A Bill of Materials (BOM) is the complete, itemized list of all equipment, hardware, and components required to install a solar PV system. It includes everything from solar modules and inverters to mounting hardware, wiring, breakers, connectors, and BOS (Balance of System) components. The BOM ensures that installers, EPCs, procurement teams, and designers know exactly what materials are needed to build the system without delays, shortages, or mismatches.

In modern design platforms, BOMs are often generated automatically using features like Auto-BOM or Auto-Design tools within software such as Solar Designing. A well-prepared BOM helps reduce installation errors, prevent cost overruns, streamline purchasing, and maintain consistency across residential, commercial, and utility-scale solar project workflows.

• A Bill of Materials (BOM) lists every component needed to install a solar PV system.
• Essential for procurement, installation planning, and cost estimation.
• BOMs are generated from layout, stringing, and mounting design workflows.
• Ensures code compliance, installation accuracy, and proper material ordering.
• Software automation greatly improves speed and consistency.

What Is a Bill of Materials (BOM)?

A Bill of Materials is the structured document that lists every physical component required for a solar installation. It outlines:

• Product names
• Quantities
• Technical specifications
• Part numbers
• Electrical and mechanical attributes
• Mounting and BOS hardware
• Optional or project-specific accessories

A BOM acts as a single source of truth for procurement, engineering, warehouse planning, and installation teams.

Related terms that often interact with the BOM include Mounting Structure, Stringing & Electrical Design, and Solar Layout Optimization.

How a BOM Works

1. The design software evaluates the solar layout

Once the module placement is finalized—often using automation tools like Auto-Design—the system calculates the number of modules, rails, and electrical components needed.

2. Electrical configuration is analyzed

Based on stringing, inverter sizing, conductor length, and protection requirements, the BOM adds:

• String inverters or microinverters
• DC/AC disconnects
• Breakers & fuses
• Wiring and connectors

See Stringing & Electrical Design.

3. Mounting hardware is calculated

Roof type, tilt angle, layout density, and structural constraints determine:

• Rails
• Mounting brackets
• Bolts and fasteners
• Clamps
• Ground screws or ballast blocks

4. Balance of System (BOS) components are added

This includes monitoring hardware, conduit, labeling, grounding, and walkway materials.

5. The BOM is exported for procurement and project planning

Teams use the output for purchasing, cost estimation, proposal building, and installation preparation.

For proposal workflows, see Solar Proposal Tools.

Types / Variants of BOMs in Solar

1. Electrical BOM

Covers all electrical components:

• Inverters
• Disconnects
• Breakers
• Conductors
• Rapid shutdown devices

2. Mechanical BOM

Includes structural hardware:

• Racking
• Rails
• Clamps
• Mounting feet
• Fasteners

3. BOS (Balance of System) BOM

Contains all non-module, non-inverter items:

• Monitoring hardware
• Labels & safety materials
• Grounding equipment
• Conduit and fittings

4. Installation BOM

Prepared for field crews, including tools and consumables.

5. Procurement BOM

Used by purchasing teams with exact SKU numbers and vendor-specific details.

How a BOM Is Measured

The BOM is measured using:

Quantity of Each Component

Accurate counts of all modules, inverters, and mounting hardware.

Electrical Load Calculations

Determined during design—see Load Analysis.

Conductor Lengths (ft, m)

Used for estimating wiring needs and voltage drop.

System Power Ratings (kW, kWp)

Impacts inverter count and BOS sizing.

Weight and Structural Loads

Critical for mounting and roof engineering.

Cost Estimation

Used in proposals and ROI calculations—for example, with the Solar ROI Calculator.

Typical Values / Ranges

In most residential projects, the BOM includes 20–50 line items, while large commercial systems may include 200+ components.

Practical Guidance for Solar Designers & Installers

1. Always generate the BOM after finalizing stringing

Electrical adjustments impact wire lengths, fuse requirements, and inverter counts.

2. Confirm all AHJ and NEC requirements

Certain regions require additional labeling, rapid shutdown equipment, or grounding hardware.

3. Use Auto-BOM features when possible

SurgePV automates the full generation process—see Solar Designing.

4. Validate structural components

Roof type (shingle, tile, metal), ballast requirements, and wind/snow loads affect mounting hardware.

5. Share BOMs with procurement early

This avoids supply shortages and delays.

6. Re-check BOM accuracy before installation

Installers rely on precise counts to avoid missing parts during field deployment.

Real-World Examples

1. Residential BOM (7 kW System)

Includes:

28 modules, 1 inverter, 4 rails, 16 mounts, rapid shutdown devices, wiring, grounding kit, labels.

2. Commercial Flat Roof BOM (250 kW System)

Includes:

600 modules, ballasted racking blocks, 6 string inverters, AC/DC disconnects, monitoring hardware, long conductor runs, safety pathways.

3. Ground-Mount Solar Farm (1 MW)

Includes:

2,500 modules, steel mounting structures, piles, combiner boxes, monitoring equipment, trench wiring, medium-voltage gear.

• Solar Layout Optimization
• Stringing & Electrical Design
• Mounting Structure
• POA Irradiance
• Auto-Design