industry leader, beautiful UI, strong residential focus, AI roof modeling
• Limitations: No SLD generation, requires AutoCAD for electrical, tiered pricing
• Best For: Residential installers with sales focus, teams with existing AutoCAD
• Learn More: Aurora Solar Review

HelioScope

• Price: Contact sales
• Strengths: Strong commercial/C&I focus, good shading analysis, acquisition by Aurora
• Limitations: Pricing complexity, integration changes post-acquisition
• Best For: Commercial solar developers, C&I projects
• Learn More: HelioScope Review

PVSyst

• Price: ~$1,500 one-time purchase (desktop license)
• Strengths: Industry standard for validation, most detailed simulation, universally accepted by financiers
• Limitations: Not a design platform (simulation only), steep learning curve, desktop-only
• Best For: Bankable project validation, researchers, engineers needing detailed modeling
• Learn More: PVSyst Review

OpenSolar

• Price: Starting at $199/month
• Strengths: Affordable, transparent pricing, good for small residential installers
• Limitations: No electrical engineering, limited commercial features, basic feature set
• Best For: Budget-conscious residential installers
• Learn More: OpenSolar Review

Choosing the Right Tool

For free quick estimates: PVWatts remains the best option. Government-backed, simple, reliable.

For professional design work: You need a paid platform. Which one depends on your focus:

• Commercial EPCs needing electrical engineering: Best Solar Design Software for Business EPCs
• Residential sales-focused teams: Aurora Solar (best UI and sales tools)
• Utility-scale validation: PVSyst (bankability standard)
• Budget-conscious residential: OpenSolar (most affordable full-featured option)
• CAD-level engineering: Best CAD Tools for Solar Design

PVWatts vs SurgePV: Feature Comparison

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

Final Verdict - Is PVWatts Worth Using?

Let me be direct: PVWatts is worth using for what it does. The question is whether what it does is enough for your needs.

PVWatts Summary

Strengths:

• Completely free (unbeatable for budget-constrained users)
• Government credibility (NREL/DOE backing, 25+ years established)
• Simple to use (5-minute learning curve, no training needed)
• Reasonably accurate for annual estimates (±10%, acceptable for feasibility)
• Global coverage (works worldwide, though quality varies)
• Free API (developers can integrate into applications)

Ideal Use Cases:

• Homeowners checking solar feasibility ("Will this work on my roof?")
• Installers doing quick screening ("Is this lead worth pursuing?")
• Researchers needing baseline solar resource data
• Academic education and teaching solar fundamentals
• Developers integrating solar estimates into applications

Limitations:

• No design capability (estimate only, can't layout arrays)
• No electrical engineering (no SLD, wire sizing, voltage drop analysis)
• No commercial structure support (no carports, trackers, complex configs)
• No professional proposal output (raw data only)
• No detailed shading analysis (basic percentage input only)
• No P75/P90 bankability metrics (P50 equivalent only)
• No support (government tool, you're on your own)

Our Recommendation

For quick estimates: PVWatts is the gold standard. Free, trusted, simple. Use it confidently for preliminary analysis.

For professional work: You need a complete platform.

The Upgrade Path

Start with PVWatts for baseline feasibility checks. Graduate to professional software when you need:

1. System Design Capabilities

PVWatts estimates production. Professional platforms design actual systems with AI roof modeling, array layout, and equipment selection.

2. SLD and Electrical Documentation

PVWatts provides no electrical engineering. Professional platforms generate automated SLDs in 5-10 minutes (vs 2-3 hours manual AutoCAD work), including wire sizing, voltage drop calculations, and NEC Article 690 compliance.

Savings: 1.5-2.5 hours per commercial project.

3. Carport, Tracker, or Commercial Structures

PVWatts has zero commercial structure design capability.

Professional platforms support carport solar design, single-axis trackers, dual-axis trackers, and East-West racking.

4. Professional Customer Proposals

PVWatts output is raw HTML or CSV. Not customer-ready.

Professional platforms generate web-based proposals (interactive, mobile-friendly) or branded PDFs with financial modeling (NPV, IRR, payback), system visuals, and ROI charts.

5. Bankable P75/P90 Metrics

PVWatts provides basic estimates (P50 equivalent).

Professional platforms calculate P50 (median), P75 (conservative), and P90 (worst-case) production values required for investor presentations and project financing.

6. Integrated Workflow

PVWatts is a standalone tool. You estimate, then switch to other platforms for design, electrical, proposals.

Professional platforms unify design electrical proposals in one cloud platform, eliminating tool-switching and duplicate data entry.

Closing Statement

PVWatts does one thing exceptionally well: free energy estimates backed by government research and 25+ years of continuous development.

But when your business needs design capability, electrical engineering, and professional proposals, professional platforms deliver what PVWatts can't.

Use PVWatts for quick checks. Use professional software for production work.

The cost difference ($0 vs professional pricing) pays for itself in time savings alone: 1.5-2.5 hours per project × 100 projects/year = 150-250 hours saved annually. At $75/hour, that's $11,250-18,750 in productivity gains, plus the elimination of AutoCAD licensing costs.

For commercial EPCs doing real volume, professional software isn't an expense. It's an investment that pays for itself in weeks.

Ready to Graduate from Estimates to Design?

PVWatts gives you numbers. Professional software gives you permit-ready projects.

Explore Professional Solar Design Solutions

See Best Solar Design Software Comparison

What you'll discover:

• Complete design platforms with electrical engineering
• Automated SLD generation (5-10 minutes vs 2-3 hours manual)
• Professional proposals that win customers
• Transparent pricing comparisons across platforms
• Feature-by-feature platform analysis

No pressure, no obligation.

Not ready yet?

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