Most owners spend weeks on the commercial pages of an EPC contract and an afternoon on the technical annexures. The annexures are where a later argument will be settled. Is that inverter acceptable? Did approving a drawing move the design risk? Which documents must the contractor hand over before the last payment?
This guide is part of our solar engineering hub. It is written for developers and asset owners who are drafting or reviewing a solar EPC contract technical specification. It gives an engineer’s checklist for the owner’s side of the table. Its worked source is one public utility tender, read in the sections that matter to an owner. Its examples are not a template for your project.
Quick answer. A solar EPC contract technical specification works only if its schedules fix eight things: interfaces, design basis, equipment ratings and standard editions, design approval rights, inspection plans, test procedures, contracted PR and liquidated damages (LD), and a handover document list tied to payment. Attach each schedule before signing, size LD against the revenue it must replace, and have counsel review the wording.
What belongs in a solar EPC contract technical specification?
Naming varies between contracts. Some call the volumes a technical specification, some call them schedules or annexures. What matters is that each of the eight items below exists as a numbered attachment to the contract. It should not be a promise to agree it later.
| # | Schedule | What it fixes | Question the owner should be able to answer |
|---|---|---|---|
| 1 | Scope and interfaces | Who supplies, builds and connects each item, and by when | Does every owner-supplied item and third-party work have a date and a consequence if late? |
| 2 | Design basis and site data | Site conditions, design life, loads and loss assumptions | Which values are binding minimums and which are only reference? |
| 3 | Equipment specifications | Ratings, standards, tests and warranties | Can two bids be compared line by line? |
| 4 | Design deliverables and approvals | Document list, submission order, review rights | Who can stop work on a drawing, and within what time? |
| 5 | Quality and inspection | Inspection categories, hold points, witness notice | Which items does the owner witness before dispatch? |
| 6 | Testing and commissioning | Procedure, sample, acceptance criteria, punch list | Is the procedure attached before signing? |
| 7 | Performance commitments | Contracted PR, availability, LD | Does the LD pay for the loss it is meant to cover? |
| 8 | Handover and warranties | As-built set, manuals, certificates, spares, defect periods | Is final payment tied to the handover set? |
The sections below take them in contract order. A clause-by-clause checklist follows after them.
What does a public tender show about how these schedules are built?
The Solar Energy Corporation of India (SECI) publishes its tender volumes. Tender SECI/C&P/OP/11/013/2023-24, dated 6 March 2024, covers a 300 MW (AC) ground-mounted plant at Ramagiri, Andhra Pradesh. We opened its technical volume (Section VII) and its contractual volume (general and special conditions) on 31 October 2026.
Section VII is split in two. Sub Section A holds the scope of works, an indicative engineering and design schedule, a delivery schedule and an equipment inspection category list. Sub Section B holds the technical specifications. Its annexures cover the performance test procedure, mandatory spares, plant documentation and commissioning tests, quality plans for civil and mounting works, the O&M agreement and indicative drawings.
Two cautions apply. First, this is a utility owner’s paper for a very large plant, and a C&I owner will not need most of its annexures. Second, its numbers belong to that site and that tender. Use it to see how a clause is worded, not to copy a value. We found no MNRE model EPC technical schedule during this research, and we did not open an NTPC EPC tender.
How should the scope and interface schedule be written?
An interface is any point where the contractor depends on the owner or a third party. Owner-supplied modules, land access, grid connection works and water and power for construction are the usual ones.
The SECI tender shows the pattern. The owner supplies the PV modules at site between 6 and 11 months from award. The EPC contractor then unloads, inspects and stores them, and carries insurance from the date of delivery. The tender also puts the topographical survey (30 days from award) and the geotechnical investigation (60 days) on the contractor. The Employer is not responsible for variations and pays no compensation for them.
Read that as a lesson in allocation. The tender chose where the risk sits and wrote the dates down. Your contract should do the same for each interface, including what relief the contractor gets if the owner is late.
Contract price matters here too. Clause 53.1 of the same general conditions treats the work as lump-sum and firm price. It refuses price or time changes for scope that emerges in detailed engineering. If you adopt that stance, the scope schedule has to be complete. If it is not, the contractor will price the gaps into the bid, or claim them later.
What should the design basis and equipment specification fix?
The design basis states the site conditions the design must survive. The SECI table lists a design ambient temperature of 50 °C and a basic wind speed of 33 m/s (IS 875 Part 3). It adds seismic Zone II (IS 1893 Part 1), rainfall of 75 mm/hr for drainage and a 25-year design life. Those are Ramagiri values. Your own site needs its own sourced values, and the schedule should name the source of each.
The tender also asks for a yield simulation report to be submitted with the design basis report, using module data the owner supplies. That is a good habit to copy. It fixes the loss assumptions on paper before any drawing is approved, so the later performance test has something to be compared with. Our bid-stage vs IFC-stage engineering comparison shows what each stage should contain.
For equipment, the SECI technical volume shows how specific a clause can be.
- Rating condition. The rated AC capacity of the power conditioning unit (PCU) is its output at 50 °C.
- Efficiency and quality. European efficiency of at least 98% and total harmonic distortion under 3% at full load.
- Loss limits that feed the yield. Average DC cable voltage drop is limited to 1.5% of rated voltage for central inverters and 0.5% for string inverters. The contractor supplies the calculation as a spreadsheet.
- Registration. Inverters must be registered with the Bureau of Indian Standards (BIS) under the compulsory registration order the tender cites.
Now the catch. The same volume carries a disclaimer. It says the equipment specifications are “for the reference only” and may be revised to suit the contractor’s design, to the Employer’s satisfaction. It also says components not named but needed to complete the plant are in the bidder’s scope. A contract needs a rule for which values are binding minimums and which may move. Without one, every deviation becomes a negotiation.
Which edition of a code or standard applies?
The two sources we read disagree, and that is worth fixing in writing. SECI’s general conditions (clause 53.3.1) apply the edition current at the date of bid submission unless the contract says otherwise. The Central Electricity Authority (CEA) construction regulations of 2022 say design, construction and testing shall follow the latest version of the relevant BIS or reputed international standards. BIS prevails where the two conflict (Regulation 3(5)(a)). The regulation applies to generating companies, transmission and distribution licensees, the CTU and STUs (Regulation 1(2)). Whether it reaches your specific plant is a question for counsel and for the authority that inspects it.
Whatever applies, name each standard with its edition and year in the schedule, and say which governs on conflict. Regulation 3(6) also expects a quality assurance programme agreed between owner and supplier. Both points come from the Gazette text of the CEA Technical Standards for Construction of Electrical Plants and Electric Lines Regulations, 2022 (notification CEA-TH-17/1/2021, 23 December 2022). We could not reach the CEA website from our environment, so check for later amendments there.
The tender also names the CEA connectivity regulations of 2007 as amended, and the CEA metering regulations of 2006, as requirements for the plant. We read those references in the tender but did not open the regulation text, so this guide cites no numeric requirement from them. See our CEA connectivity glossary entry for the topic.
What design review and approval rights should the owner keep?
This is the schedule where an owner’s engineer earns the most, because a missed review cannot be recovered after construction. The SECI technical volume sets out a clear sequence.
- The contractor submits a design basis report, a PERT chart to at least three levels and a master drawing list for approval before detail engineering starts.
- Every drawing and document goes to the Employer for review and approval. Drawings come in editable format, and spreadsheet calculations come with a working copy.
- The Employer returns each one with a category: I Approved, II Approved subject to comments, III Not approved and resubmit, IV Kept for record, or IV(R) Resubmit for record.
- A note says approval does not relieve the contractor of its obligations for correct design, drawings, quantities, performance and conformity with the specification. It also does not limit the Employer’s rights.
The general conditions back this up. Clause 53.2.1 makes the contractor responsible for errors in its documents whether or not the Project Manager has approved them. Clause 55.3 says the Project Manager reviews drawings as far as practicable within 10 working days. Clause 55.2 gives the contractor 7 working days to resubmit. A contractor delay in rectifying a drawing does not move the completion date.
Note the soft wording in the review period. A review time of “as far as practicable” binds nobody. If the owner’s review is slow, the usual consequence is a claim for time. So the owner’s side needs a named reviewer, a log of every submission and a calendar. That is a staffing question as much as a drafting one.
The SECI document list is also worth borrowing. It includes the grid-model files and transient study that the connectivity process needs. It also lists relay setting charts, quality plans for manufacturing and field work, a site safety plan and operation and maintenance manuals. Our relay coordination study guide explains one of those studies, and our single-line diagram glossary entry defines the core drawing.
If your team does not have a reviewer with time for this, Heaven Designs offers MW-scale project management consultancy. Its page describes project management for utility-scale solar from feasibility through commissioning, with design and engineering support and QA/QC among its scope areas. It presents a management, coordination and quality-oversight service. Scope and turnaround are agreed at scoping. Our guide to the owner’s engineer role shows where a design review sits in a project.
What should the inspection and test schedule say?
How should factory inspection be set up?
SECI sorts equipment into three inspection categories. Category A items get a pre-dispatch inspection by both SECI and the EPC contractor. They are the PCU, inverter transformer, HT switchgear panel, power transformer, control and relay panel, mounting structure and SCADA. Category B is inspected by the contractor only. Category C needs no pre-dispatch inspection. SECI reserves the right to inspect B and C items too.
The general conditions add the mechanics. The contractor gives 15 days notice for work inspections and 7 days notice for witnessing factory acceptance tests. The contractor bears inspection costs, the owner bears its own representatives’ travel, and a re-inspection after a failed factory test is at the contractor’s cost.
For your contract, list every major item with a category, say who witnesses, and fix the notice period. Leave the owner a right to inspect any item.
What should the commissioning procedure fix?
Annexure C of the SECI technical volume bases commissioning on IEC 62446. The standard’s consolidated edition, IEC 62446-1:2016+AMD1:2018, defines the documentation to be handed to the customer and serves as a template for it. The tender’s own procedure adds the details a contract needs:
- Modules are stabilised first, after 200 kWh/m² has reached the plane of the array.
- The Owner or its representative witnesses the tests.
- Visual inspection covers 5% of the system. For electrical pre-energising tests, the Owner picks at least 2 strings from 2 string monitoring units per inverter at random, and the sample must pass 100%.
- Defects go on a punch list graded critical, important or minor. In the SCADA and weather station test, the punch list is capped at 1% of construction price.
- Infrared inspection of ground-mount plants covers 100% of modules, inverters and combiner boxes. Pass limits are 0.2% of modules with cell or junction-box hot spots and no potential-induced degradation (PID).
- Inverter availability must reach 99% during its test, and single-axis trackers must stay within 2 degrees of the theoretical angle for 99.5% of operating time.
- Instruments need valid calibration certificates from approved laboratories.
Those thresholds are that tender’s. Your own values need an engineer’s judgement for your plant. Our IEC 62446 acceptance testing guide and commissioning checklist explain the test categories.
For the monitoring system itself, name the class you want under IEC 61724-1:2021. That edition defines monitoring system classes and removed Class C. Our IEC 61724 explainer covers the sensor detail. A performance ratio test is only as good as the sensors behind it.
How do contracted PR and LD mechanics work?
The full test procedure belongs in its own schedule, and we have covered it in our performance ratio test guide, which has a 16-row clause checklist. This section covers what the commercial mechanics do to the owner once the test result exists.
The SECI tender shows five connected mechanisms:
- The commitment. The contracted PR for operational acceptance is 81.50%, measured at the 220 kV side of the pooling substation. That value belongs to that site and that point of measurement.
- The shortfall LD. For every 0.01 of PR below the contracted value, LD of 1% of contract value is levied.
- The cutoff. If the shortfall exceeds 0.05, the plant is accepted as-is and the operational acceptance milestone payment is not made.
- The corrective route. If the first test fails, the contractor gets two more chances after corrective measures.
- The annual commitment in O&M. Annual PR is the mean of monthly PR. If it falls short by up to 5 points, LD equals the shortfall divided by 0.05, times 0.7, times the annual O&M contract value. LD is capped at 70% of that annual value.
Delay has its own LD. Clause 20 of the general conditions sets it at 0.5% of contract price per week with a 5% maximum. When the maximum is reached, the owner may terminate or have the work completed at the contractor’s risk and cost. Separately, GCC 43.3.2 lists settlement of LD for delay and performance among the conditions for releasing the operational acceptance milestone payment.
Does the LD pay for the loss?
Run the arithmetic before you sign. This example is illustrative. Every input is an assumption, and none is a market figure.
| Input or result | Value |
|---|---|
| Plant | 20 MWp DC |
| Plane-of-array irradiation | 1,800 kWh/m² a year |
| Tariff | ₹3.50 per kWh |
| Contract price | ₹90 crore |
| Contracted PR against measured PR | 81% against 78% (3 points short) |
| Energy lost a year | 20,000 kWp × 1,800 h × 0.03 = 1,080,000 kWh |
| Revenue lost a year | ₹37.8 lakh |
| Revenue lost over 25 years (flat tariff, no degradation, undiscounted) | ₹9.45 crore |
| Shortfall LD at 1% of contract price per 0.01 | 3 × ₹90 lakh = ₹2.70 crore |
| LD as a share of 25-year lost revenue | about 29%, or about 7 years of the loss |
| Delay LD at 0.5% a week | ₹45 lakh a week, reaching the 5% cap (₹4.5 crore) in week 10 |
In this case the LD buys about seven years of the revenue the plant will not earn. That may be acceptable, or it may not, but it is a number the owner should have chosen. The result also shows why the corrective route matters. A contractor who fixes the cause removes the loss. An LD only prices it.
Think about three drafting choices. Decide whether corrective work comes first and LD is the fallback. Decide whether the LD counts toward any overall liability cap. In the SECI general conditions, aggregate contractor liability is capped at 100% of contract value, and indirect and consequential losses are excluded (clause 73.15). Finally, decide whether a large shortfall lets you refuse acceptance instead of accepting as-is. For LD structure, insurance and bonds, see our guide to LD, PI insurance and performance bonds.
Which as-built and handover documents should the contract list?
Tie the list to a payment. The SECI general conditions release the operational acceptance milestone payment only after the contractor submits, among other items:
- all as-built drawings and documents;
- the detailed engineering documents, with specifications, schematics, cable routing plans, test results and manuals;
- the bill of materials of the installed plant;
- the inventory of recommended and mandatory spares;
- all approvals and no-objection certificates;
- the list of deviations from approved drawings, with reasons;
- a signed punch list;
- settlement of LD for delay and performance;
- certificates of tests, and warranty certificates for each equipment item.
The technical volume adds detail. As-built drawings must be corrected to actual site conditions and must carry the deviation list from the “good for construction” (GFC) drawings. The general conditions require as-builts to bear a certification stamp signed by both the contractor and the Engineer-in-Charge. After operational acceptance the contractor supplies four hard copies and a soft copy.
The records are not only a contract matter. Regulation 3(8) of the CEA 2022 regulations says the owner shall retain these at the site for the life of the plant: as-built drawings, design memorandum, data sheets, operating manuals, manufacturer warranties, test results and design and construction documents. It also says the owner shall keep those records updated as the system is modified. IEC 62446-1 describes the documentation set that is handed to the customer. Our as-built drawings guide is written around US permit and utility requests, but its change-tracking discipline carries over.
Defect periods deserve their own table in the handover schedule. In the SECI documents, the general conditions set a 12-month defect liability period from operational acceptance. They add a 5-year latent defect liability for design and manufacturing defects. Item warranties in the technical volume run from 1 year for cables to 5 years for PCUs, transformers and control and relay panels. The plant design life is 25 years. Write one table that states each period, when it starts and which clause governs if two differ.
Which red flags should owners look for in a draft?
| Red flag | Why it matters | What to ask for |
|---|---|---|
| ”Good engineering practice” or “latest edition” with no named standard | The test of compliance becomes an opinion | Named standards with edition and year, plus a conflict order |
| Specifications marked reference only with no binding rule | Even the SECI tender carries such a disclaimer. Every deviation turns into a negotiation | A list of binding minimums and the approval route for any change |
| Test procedure “to be agreed before testing” | Both sides will agree to the version that favours them on the day | The procedure attached as a schedule before signing |
| Silence treated as consent. SECI’s GCC 43.3.5 deems the plant accepted if the owner neither certifies nor objects in writing within 30 days | A slow reviewer can accept a plant by default | A named reviewer, a calendar of response dates and a written reservation process |
| Approval language that suggests approval transfers design responsibility | The owner could inherit risk it did not price | A sentence that approval does not relieve the contractor, as in the SECI text |
| Warranty and defect periods stated in several places | The shortest or the latest document may win | One table with start dates and a precedence rule |
| LD that is small beside the lost revenue, plus a low overall cap | The contractor can treat underperformance as a priced option | A worked LD check and a stated rule on how LD counts toward the cap |
| Handover documents promised but not tied to payment | The documents arrive late or never | The SECI-style list tied to the final milestone |
| Owner-supplied items with dates but no relief rule | Delay claims become open-ended | A defined extension and cost rule for each interface |
What is the clause-by-clause checklist?
Use this list as a drafting aid, not as legal advice. Have counsel review the final wording, and confirm project-specific requirements with your lender, utility, DISCOM and the inspecting authority. The right-hand column shows how the SECI Ramagiri tender words the point, so you can see the shape of a clause. Do not copy its values.
| # | Schedule | Write this down | SECI Ramagiri tender (FY 2023-24) |
|---|---|---|---|
| 1 | Scope | Each owner-supplied item, its delivery window, storage and insurance duties and relief if late | Modules supplied 6 to 11 months from award. Contractor unloads, stores and insures from delivery |
| 2 | Scope | Who commissions site surveys and geotechnical work, by what day, and who carries variance | Contractor, 30 and 60 days from award, no compensation for variation |
| 3 | Scope | How scope found in detailed engineering is handled | Lump sum, no price or time change (GCC 53.1) |
| 4 | Design basis | Sourced site values: temperature, wind, seismic, rainfall, design life | 50 °C, 33 m/s, Zone II, 75 mm/hr, 25 years |
| 5 | Design basis | Yield model, weather file and loss assumptions submitted with the design basis report | Simulation report with the report, using owner-supplied module data |
| 6 | Specifications | Which values bind and which are reference | Disclaimer: reference only, revisable to the Employer’s satisfaction |
| 7 | Specifications | Rating conditions, efficiency and distortion limits | PCU rated at 50 °C, efficiency 98% minimum, distortion under 3% |
| 8 | Specifications | Loss limits that feed the yield model | DC voltage drop 1.5% or 0.5%, with a calculation sheet |
| 9 | Specifications | Standard names, editions, years and conflict order | Edition at bid date (GCC 53.3.1) |
| 10 | Specifications | Compliance papers: BIS registration, type test reports | Inverters under the BIS compulsory registration order |
| 11 | Approvals | Document list and submission order, with a master drawing list | Design basis report, PERT chart and master drawing list before detail engineering |
| 12 | Approvals | Approval categories and the non-relief sentence | Categories I to IV(R), approval does not relieve the contractor |
| 13 | Approvals | Review period and what happens if the owner is late | Review as far as practicable within 10 working days, 7 working days to resubmit |
| 14 | Approvals | Editable files and calculation sheets | dwg files, working spreadsheets |
| 15 | Approvals | Who owns errors in approved documents | Contractor, approved or not (GCC 53.2.1) |
| 16 | Inspection | Categories by equipment, owner’s right to inspect any item, notice and cost split | Categories A, B, C. Notice of 15 days and 7 days |
| 17 | Testing | Commissioning standard and edition, witness, sample method, thresholds, punch list classes and cap | IEC 62446 based, owner picks the sample, 100% sample pass, punch list capped at 1% of construction price |
| 18 | Testing | Instrument calibration | Valid certificates, approved laboratories |
| 19 | Testing | Monitoring class and sensor requirements | IEC 61724 referenced for sensors in the SCADA and weather station test |
| 20 | Performance | Test procedure attached as a schedule (use the 16-row PR checklist) | Annexure A of Section VII-B |
| 21 | Performance | LD formula, whether corrective work comes first, cutoff for acceptance as-is | 1% per 0.01, two more chances, as-is above 0.05 |
| 22 | Performance | Delay LD rate and cap | 0.5% a week, 5% maximum |
| 23 | Handover | Document list tied to the final milestone payment | 13 items in GCC 43.3.2 |
| 24 | Handover | As-built certification and the deviation list from GFC drawings | Stamp signed by contractor and Engineer-in-Charge |
| 25 | Handover | One table of defect and warranty periods with a precedence rule | 12-month defect period, 5-year latent defect period, item warranties 1 to 5 years |
What should you do before you sign?
- List which of the eight schedules your draft contract has as numbered attachments. Any missing one is a promise to agree later.
- Mark every value in the specification as binding or reference.
- Name a reviewer for design approvals, give that person the calendar in the checklist and log every submission.
- Attach the performance test procedure and run the LD arithmetic with your own tariff and plant size.
- Write the handover list into the payment milestone.
- Send the marked draft to counsel, and to your lender if there is one.
If the owner side has no one with time for steps 3 and 4, the cheapest moment to add one is before award. Heaven Designs offers MW-scale project management consultancy for utility-scale solar projects. Send us the project details and we will confirm what is in scope. We reply within 1 business day.
FAQ
What is the difference between a technical specification and a technical schedule?
Usage varies between contracts. The SECI tender calls its technical volume Section VII, with a scope of works sub-section, a technical specification sub-section and lettered annexures. Do not rely on the names. Check that each of the eight items is a numbered, attached document.
Does approving a contractor’s drawing move design responsibility to the owner?
In the SECI documents it does not. The technical volume says approval does not relieve the contractor of its obligations. The general conditions keep the contractor responsible for errors whether or not a drawing was approved. Write the same sentence into your contract and ask counsel to confirm the wording.
Can a private owner copy a SECI tender?
You can borrow the structure and the wording of a clause. Do not borrow the values. The SECI figures belong to a 300 MW ground-mounted site, a particular grid interface and a utility’s risk appetite. A C&I rooftop or a smaller ground-mount plant needs its own values.
Do the CEA regulations apply to my plant?
The 2022 construction regulations state that they apply to generating companies, transmission licensees, distribution licensees, the CTU and STUs. Whether a captive or C&I plant is within that scope is a question for counsel and for the authority that inspects the plant. The same goes for which amendments apply today. Name the standards you want in the contract either way.
Do the same schedules apply to a repowering contract?
Yes. A repowering contract needs the same eight schedules, with one difference: the as-built set you already hold becomes the design basis. Our solar plant repowering guide covers the redesign checks, and the CEA records duty in Regulation 3(8) is a reason to keep that set current.