Castillo Engineering Services is a solar PV industry leader with more than two decades and 10,000 completed projects worth of experience. With a patented four-step planning, approval and quality assurance process, Castillo Engineering serves as the leading permitting partner for solar PV projects. 

Accurate and compliant drawings are critical to getting permits faster, which is the key to our installers’ productivity and profitability. Castillo Engineering utilizes its solar PV experience to help contractors get the fastest permits for installing residential solar panels without the cost or hassle of negotiating permit details with state and local AHJ. Castillo Engineering maintains an industry-leading 98 percent first-time permit approval. 

Multiple Applications

Design to Permit residential plans from Castillo Engineering work for a range of solar applications for single-family homes. Residential solar installation permit plans include: 

  • Roof Mounts
  • Ground Mounts
  • Canopies, Carports, and Pergolas
  • Batteries (Off-Grid and On-Grid)
  • Power Optimizers
  • String/Micro Inverters
  • Solar Pool Heating

Why Castillo Engineering?

Castillo Engineering works with contractors to gather the information needed to effectively plan projects. Then Castillo Engineering uses its decades of solar PV industry experience to meticulously plan projects to meet and exceed local building requirements.  

For projects in areas that accept generic solar panel installation drawings, Castillo Engineering can streamline the planning process by compiling the needed designs so that plans can be submitted quickly. A quick order and quick ship process that includes structural drawings is available, which can speed up the permitting process for projects. 

Many solar PV engineering projects need site-specific, detailed drawings with structural and/or electrical instructions on installing the panels. Every aspect of the project is detailed down to the length of nails used, as well as the exact location of the PV panels. Castillo Engineering also develops project plans with a minimal bill of materials to help minimize costs. 

Our Plans Include

All Castillo Engineering Design to Permit packages include:

Title Page 

  • Project Description
  • Governing Codes
  • Sheet Index
  • Equipment Summary
  • Plot Plan / Parcel Map
  • Vicinity Map
  • Aerial View


for Rapid Shutdown, AC / DC, AC Labeling / DC Labeling, NEC-required Warning Labels, and Labeling Sizing & Material Requirements 

Symbols and System Description Sheet 

Project Plan & Modules
including Module Type, Dimensions & Weight 

  • Array & Roof Area Calculations
  • Roof / Ground Mount Description
  • Anchoring System Spacing
  • Conduit Run
  • Major Equipment Components and Equipment

Anchoring Details 

  • Attachment Detail
  • Weather Proofing
  • Structural Load Calculations (Wind, Snow, Seismic)
  • Racking & Mounting Hardware
  • Foundation Details

Easy Install Wiring Diagrams 

including 3-line Wire Diagrams 

  • Wire Sizing, Conduit Sizing, String Sizing (DC/AC),& Branch Circuit Sizing (DC/AC)
  • Grounding Requirements
  • Point of Interconnection Details (breaker, line-side tap, subpanels, etc.)
  • Ampacity, Conduit, & Voltage Drop Calculations per NEC Standards
  • Inverter Specifications
  • Solar Module Specifications

Specification Sheets 

for Solar Modules, Inverters, & Racking 

Contact Us

Designed to permit plans for upcoming solar PV engineering projects are available from Castillo Engineering by calling (407) 289-2575 or emailing to discuss specific project needs.