How to Compare Solar EPC Quotations from Different Companies

Solar EPC quotations should be compared only after their capacity basis, design assumptions, equipment, construction scope, programme, warranties and exclusions have been normalised. The lowest headline price can represent a different plant, a smaller delivery boundary or a more optimistic generation model.

A defensible evaluation separates technical compliance from commercial comparison, records every clarification and converts the selected bid into a contract with measurable acceptance criteria. The following method helps owners compare like with like.

Decision input	Why it matters	Evidence to request
Operating requirement	Defines the technically suitable option	Site brief and use case
Environment and access	Changes equipment and execution scope	Survey and layout
Performance basis	Prevents an incomplete comparison	Data sheet and design assumptions
Commercial scope	Separates price from exclusions	Itemised quotation
Handover	Supports reliable operation	Test and documentation plan

Normalise Every Bid to One Project Basis

Issue the same site data, capacity basis, drawings, interconnection assumptions, owner requirements and commercial template to every bidder. Ask bidders to return a compliance statement and a list of deviations. Without one bid basis, a lower total can reflect a smaller scope, different equipment or optimistic assumptions rather than better value.

Somaya Solar’s solar EPC service page outlines its current engineering, procurement and construction context. Use that information to frame questions, but require the project proposal to state the exact DC capacity, AC capacity, layout, energy model and delivery boundary being offered.

Compare Design and Generation Assumptions

Place each bidder’s weather data, irradiation, shading, soiling, temperature, mismatch, wiring, inverter, clipping, availability and degradation assumptions in one table. Compare monthly production, specific yield and performance ratio. Ask for the simulation file or a clear report that identifies the model inputs and layout revision.

A higher forecast is not automatically a better proposal. If two bidders use different loss factors or DC-to-AC ratios, adjust the comparison or request a rerun on common assumptions. Confirm whether export, curtailment and plant downtime are included in the financial model.

Review Equipment as an Integrated System

Compare module, inverter, structure, cables, switchgear, monitoring, earthing, lightning protection and safety equipment as one design. Record makes, model families, ratings, certifications, warranties, compatible accessories and substitution rules. A tier label or headline warranty does not prove suitability for the site.

Somaya Solar also describes turnkey solar EPC solutions. For a turnkey comparison, check whether civil, structural, electrical, approvals, metering, monitoring, testing and documentation are included or excluded at the quoted boundary.

Separate Price into Comparable Work Packages

Break the price into engineering, major equipment, balance of system, structure, civil works, installation, access, logistics, approvals, testing, monitoring, spares, training and taxes. Record provisional sums, client-supplied items and quantity assumptions. This exposes scope gaps before they become change orders.

Compare payment milestones against delivered value and project risk. Large advance payments, ambiguous supply milestones or commissioning payments without acceptance criteria change the commercial profile. Include bid validity, price adjustment, delay responsibility, insurance and security requirements in the review.

Test the Programme and Execution Plan

A credible programme should include surveys, design submissions, approvals, procurement, manufacturing, logistics, site readiness, installation, grid or utility coordination, testing and handover. Check long-lead equipment and dependencies on shutdowns, roof availability, crane access or civil completion.

Ask for the proposed project organisation, site supervision, safety plan, quality plan and subcontracting strategy. Somaya Solar’s projects page can provide portfolio context, but the evaluation should focus on experience relevant to the current technology, capacity, site type and execution constraints.

Compare Guarantees, Warranties and Acceptance

Distinguish manufacturer product warranties from EPC workmanship warranties and performance commitments. Define the test conditions, measurement method, exclusions, correction process and remedy for any guaranteed output or performance ratio. Vague performance language is difficult to enforce.

Handover should include approved drawings, data sheets, test reports, settings, warranties, serial records, manuals, training and an open-item list. Confirm who owns warranty coordination and service response after commissioning, especially when products come from multiple manufacturers.

Use a Weighted Evaluation, Not the Lowest Total

Score technical compliance, generation basis, equipment, execution method, programme, safety, quality, team, warranty, service and commercial terms before price. Apply mandatory pass/fail conditions to material safety, legal or technical requirements. The weighting should reflect project risk and owner priorities.

Review Somaya Solar’s about page for company context and use the contact page to clarify proposal assumptions. Record clarification answers in an addendum so the final comparison and contract use the same scope.

Plan the Survey and Data Collection

A site survey should turn assumptions into usable project data. Record dimensions, equipment locations, access limits, utilities, environmental conditions, operating windows, existing controls and photographs from the locations that affect the work. Where measurements are relevant, record method, date, instrument and abnormal operating conditions so the basis can be reviewed later.

A survey is also the right time to identify conflicts that do not appear on drawings: recent additions, obstructions, restricted work areas, damaged equipment, poor access, drainage, heat sources or temporary operations. Resolve material uncertainties before procurement, because a late site discovery often becomes a cost, programme and safety problem.

Use Clear Technical Submittals

A good technical submittal links every offered item to the approved requirement. It should state model or construction, rating, operating limits, dimensions, materials, interfaces, included accessories, installation needs, certifications where required and explicit deviations. Catalogue pages without a compliance statement are not enough for a project decision.

Reviewers should be able to see whether the offer satisfies the site brief without inferring missing information. If an alternative is acceptable, preserve its commercial and technical consequences in writing. This keeps value engineering visible and avoids an apparent like-for-like substitution that changes the delivered result.

Coordinate Interfaces Before Work Starts

Most execution delays occur at interfaces: power and controls, civil works and equipment, supplier and installer, access and operations, or testing and final handover. Assign one owner for each interface and record the prerequisite information, drawings, approvals and dates.

A short interface register is useful for complex sites. It can cover utilities, supports, cables, shutdowns, safety permits, lifting, materials storage, access equipment and owner-supplied items. Review it during procurement and before mobilisation so that the team does not arrive with a technically correct product but no practical route to install it.

Control Quality During Installation

Quality control should happen while work remains visible. Inspect critical dimensions, connections, sealing, supports, labeling, protective measures and settings before covers are closed or work is placed in service. Use the approved drawings and inspection plan rather than relying on visual familiarity with the product.

Record defects and close them with evidence. The objective is not paperwork for its own sake; it is to preserve traceability for items that will be difficult to inspect later. Photographs, test results and serial or batch identities help an owner maintain, troubleshoot and safely modify the installation.

Prepare for Safe Operation and Maintenance

A completed installation must be usable by the people who will operate and maintain it. Confirm safe isolation, clear access, labels, operating limits, inspection points, consumables, spare requirements and escalation contacts. Do not treat maintenance access as an optional extra that can be solved after equipment is commissioned.

The maintenance plan should distinguish routine checks from tasks requiring qualified personnel or specialist tools. It should state what normal condition looks like, which readings or inspections indicate a problem, and what records must be retained. This supports reliable service and reduces unplanned intervention.

Build a Realistic Programme

Programme planning should include design review, approvals, manufacturing or sourcing, delivery, site readiness, installation, testing, correction of defects and handover. Include the dependency on client decisions, access permits, shutdowns and third-party work rather than presenting only an optimistic delivery date.

Where operations cannot stop, phase work by area or function and define the conditions for each handback. A phased programme needs temporary controls, communication and clear acceptance points. It should explain how partially completed work is made safe and how the final system is tested as a whole.

Compare Ownership Cost as Well as Capital Cost

Capital price is only one part of ownership cost. Energy, consumables, service labour, access equipment, downtime, warranties, spares, replacement lead time and expected operating life can materially affect the decision. Use operating data and documented assumptions instead of generic percentage claims.

A supplier may offer a lower purchase price with a smaller scope, shorter warranty or higher service burden. An evaluation table makes those differences visible and gives procurement teams a defensible basis for selection. Where numbers are uncertain, record the assumption and sensitivity rather than hiding it.

Complete Handover with Usable Evidence

Handover should provide the owner with documents that make the asset operable: approved drawings, data sheets, installation details, test evidence, manuals, warranties, settings, training records and a list of open items. The package should identify the final installed configuration, not a pre-award proposal.

Before final acceptance, verify that the agreed tests have been completed, defects have an owner and target date, and maintenance teams can locate the records. A disciplined closeout protects the investment long after the delivery team has moved to another project.

Document Assumptions and Exclusions

Every proposal should state the information supplied by the client, the conditions assumed at the site and the work expressly excluded. Examples include unseen services, third-party permits, off-hours access, structural changes, specialist testing, civil alterations and work outside the defined boundary. Clear assumptions make the price and programme meaningful.

If an assumption changes, assess its effect before continuing. A disciplined change note can identify the technical impact, cost, time, safety consequence and approval needed. This protects all parties from informal scope expansion and preserves a defensible record of the final delivered work.

Use Acceptance Criteria That Match the Intended Result

Acceptance criteria should be agreed before delivery, not invented at the end of commissioning. They may include drawing review, dimensional checks, functional tests, recorded settings, performance evidence, safety checks, training and complete documentation. The criteria should be practical, measurable and proportionate to the risk.

Avoid accepting a system merely because it powers on or appears complete. The owner should be able to confirm that the required interfaces operate, critical conditions have been tested and known defects are controlled. This turns handover into a controlled transfer of responsibility rather than an administrative milestone.

Keep Communication Structured During Delivery

Regular coordination meetings work best when they focus on open decisions, constraints, changes, safety conditions, upcoming access and evidence required for acceptance. Use concise action logs with owners and due dates. This is particularly important where design, supply, installation and operations teams are different organisations.

Escalate issues early when they can still be resolved through a drawing change, alternative product, revised sequence or additional survey. Waiting until a delivery arrives or a shutdown begins can turn a manageable design question into lost time and avoidable disruption.

Manage Risk Before It Becomes Rework

Review foreseeable technical, operational and commercial risks at the beginning of the work. Typical examples are incomplete inputs, long-lead components, access restrictions, unsuitable environmental conditions, unclear ownership of interfaces and insufficient testing time. Give each material risk an owner and a practical mitigation.

A risk register should be revised as site information improves. It is not a replacement for competent engineering or safe work planning, but it helps the team decide what must be resolved before purchase, mobilisation or energisation. Closing a risk should require evidence, not an assumption that it has disappeared.

Support Decisions with Traceable Records

Decision records should show what was approved, by whom, on what basis and which revision controls the work. Store the chosen technical data, deviations, correspondence and test evidence in an accessible location. This is valuable when personnel change or the asset is modified years later.

Traceability also improves dispute avoidance. When a question arises about performance, material selection or scope, the team can review the agreed basis instead of relying on memory. Keep the record concise and relevant so it remains useful to operations rather than becoming an unread archive.

Plan for Future Changes

Facilities evolve: layouts move, loads increase, operating hours change and control systems are upgraded. Where practical, leave safe access, reasonable capacity, spare routes and documented interfaces for foreseeable changes. Future readiness is not unlimited oversizing; it is deliberate planning for likely modifications.

At handover, identify conditions that should trigger a review, such as expansion, new process equipment, repeated alarms, changes in environmental exposure or a major electrical or civil alteration. A timely review is usually less disruptive than correcting an assumption after a failure or shutdown.

Review the Complete Scope Before Purchase

Before issuing a purchase order, reconcile the final technical schedule, approved deviations, commercial terms, programme, interfaces and acceptance plan. Confirm quantities, units, version numbers, delivery location, packaging, inspection rights and responsibilities for offloading, storage and protection.

This final review prevents common failures such as buying an accessory without its compatible interface, approving a product without installation information or omitting a test that the owner expects at handover. A short pre-award review is usually faster than resolving an incomplete scope after delivery.

Use Lessons Learned to Improve the Next Project

Capture what worked and what caused avoidable delay: missing data, difficult access, unclear drawings, unsuitable sequencing, product lead times, commissioning issues or documentation gaps. Translate the lessons into a revised enquiry template, standard detail, acceptance checklist or supplier evaluation point.

Continuous improvement is most useful when it changes a repeatable process. Keep lessons specific, evidence-based and assigned to an owner. This helps future projects begin with better information and reduces dependence on individual memory or last-minute correction.

A Practical Buyer Checklist

• Describe the site, duty, quantity, operating constraints and target outcome in one written enquiry.
• Request exact make, model or construction detail, technical schedule, inclusions, exclusions and delivery basis.
• Compare technically compliant offers before comparing headline prices.
• Freeze approved substitutions, installation responsibilities, tests and handover records before award.
• Retain drawings, data sheets, inspection records and maintenance information with the asset file.

Frequently Asked Questions

1. Why can solar EPC quotes differ so much?

Capacity basis, equipment, losses, civil work, approvals, warranties, programme and exclusions may differ even when totals look comparable.

2. Should the lowest quote win?

Not automatically. First confirm technical compliance and complete scope, then compare risk-adjusted commercial value.

3. What is specific yield?

It is estimated or measured energy output per installed unit of DC capacity over a stated period.

4. Why compare DC and AC capacity separately?

Their ratio affects inverter loading, clipping, equipment count and energy behaviour.

5. How should generation forecasts be compared?

Use common weather and loss assumptions, the same site layout basis and transparent monthly results.

6. Are module warranties enough?

No. Review inverter, structure, balance-of-system, workmanship and performance obligations as well.

7. What is usually excluded from a quote?

Exclusions vary; common examples include structural strengthening, utility charges, owner cabling, taxes, access and unforeseen civil work.

8. How should substitutions be controlled?

Require written technical equivalence, warranty impact, price adjustment and owner approval before purchase.

9. What should be tested at commissioning?

Electrical safety, protection, equipment operation, monitoring, communication, documented settings and agreed performance evidence.

10. How can bidders be scored fairly?

Use one compliance sheet, a weighted evaluation and written clarification records before opening or normalising price.

11. What documents should be part of the contract?

Final scope, drawings, equipment schedule, programme, price breakdown, clarifications, guarantees, tests and handover requirements.

Convert Competing Quotes into One Defensible Project Decision

Issue one comparison template and require every bidder to close material deviations before final evaluation. Explore Somaya Solar’s EPC capabilities, then submit the site brief through its verified contact page and request an itemised, assumption-led proposal that can be evaluated against the same owner requirements.