Rooftop PV yield and layout tools

National Laboratory of the Rockies (NLR, formerly NREL) · Desktop app (Windows, macOS, Linux) · Free; registration gives a free software key

Free, detailed simulation of a PV system's hourly production, including self-shading between rows and a 3D shade scene.

• A free desktop application for techno-economic analysis of energy technologies, covering photovoltaic systems from small residential rooftops to utility scale.
• Estimates self-shading between rows from the ground coverage ratio, the row width divided by the distance between the bottoms of neighbouring rows.
• A 3D Shade Calculator draws the array with nearby boxes, cylinders, trees and roofs, optionally over an aerial photograph, and turns the scene into hourly beam shade losses for a year.

Good to know

• Self-shading is modelled only for fixed and one-axis tracking subarrays laid out as parallel rows with the same number of modules in each.

Visit System Advisor Model (SAM)

OpenSolar · Design and sales platform for solar professionals · Free for solar professionals; premium imagery can be bought per project

Free automated rooftop layouts and production estimates for installers designing and quoting systems.

• Roof planes and obstructions are set on imagery or a photogrammetry-based digital surface model, and the arrays are placed automatically, with 3D renders.
• Production is calculated with an engine based on the System Advisor Model, with shading analysis that traces the sun through the day, month and year.
• Panels flash red when they are about to be placed inside a setback boundary; a sketch tool on 2D imagery covers sites with no 3D imagery.

Good to know

• Built for solar businesses to design, sell and manage projects; OpenSolar is funded by partners such as manufacturers, distributors and finance companies.

Visit OpenSolar

Google · Web API (Google Maps Platform) · Building Insights: 10,000 free calls a month, then from US$10 per 1,000; Data Layers: 1,000 free, then from US$75 per 1,000

Roof segments, panel counts and yearly energy for existing buildings, for developers building their own tools.

• Building Insights returns the roof segments of a building with their size and orientation, and solar panel configurations with a panel count and yearly DC energy.
• Data Layers return GeoTIFF files: a digital surface model, an aerial or satellite image, annual and monthly flux maps and hourly shade.
• Shading from trees, other buildings and other parts of the roof is taken into account; imagery ranges from 0.1 m per pixel (aerial) to 0.25 m per pixel.

Good to know

• Most values are in DC kWh, independent of panel efficiency; inverter and other losses, soiling and snow are not included, and the values converted to AC use a fixed 85% system efficiency, itself a simplified loss assumption.
• Only existing buildings with imagery are covered, and Google notes that some regions use imagery that is several years old.

Visit Google Maps Platform Solar API

Embrace Ideas · Web app, in the browser · Free plan; paid plans from €59/month (cancellation takes effect after 12 billing cycles) or €599/year, with a 7-day free trial

Checking at concept stage how many real modules fit on a roof, how far apart the rows should be and what they would produce in a year.

• Lays real modules on a flat, single-slope, gable or hip roof inside a 1 m default setback; count and kWp come from the geometry, shown in plan and in 3D, and on flat roofs in a to-scale row section.
• Hourly simulation over the project's weather file, with the row-to-row shading of the spacing actually built; reports monthly and annual kWh, panel area and system size, with specific yield and shading loss in the technical view.
• On flat roofs, optimizers search tilt, orientation and row spacing for the most energy, or for the most energy with every module returning at least 90% of the site optimum (a C4B criterion).
• Part of the Design Direction section of a project, on paid plans; the technical view, with detailed PVGIS, IEC and NREL SAM models and editable losses, is on the Technical and Enterprise plans.

Good to know

• The base view uses a simplified calculation; the technical view refines it with more detailed models.
• Only row-to-row shading is calculated, not shade from neighbouring buildings, trees or roof equipment.
• Pitched roofs are idealised, without valleys, dormers or unequal pitches; there is no string layout, and the results are not part of the PDF report or data downloads.
• The 1 m default setback follows Spanish and Italian fire guidance for defined classes of building; local rules must be checked.

Skelion · Plugin for SketchUp (Windows and macOS) · Free version; Skelion Pro & Support Package US$200 per licence for one year; 15-day trial

Placing solar panels on your own SketchUp model of a roof; shading and yield checks are in the Pro package.

• Inserts solar panels on the roofs of a SketchUp model.
• Listed under the vendor's Pro package: curved roofs, projecting obstructions onto the roof by a distance-to-height or solstice-shadow criterion to find the usable area, and the share of solar energy available to each panel from hourly TMY data, accounting for near shading.
• Also listed under the Pro package: a link from the 3D model to PVWatts and PVGIS for an energy report, and an export of the model to PVsyst.

Good to know

• Needs SketchUp running on the computer; the shading, energy-report and export features above are Pro features, so the free version does less than this list suggests.

Visit Skelion

Valentin Software GmbH · Desktop app (Windows) · €845 per year or €285 for three months (named-user licence, plus VAT); free trial version

Detailed 3D design and yield simulation of rooftop systems with shading from the surrounding objects.

• Buildings are traced from floor plans, cadastral maps or map screenshots and extruded, and roof areas are covered automatically with the maximum possible number of modules.
• Shading is calculated from 3D objects, with up to 7,500 mounted or 10,000 roof-parallel modules shown in 3D.
• Climate data from Meteonorm 9 for any location, orthophotos and elevation data through Google's Solar API, and project reports in 24 languages.

Good to know

• Runs on Windows 10 and 11 only.

Visit PV*SOL premium

PVsyst SA · Desktop app (Windows) · PVsyst 8 Professional CHF 700 per year; student licence CHF 25 per year; one-month free trial

Detailed yield studies and loss reports for grid-connected systems, once the design is being fixed.

• Designs and simulates grid-connected, stand-alone and pumping PV systems, with a final report of the gains and losses.
• The 3D shading scene is modelled in PVsyst or imported from another CAD tool; zones are filled with tables at a set pitch between rows, with exclusion areas.
• Imports meteorological data from Meteonorm 9, NASA POWER, PVGIS, NSRDB, Solcast, SolarAnywhere and Solargis; batch simulations can vary parameters such as row spacing.

Good to know

• Runs only on Windows (8, 10 and 11); the vendor gives separate instructions for Mac users.

Visit PVsyst

Aurora Solar · Design and simulation software for commercial PV · Basic US$159 per month or US$1,620 per year; Pro US$259 per month or US$2,640 per year (per licence, 10 projects a month); Enterprise custom per-project pricing; 14-day free trial

Commercial rooftop layouts with code setbacks, keepouts and row spacing rules, simulated in the same tool.

• Row spacing is set directly or through span-to-rise, ground coverage ratio or a time-of-day rule that keeps the rows unshaded over a chosen date and time window.
• Perimeter setbacks and keepouts with heights around obstructions; its guidance notes that most codes ask for a 4-foot or 6-foot setback on commercial roofs, depending on building size.
• Automatic layout and an hourly simulation that the vendor states is within 1% of PVsyst.

Good to know

• Basic and Pro licences cover one user and 10 projects a month or 120 a year.

Visit HelioScope