What Is Bill of Quantities (BOQ)? Definition & Guide

Key Takeaways

A BOQ lists both materials and labor tasks with quantities and unit rates — unlike a Bill of Materials (BOM), which covers materials only
BOQs include labor hours for each installation activity (racking, wiring, trenching, commissioning), making them a complete project cost document
In competitive bidding and tendering, a standardized BOQ ensures every contractor prices the same scope of work, enabling direct comparison
Accurate BOQs reduce cost overruns by 15–25% compared to lump-sum estimates, because every line item is quantified before work begins
BOQs follow a standard format — item number, description, unit of measure, quantity, unit rate, and line total — making them readable across organizations
EPC contractors and project developers use BOQs as the primary tool for budgeting, procurement, progress billing, and change order management

What Is a Bill of Quantities?

A Bill of Quantities (BOQ) is a structured document that itemizes every material, labor task, and associated quantity required to complete a solar installation project. Each line item includes a description, unit of measurement, estimated quantity, and a unit rate — producing a total cost for that item. The sum of all line items gives the total project cost.

BOQs originated in the construction industry, where quantity surveyors prepare them to standardize contractor bidding. In solar, BOQs serve the same purpose: they translate a design into a priced scope of work that contractors can bid on, project managers can track against, and procurement teams can use to order materials.

A BOM tells you what to buy. A BOQ tells you what to buy, what to do, how long it takes, and what it costs. For any solar project above 50 kW, the BOQ is the financial backbone of the project — it governs procurement, tracks progress payments, and documents every change order.

Types of Bills of Quantities

Materials Only

Material BOQ

Lists all physical components — panels, inverters, racking, wiring, conduit, switchgear, and hardware — with quantities and unit costs. Equivalent to a priced BOM. Used for procurement planning and supplier negotiations.

Labor Only

Labor BOQ

Itemizes every installation task — roof prep, racking assembly, panel mounting, DC wiring, AC wiring, trenching, commissioning — with estimated labor hours and hourly rates. Used for crew scheduling and subcontractor pricing.

Full Scope

Combined BOQ

Merges material and labor into a single document. Each section lists materials followed by the labor to install them. This is the standard format for EPC contracts and competitive tenders, giving a complete project cost picture.

By Work Section

Elemental BOQ

Organizes items by work element rather than trade — e.g., “DC Array,” “AC Interconnection,” “Civil Works,” “Commissioning.” Each element contains its own materials and labor. Common in utility-scale solar and government tenders.

BOQ Structure for a Residential Solar Project

BOQ Section	Typical Items	Unit	Typical Qty (10 kW)	Unit Rate (USD)
DC Array — Materials	PV modules (400 W)	ea	25	$150–250
DC Array — Materials	Mounting rails (3.3 m)	ea	14	$25–40
DC Array — Materials	Mid clamps	ea	40	$2–4
DC Array — Materials	End clamps	ea	10	$2–4
DC Array — Materials	L-feet / roof attachments	ea	28	$5–10
DC Array — Materials	Flashing kits	ea	28	$3–6
DC Array — Labor	Roof layout and racking install	hr	8–12	$45–75
DC Array — Labor	Panel mounting	hr	4–6	$45–75
Electrical — Materials	DC wire (10 AWG PV wire)	ft	150–300	$0.30–0.60
Electrical — Materials	AC wire (6 AWG THWN-2)	ft	50–100	$0.80–1.50
Electrical — Materials	Conduit (3/4” EMT)	ft	40–80	$1.00–2.00
Electrical — Materials	Rapid shutdown device	ea	25	$15–30
Electrical — Materials	String inverter / microinverters	ea	1–25	varies
Electrical — Labor	DC wiring and stringing	hr	4–6	$45–75
Electrical — Labor	AC wiring and interconnection	hr	3–5	$55–85
Commissioning	System testing and commissioning	hr	2–3	$65–95
Permitting	Permit application and inspection	ls	1	$300–800

Total Project Cost from BOQ

Total Project Cost = Σ (Quantity × Unit Rate) for all BOQ line items

Why BOQ Standardization Matters

When a project owner sends the same BOQ to three contractors, each contractor prices the identical scope. This eliminates ambiguity — no contractor can claim they “didn’t include trenching” or “assumed a different conduit type.” The BOQ becomes the single source of truth for what the project includes, enabling genuine apples-to-apples comparison. For solar EPCs responding to commercial or utility-scale tenders, the BOQ format is often mandated by the client or follows RICS (Royal Institution of Chartered Surveyors) standards.

Practical Guidance

Generate BOQs directly from the design. Solar design software that produces BOQs from panel layouts and electrical configurations eliminates manual quantity takeoffs and reduces errors. Every clamp, wire run, and conduit length should come from the model, not from a spreadsheet template.
Include labor hours in the BOQ, not just materials. A material-only list is a BOM. A proper BOQ pairs each material section with the labor required to install it. This gives project managers a complete cost picture and allows accurate scheduling.
Standardize item descriptions and units. Use consistent naming — “PV Module, 400 W, Mono PERC” not “solar panel” in one line and “module” in another. Consistent descriptions prevent procurement confusion and make BOQs comparable across projects.
Add contingency as a separate line item. Include a 5–10% contingency for materials (waste, breakage) and 10–15% for labor (weather delays, site conditions). Show this as a visible line item, not hidden in unit rates.

Use the BOQ as a procurement checklist. Order materials against the BOQ line by line. When items arrive, check them off against the BOQ quantities. This catches shortages before the crew arrives on site, not during installation.
Track actual vs. estimated quantities. After each project, compare BOQ quantities to actual usage. If the BOQ estimated 150 ft of DC wire and you used 190 ft, update your estimating assumptions. This feedback loop improves BOQ accuracy over time.
Use BOQ sections for progress billing. Bill the client by completed BOQ section — “DC Array materials and installation: 100% complete” — rather than by percentage of total contract. Section-based billing is more transparent and easier to verify.
Document change orders against the BOQ. When scope changes, add or modify specific BOQ line items with revised quantities and rates. This keeps a clear audit trail of what changed, why, and what it cost.

Use BOQ-backed proposals for credibility. Solar proposal software that generates proposals from a detailed BOQ shows the customer exactly what they are paying for. Itemized pricing builds trust compared to a single lump-sum number.
Present a summary BOQ, not the full document. Homeowners do not need to see 80 line items. Summarize the BOQ into 5–7 categories (panels, inverter, racking, electrical, labor, permitting, monitoring) for the proposal, with the detailed BOQ available on request.
Justify pricing differences with the BOQ. When your quote is higher than a competitor’s, open the BOQ: “We’re using 28 flashed roof attachments rated for 25 years. Ask the other installer how many they use and what type.” Specific material and labor details win the comparison.
Feed accurate BOQ costs into the financial model. ROI and payback calculations are only as good as the cost input. A BOQ-derived cost is more accurate than a $/W estimate, producing financial projections that hold up after installation.

Generate Complete Bills of Quantities from Your Design

SurgePV produces detailed BOQs — materials, labor, and costs — directly from your solar design software layout and electrical configuration.

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Sources & References

Frequently Asked Questions

What is the difference between BOM and BOQ in solar?

A Bill of Materials (BOM) lists only the physical components needed for a solar project — panels, inverters, racking, wire, conduit, and hardware — with quantities. A Bill of Quantities (BOQ) includes everything in the BOM plus labor tasks, labor hours, unit rates, and total costs for each line item. The BOQ is a complete cost document used for bidding and project management, while the BOM is a procurement and inventory document.

What does a solar BOQ include?

A solar BOQ typically includes: DC array materials (panels, racking, clamps, roof attachments), DC array labor (layout, racking installation, panel mounting), electrical materials (DC wire, AC wire, conduit, disconnects, rapid shutdown devices), electrical labor (stringing, AC interconnection), inverter equipment, monitoring hardware, commissioning labor, permitting costs, and contingency allowances. Each item has a unit of measure, quantity, unit rate, and line total.

How do you create a bill of quantities for solar?

Start with a completed solar design that defines panel count, layout, inverter configuration, and conduit routing. From the design, extract material quantities — number of panels, rail lengths, clamp counts, wire lengths, conduit runs. Then add labor estimates for each installation phase based on crew size and historical production rates. Apply current unit rates from supplier quotes and labor cost data. Solar design software with auto-BOQ features can generate this automatically from the design model, eliminating manual quantity takeoff and reducing errors.