Two quotations for the same rooftop can look almost identical on page one and behave very differently on your plant floor five years later. One lists named modules, a monitoring system and a performance guarantee. The other offers “Tier-1 panels” at a lower price per Wp. Which is cheaper? You cannot tell until you know what is inside each.
That is the real challenge of how to choose a solar EPC company. The decision is not about price per watt. It is about who designs the plant, which components go on your roof, who guarantees the output, and who answers the call in year six.
The timing adds pressure. MNRE’s ALMM List-II for solar cells applies from 31st December 2026, and net-metering and open-access projects commissioned after this date will not be eligible for any government subsidy/net metering/net billing. Component choices now carry a compliance question as well as a quality one.
This guide gives you nine checks, a quote-comparison table, a scoring matrix and the contract clauses worth locking down.
In this article
- What a solar EPC company actually does
- Before you shortlist: define your requirement
- The 9-point checklist for choosing a solar EPC company
- Red flags in an EPC proposal
- How to compare quotations like for like
- Contract clauses to lock down
- How HCK Solar approaches EPC projects
- Conclusion and next step
What a Solar EPC Company Actually Does
EPC stands for engineering, procurement and construction. A solar EPC company designs your plant, buys the components, builds it, commissions it and hands it over, with one party accountable for the result. For a factory, that single point of responsibility matters. When output falls short, you do not want a module supplier, an inverter vendor, BOS supplier and a civil contractor each pointing towards each other often in case of non-performance.
EPC is a delivery model, separate from the ownership model:
| Model | Who owns the plant | Role of the EPC | Typically suits |
|---|---|---|---|
| CAPEX (own it) | You | Designs, builds, commissions, often maintains | Businesses that want the asset and the full savings |
| OPEX / RESCO | A developer; you pay per unit | The developer usually engages an EPC to build | Businesses that prefer no upfront investment |
This checklist applies to both. Under a RESCO model, ask who the EPC is and what standards they build to, because you will live with the plant either way.
Before You Shortlist: Define Your Requirement
A good solar EPC company can only be as good as your brief. Gather these before you invite quotes:
- Twelve months of electricity bills, with sanctioned or contract demand and tariff category.
- Your daytime load profile. Solar produces in daylight, so shift patterns matter.
- Roof type, age, condition and available shadow-free area, or land if you are considering ground-mounted solar.
- The connection route you expect: net metering, captive or open access, as allowed in your state.
- Your priorities: savings, payback, reliability, ESG reporting, or a mix.
Give every bidder the same inputs. Otherwise you will be comparing assumptions instead of offers.
The 9-Point Checklist for Choosing a Solar EPC Company
Check 1: Check the depth of engineering
A serious EPC starts with a site visit, not a price list. Look for a structural assessment of the roof, a shadow analysis, string and inverter sizing logic, and an energy simulation with stated assumptions.
Ask for the generation estimate and its inputs: irradiance data source, system losses, and the degradation rate used. NREL’s review of nearly 2,000 field measurements found a median module degradation of about 0.5% per year. A proposal assuming no degradation, or an unusually high yield, deserves to be questioned.
Check 2: Verify ALMM and standards compliance
For net-metering and open-access projects, modules must come from MNRE’s ALMM List-I. From 1 June 2026, the cells inside those modules must come from List-II, unless the project was commissioned before 31st December 2026.
Ask the EPC to name the exact module model and show its current ALMM enlistment. Check it against MNRE’s official list, because enlistments change. Also ask for the test certificates behind the components, such as IEC 61215 and IEC 61730 for modules, and the applicable inverter safety standards.
Check 3: Demand a bill of materials with makes and models
The bill of materials (BOM) is where cheap quotes hide their savings. It should name the make, model and rating of modules, inverters, mounting structure, cables, protection devices, earthing and monitoring.
A vendor-neutral EPC picks components on merit for your site and can explain each choice. Be cautious if an EPC will not disclose makes before the order, or pushes one brand without a reason tied to your project.
Check 4: Look for a verifiable track record
Ask for commissioned plants of similar size and type, and visit one if you can. Speak to the plant head, not only the sales contact. Ask whether actual generation has matched the estimate and how those problems were handled.
Megawatts “executed” is a weak signal on its own. Relevant, operating client references are stronger.
Check 5: Assess execution strength and safety
A well-designed plant can still be badly built. Ask who actually does the work: in-house crews or subcontractors, and how they are supervised. Ask about work-at-height safety practices, site supervision, the project schedule and the EPC’s financial ability to complete the job and honour warranty commitment. Confirm the electrical contractor licence and approvals your state requires.
Check 6: Get warranties and performance guarantees in writing
Separate two things. Product warranties come from component makers. Performance guarantees come from the EPC and cover the plant as a system.
Two terms to understand: Performance Ratio (PR) compares actual output with what the installed capacity should deliver under real conditions, and Capacity Utilisation Factor (CUF) is actual output as a share of the theoretical maximum. A guarantee should state which metric applies, how it is measured, over what period, and what the EPC pays if it is missed.
Illustrative example (assumed numbers, not a promise): take a 500 kWp plant with an assumed 1,400 kWh per kWp per year, so 7,00,000 kWh a year. If actual output is 5% short, that is 35,000 kWh. At an assumed ₹8 per kWh of avoided grid cost, the annual loss is about ₹2.8 lakh. Over many years that is real money, and that is why the guarantee clause matters more than a small price difference.
Check 7: Inspect quality assurance and commissioning tests
Ask for the quality plan: incoming material inspection, structure and anchoring details, DC and AC cable routing, earthing and lightning protection, and roof waterproofing at mounting points. Ask what tests happen at commissioning, such as insulation resistance, string-level checks and a documented performance test, and whether you receive the reports.
Check 8: Confirm they manage approvals and grid connection
DISCOM approvals, metering, and any inspections required in your state can delay a project more than construction does. Ask who files the applications, who follows them up, and what happens to the schedule if approvals slip. For background on the rules, see our guide to the net metering policy.
Check 9: Check the operations and maintenance plan
A plant is judged by it runs for five year, not its commissioning day. Ask for the O&M scope: cleaning frequency, preventive maintenance, inverter and cable checks, remote monitoring, response times, spares and monthly performance reports. Make sure you get access to your plant’s generation data, whoever runs the O&M.
Red Flags in a Solar EPC Proposal
- A price far below other quotes with no BOM to explain the gap.
- Reluctance to name component makes or show certificates.
- “Guaranteed” generation with no measurement method or penalty.
- No site visit or roof assessment before quoting.
- Heavy advance payments not tied to project milestones.
- No O&M proposal, or no access to monitoring data.
- Subsidy assumptions. PM Surya Ghar is designed for residential households, so a commercial or industrial proposal should not depend on it.
How to Compare Solar EPC Quotations Like for Like
Put every bid into one sheet. If a bidder leaves a field blank, treat it as a question, not a saving.
| Item to compare | Bidder A | Bidder B | Bidder C |
|---|---|---|---|
| System size (kWp DC / kW AC) | |||
| Module make, model, Type, ALMM status | |||
| Inverter make, model, warranty | |||
| Mounting structure material and spec, strength report | |||
| Estimated annual generation and assumptions | |||
| Performance guarantee (metric, period, penalty) | |||
| Approvals and net-metering scope | |||
| O&M scope and duration | |||
| Schedule and payment milestones | |||
| Total price and what it excludes |
Then score each bidder. The weights below are a starting point; adjust them to your priorities.
| Criterion | Suggested weight |
|---|---|
| Engineering and yield assumptions | 20 |
| Component quality and compliance | 20 |
| Track record and references | 15 |
| Warranties and performance guarantee | 15 |
| Execution capability and safety | 10 |
| O&M and monitoring | 10 |
| Commercial terms and price | 10 |
Price gets only a tenth of the weight on purpose. Compare it after the technical comparison, not before.
Contract Clauses to Lock Down
- The BOM as an annexure, with a clause that substitutions need your written approval and must be equal or better.
- Delivery and commissioning dates, with delay damages.
- Payments linked to verified milestones.
- The performance guarantee: metric, measurement method, test period and remedy.
- Warranty handover, including documents and claim procedure.
- Acceptance tests and the documents you receive at handover.
- O&M scope, response times and data access.
- A defect liability period after commissioning.
Have your legal and finance teams review the contract. Tax treatment of the investment is a separate question for your chartered accountant.
How HCK Solar Approaches EPC Projects
HCK Solar Energy Limited is a vendor-neutral Solar EPC company serving commercial and industrial customers across India. We cover solar power plant design, engineering, installation, commissioning and relevant operations and maintenance support, for rooftop, ground-mounted and floating solar. If storage is part of your plan, see our BESS solutions.
If you are already collecting quotes, you can use the checklist above on ours too. Before you decide, read our guide on how to plan your rooftop solar power plant and what to not overlook while investing in a solar power plant.
Conclusion: Choose on Evidence, Not on Price Per kWp
Knowing how to choose a solar EPC company comes down to evidence. Ask for the engineering assumptions, the named BOM, the ALMM proof, the performance guarantee and the O&M plan. Put every bid in the same format, score it, and only then look at price.
Your next step: collect your last twelve months of bills and a roof layout, share them with two or three EPC companies, and run the comparison table above. To discuss your plant, contact the HCK Solar team.
FAQs (Exactly Five)
Q1. Do I need ALMM-listed modules for my factory’s rooftop plant?
Approved ALMM list applies to net-metering and open-access renewable energy projects, among others. For those, modules must be from List-I and, from 1 June 2026, use cells from List-II unless the project is sure to be commissioned by 31st December 2026. Rules depend on your connection route and can change, so ask your EPC to confirm applicability in writing.
Q2. How many EPC quotations should I compare?
Three is a practical minimum and four is plenty. More bids add noise unless every bidder gets the same inputs. Send identical bills, load data and roof details, and require the same BOM format so the comparison is like for like.
Q3. Can the EPC change component brands after I sign?
Only if the contract allows it. Attach the BOM as an annexure and require written approval for any substitution, which must be equal or better and still meet compliance requirements such as ALMM.
Q4. Who is responsible if the plant generates less than promised?
The EPC, if the contract contains a performance guarantee. Component makers cover their products under warranty, but the system-level result is the EPC’s responsibility. Make sure the guarantee defines the metric, the measurement method and the remedy.
Q5. Should I choose an EPC company that also provides O&M?
Often it is simpler, because one party then answers for both construction quality and long-term performance. Either way, check the O&M scope, response times, reporting and your access to monitoring data, and compare the O&M price separately from the build price.
Implementation: add these in Rank Math’s FAQ block. Google restricts FAQ rich results to a limited set of sites, so treat the markup as structure for readers and answer engines, not a promise of a rich result.
