How to Evaluate Solar EPC Bids: A Procurement Checklist

To understand how to evaluate solar EPC bids, normalise every bidder against one requirement, bill of quantities, design basis, responsibility matrix, programme, acceptance plan, O&M scope, and commercial template. Apply technical pass/fail gates before weighted scoring. Compare price only after omissions, exclusions, assumptions, risk transfers, and unresolved deviations are visible.

This checklist is for project procurement teams and qualified technical, commercial, financial, legal, tax, safety, and grid reviewers. It does not provide a universal score weighting, price, yield, warranty, or contract term.

What should be issued to every EPC bidder?

Issue one controlled request with site data, objectives, capacity definitions, surveys, utility information, design criteria, approved makes process, BOQ format, interfaces, exclusions, programme, safety, tests, handover, O&M, commercial schedules, and response instructions. Require bidders to list deviations and data gaps instead of silently creating different assumptions.

The bid package should state:

• project site, access, land or roof rights and available surveys;
• load, connection, metering, export, grid and operating requirements;
• whether capacity means module DC kWp, inverter AC kW, export limit, battery power or energy;
• design life or analysis horizon only where the owner has approved it;
• minimum design, structural, electrical, safety and documentation requirements;
• owner-supplied work, third-party interfaces and authority responsibilities;
• BOQ units and pricing schedule;
• programme milestones and dependency register;
• commissioning, performance and handover requirements; and
• contract, payment, security, insurance, liability and change schedules for review.

Record clarifications centrally and issue the same answer to every bidder where procurement rules require equal information.

How should scope and BOQ be normalised?

Create a master BOQ and responsibility matrix, then map every bidder’s quantity, specification, inclusion, exclusion, unit rate, assumption, and evidence to it. Do not compare lump sums until missing scope, owner-supplied work, provisional quantities, optional items, taxes, freight, application costs, and interface responsibilities have been reconciled.

Track quantities by unit and basis. A bidder can be cheaper because the structure tonnage, cable length, protection, access, grid work, documentation, or O&M scope differs, not because execution is more efficient.

How should technical compliance be checked?

Use pass/fail gates for mandatory site, structural, array, inverter, protection, grid, environmental, safety, monitoring, and documentation requirements. Verify exact models and calculations against current documents. A commercial score or preferred brand cannot offset an unresolved safety, compatibility, authority, or mandatory-performance failure.

Review at least:

1. site survey, layout, shading and access basis;
2. structural loads, interfaces, corrosion environment and waterproofing;
3. module string voltage, current, temperature and MPPT allocation;
4. inverter AC rating, phase, grid interface, environment and communications;
5. cable sizing, routing, isolation, protection, earthing and coordination;
6. transformer, switchgear, meter, CT, plant controller and utility interface where applicable;
7. monitoring points, data ownership, retention, alarms and cyber access;
8. construction method, permits, safety plan and quality records; and
9. exact evidence for every proposed deviation or alternative.

Use the EPC inverter-selection scorecard for the hardware sub-review and the string-sizing guide for the DC calculation record. Neither replaces whole-project engineering approval.

How should generation assumptions be compared?

Put every energy model on the same weather, layout, equipment, capacity, shading, loss, availability, curtailment, grid-outage, degradation, and uncertainty basis. Require monthly outputs and the model file or reproducible report. Separate an engineering estimate from a contractual guarantee, and define how any guaranteed result will be measured and adjusted.

Generation review table:

Do not compare two performance ratio or annual-yield numbers until the boundary, formula, period, data quality, correction method, exclusions, and remedy are the same.

How should programme, commissioning and handover be reviewed?

Review the programme as a dependency network, not only a completion date. Identify surveys, design approvals, procurement, permits, access, shutdowns, civil works, grid and meter activities, installation, testing, defect correction, authority inspection, energisation, performance verification, training, as-built records, and handover, with an accountable party for each dependency.

Ask each bidder to provide:

• logic-linked programme and critical dependencies;
• long-lead equipment and substitution control;
• owner, utility and authority action register;
• inspection and test plan with hold points;
• pre-commissioning, energisation and functional test procedures;
• acceptance criteria and defect-closeout process;
• serial-number, setting, firmware and test-result register;
• as-built drawings, manuals, warranties and training; and
• incomplete-work and punch-list treatment at commercial completion.

The solar inverter commissioning guide explains the inverter evidence subset. An app screenshot or energy reading does not close whole-project commissioning.

How should O&M and responsibility boundaries be compared?

Define who observes, inspects, tests, cleans, responds, diagnoses, repairs, replaces, reports, escalates, and coordinates warranties for every asset and interface. Compare triggers, competence, access, spares, response process, exclusions, parts, labour, travel, monitoring, reports, term, renewal, termination, and the transition from EPC defects to O&M obligations.

Use a responsibility matrix for:

The bid should not use comprehensive O&M without a task, evidence and exclusion schedule. Warranty duration also does not explain labour, freight, site attendance, replacement, or lost-generation treatment.

How should commercial bids be normalised?

Reconcile price after technical and scope normalisation. Identify taxes, duties, escalation, freight, insurance, securities, retention, payment timing, provisional sums, owner costs, finance, working capital, change rules, delay treatment, warranties, liabilities, exclusions, options, O&M, spares, replacements, and end-of-term obligations before comparing the evaluated commercial position.

Use:

Do not display a result if gaps lack quantities or approved valuation rules. Mark the comparison incomplete. Keep risk assessment separate from arithmetic where probability or consequence evidence is unavailable.

For inverter lifecycle scope, the inverter TCO guide provides an input-led worksheet. Obtain legal, tax, insurance and finance review for the project contract.

How should a weighted bid worksheet be built?

Build weights from the owner’s approved objectives and risk, make the total equal 100, define each score before opening commercial bids where governance requires it, and attach evidence to every score. Mandatory gates stay outside the weighting. Sensitivity-test the result so small subjective changes do not silently determine the award.

Worksheet fields:

For each category, calculate the weighted result above, then sum category results only after the score definitions and units are checked. Do not award points for unsupported claims or let the same benefit score in multiple categories.

What should happen before contract award?

Before award, close mandatory deviations, validate references and capability, reconcile scope and price, review design and generation assumptions, confirm authority interfaces, complete legal and financial review, document score sensitivity, and carry every accepted clarification into the final contract. The award recommendation should list conditions, open risks, owners, and required pre-start evidence.

Final checks:

1. Verify legal entity, financial and delivery capability using approved due diligence.
2. Contact relevant references with project-specific questions and consent.
3. Confirm exact equipment, supply route and approved substitutions.
4. Freeze the requirement, BOQ, responsibility matrix and deviation register.
5. Reconcile price, tax, payment, security, O&M and option schedules.
6. Confirm programme dependencies and authority responsibilities.
7. Complete technical, safety, legal, tax, insurance and finance approvals.
8. Issue a reasoned recommendation and retain the evaluation evidence.

Use the datasheet library or contact Qbits for an exact-model inverter review inside the wider procurement process. Set your own scoring weights with project procurement and engineering before applying this framework to live bids.

Sources checked 23 September 2026: current Qbits inverter-selection, string-sizing, commissioning and TCO guides plus current public Qbits datasheets. No bid result, weight, price, yield, service level or contract outcome is claimed.