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Step-by-step rooftop design guide. This page works offline, including when opened directly from your computer.

Solar One: 25 kW On-Grid Rooftop PV Plant Tutorial

Welcome to Solar One! This comprehensive tutorial will guide you through designing a complete 25 kW on-grid roof-mounted solar power plant on a 3,000 sq ft area.

You will learn how to use the portal's tools to move seamlessly from drafting to final energy simulation.

Step 1: Site Setup

Before drawing, define the geographical location of your plant to ensure accurate sun paths and weather data.

  1. Navigate to the Site tab in the workflow bar at the top of your screen.
  2. Use the Search feature to find your location (e.g., city or exact coordinates) or enter the latitude/longitude manually.
  3. Optional: Use the Site tools to place trees or surrounding buildings that might cast shadows on your roof.

Step 2: Drafting the Roof (3,000 sq ft)

A 3,000 sq ft roof is approximately 280 square meters (e.g., a 20m × 14m rectangle).

  1. Switch to the Roofs tab.
  2. Select the Rectangle or Polygon tool from the toolbar.
  3. Click on the 2D canvas to drop your first corner. Drag your mouse to set the dimensions.
  4. If using the Polygon tool, click to drop corners and press Enter (or double-click) to close the shape.
  5. In the Inspector Panel (right side), set the Building height (m) to define the elevation of your roof from the ground.
  6. Tip: You can use the Freehand tool to quickly sketch an irregular roof. Once sketched, you can enter exact dimensions in the precision draft box in the inspector before clicking Finish exact roof.

Step 3: Placing Solar Panels (Layout)

Now we will place approximately 25 kW of solar capacity. Assuming you use 550 W modules, you will need about 45 to 46 panels.

  1. Switch to the Layout tab.
  2. Select your drawn roof by clicking on it.
  3. You have two options for placing panels:
  1. Orientation & Tilt: Adjust the Panel tilt (°) and Orientation (Portrait/Landscape) in the inspector. For RCC roofs, adjust the table rotation to face true south.
  2. Clearance: Use the Obstruction tool to draw AC units, skylights, or vents on the roof. Solar One will highlight any panels overlapping with obstructions in amber.

Step 4: Engineering & Equipment Selection

Next, we map the physical layout to actual electrical components.

  1. Switch to the Equipment tab.
  2. Select Module: Click to select a 550 W module from the supplier library.
  3. Select Inverter: Choose a 25 kW on-grid inverter (e.g., a string inverter with 2 to 4 MPPTs).
  4. Place Balance of System (BoS) components:

Step 5: Cabling & Stringing

Solar One automates the complex task of DC stringing based on your inverter limits.

  1. Still in the Equipment tab, ensure your panels and inverter are placed.
  2. Click Auto-string.
  3. The engine will automatically group your 46 modules into optimal electrical strings (e.g., two strings of 15 and one string of 16) subject to the selected equipment and temperature limits. Review every resulting check; this example is not a guaranteed string assignment.
  4. The system will draw the DC cables along the roof to the inverter. It will also calculate voltage drop automatically.
  5. Review the Electrical Status in the inspector. Green checkmarks mean the implemented screens passed with the entered assumptions. They do not establish engineering approval or installation safety.

Step 6: Structural & Wind Engineering

Review the mounting assumptions and obtain project-specific structural and supplier evidence.

  1. Switch to the Structure tab.
  2. Define the mounting structure settings (e.g., rail sizes, clamps, pedestal heights).
  3. Review the Wind Load checks (IS 875-3). The portal calculates wind pressure based on your roof height and panel tilt.
  4. Ensure no red warnings remain regarding uplift or structural failure.

Step 7: Energy Simulation & Reporting

Finally, forecast how much energy your 25 kW plant will produce annually.

  1. Switch to the Energy tab.
  2. Choose monthly climate or load/import hourly weather for your site. Confirm the source, location and weather period before running the model.
  3. Click Simulate Generation.
  4. The engine performs a full 3D shading analysis (calculating shadow losses from trees and parapets) and generates a detailed yield report.
  5. Switch to the Report tab.
  6. Here, you can review the specific yield (kWh/kWp), Performance Ratio (PR), and total annual MWh generation.
  7. Click Export Drawing PDF to generate an A3/A4 professional plan set, and export the comprehensive calculation package.

Step 8: Exporting to CAD (DXF/OBJ)

For professional workflows, you can export your solar design to standard CAD software.

  1. Save your design and review all failed checks and unresolved engineering issues before exporting.
  2. Click the Export menu in the top navigation.
  3. Select Export DXF for a 2D line-drawing of the roof, panels, and obstructions, which can be opened in AutoCAD.
  4. Select Export OBJ to export the full 3D model of your plant (including building height and metal sheds) for rendering in software like SketchUp or Blender.

Troubleshooting Common Errors

You now have a preliminary design and simulation package. Independent engineering review is still required before construction. Selected-year energy is a weather scenario; it does not establish P50/P90.