Bill of Quantities (BoQ)

A Bill of Quantities (BoQ) is a structured document that itemizes, quantifies, and details all materials, components, and labor needed to construct a solar PV system. In solar projects, the BoQ acts as the central reference for estimating project cost, procurement planning, contractor bidding, and verifying that installations match the engineered design.

A BoQ ensures accuracy throughout the solar workflow—from initial design to procurement and installation—by listing every physical component required, including modules, inverters, racking, cabling, balance-of-system equipment, and mounting hardware. Modern solar design tools often auto-generate a BoQ alongside layout and performance models, especially in platforms like Solar Designing.

Key Takeaways

A Bill of Quantities (BoQ) lists all materials and labor needed for a solar installation.
It supports budgeting, procurement, EPC bidding, and construction planning.
Accurate BoQs reduce material shortages, delays, and cost overruns.
Automated tools like SurgePV improve accuracy and eliminate manual counting.
BoQs differ by project size—residential, commercial, and utility-scale.

What Is a Bill of Quantities (BoQ)?

A Bill of Quantities is a detailed construction document that breaks down all components and labor associated with a solar installation. It is used by EPCs, installers, designers, and project owners to:

Understand total material requirements
Validate design accuracy
Prepare procurement budgets
Standardize bids across vendors
Avoid material shortages or over-purchasing
Ensure consistency between design and field installation

In solar projects, BoQs go beyond simple cost lists—they align with design parameters such as stringing, mounting structures, BOS configurations, and interconnection requirements.

How a Bill of Quantities Works

A BoQ is structured into standardized sections that mirror the construction sequence. For solar projects, the process typically works like this:

1. Extract System Design Data

From CAD, 3D models, or platforms like SurgePV, using:

Module counts
String configurations
Racking layouts
Inverter and BOS specifications

2. Categorize Components

Each item is grouped by:

PV modules
Inverters / MLPE
Racking hardware
DC & AC cabling
Conduits, junction boxes
Grounding components
Mounting hardware
Safety equipment

3. Quantify Each Item

Quantities are calculated based on layout and electrical design rules.

For example:

Module count = row count × column count
DC cable length = string distance + inverter home run
Racking rails = module rows × rail length

4. Assign Unit Rates

Used for budgeting, vendor comparison, and cost forecasting.

5. Produce Final Line Items

A structured table of all components required for installation.

6. Validate in the Field

Installers use the BoQ to verify delivered materials and track shortages.

Types / Variants of BoQ in Solar

1. Design-Generated BoQ

Automatically produced from software based on layout and system configuration.

2. EPC BoQ

Includes additional construction items such as trenching, foundations, fencing, and site work.

3. Procurement BoQ

More detailed and aligned with vendor SKUs, ordering units, and manufacturer specifications.

4. Installation BoQ

Simplified version used by field teams to ensure correct material distribution.

How a BoQ Is Measured or Organized

A typical solar BoQ includes measured items such as:

Module Count

Number of PV modules placed in the array.

Inverter/MLPE Count

Quantity and type of inverters, microinverters, or optimizers.

Racking Quantities

Rails, clamps, bolts, posts, and brackets used in mounting.

Cabling & Conduit Lengths

DC strings, AC homeruns, grounding wire, cable trays, etc.

BOS Components

Disconnects, junction boxes, fuses, breakers, combiner boxes.

Labor Hours

Optional but often included for EPC bids.

The level of detail depends on project size and design maturity.

Typical Values / Ranges

Typical BoQ variations across project types:

Utility-scale BoQs can include hundreds of individual components.

Practical Guidance for Solar Designers & Installers

1. Ensure BoQ matches the latest design revision

Always regenerate the BoQ after layout, stringing, or inverter updates.

2. Align the BoQ with actual site conditions

Measurements from Shadow Analysis or on-site surveys may change material requirements.

3. Cross-check BoQ with a BOM

Use the Bill of Materials to avoid discrepancies.

4. Validate racking quantities carefully

Mounting structure items often cause budget overruns if miscalculated.

5. Use BoQ for procurement & vendor comparison

Standardized quantities make vendor pricing competitive and clear.

6. Integrate BoQ with proposal tools

Platforms like SurgePV automate BoQ-driven pricing for faster proposals:

Solar Proposals

7. Include waste factors

Add 2–5% extra for hardware like clips, bolts, and cable.

Real-World Examples

1. Residential Rooftop Solar

A 6 kW system BoQ includes:

15 monocrystalline modules
1 string inverter
30 rail sections
60 mid/end clamps
120 feet of conduit
300 feet of DC wire

2. Commercial Flat Roof System

A 150 kW array includes:

350 modules
3 three-phase string inverters
Ballasted racking components
Walkway pads
Cable tray and supports

3. Utility-Scale Ground Mount

A 20 MW solar farm BoQ includes:

40,000 modules
200 combiner boxes
500,000 ft DC wiring
Tracker rows or fixed-tilt structures
Trenching, fencing, and MV transformers