When you are designing a solar project, whether a rooftop array at your factory, a 1–5 MW ground-mounted system, or a utility-scale park, you will encounter one term: EPC. The right EPC partner determines whether a project is delivered on time, within budget, and to expected performance levels.
This guide explains what a solar EPC company does, the EPC process, key responsibilities, associated risks and how to select a qualified EPC partner based on execution capability and contractual accountability.
What is a Solar EPC Company?
A solar EPC company provides a turnkey solar system: Engineering (design and planning), Procurement (sourcing equipment and materials), and Construction (installation, testing, and commissioning).
An EPC contractor delivers a solar project from concept through commercial deployment. Under an EPC contract, the EPC is contractually accountable for delivery timelines and agreed performance standards.
Why does the EPC matter?
Selecting the right EPC partner is often more critical than choosing a specific module brand. The EPC is responsible for site risk management, supplier coordination, permitting and interconnection, and, finally, meeting milestones and performance commitments.
An effective EPC combines engineering expertise, supplier control, disciplined site execution, and rigorous project management.
The Three Pillars of EPC: Engineering, Procurement, Construction
Engineering: Design and Due Diligence
Engineering defines project feasibility, safety, and long-term performance. Engineering involves site surveys, structural and geotechnical checks, layout and electrical single-line diagrams, yield modelling, and protection and earthing design.
Engineers size the overall system, including panels and inverters. Detailed engineering reduces construction risk, minimises redesigns, and prevents schedule overruns.
Procurement: Equipment Selection and Timely Supply
Procurement covers equipment selection, supplier qualification, compliance verification, and logistics coordination. It includes sourcing modules and inverters, verifying suppliers through IEC, UL, and PVEL testing, contracting supply agreements, logistics, and DCR, ALMM, and other applicable local compliance requirements.
Strong EPCs maintain qualified supplier networks and enforce strict procurement discipline.
Construction: Safe, Quality Installation and Commissioning
Construction entails civil works, the erection of structures, electrical connections, transformers, HT/LT systems, testing, and commissioning to achieve COD (Commercial Operation Date).
The EPC manages site teams, safety compliance, inspections, and final handover. In larger projects, construction schedules and sequencing directly determine cost control and schedule adherence.
Typical Roles & Responsibilities of a Solar EPC Company
In standard EPC contracts, the EPC is responsible for:
- Project management and scheduling: Project milestones, resource planning, and reporting.
- Permitting & interconnection: DISCOM and grid approval applications, including inspections and documentation.
- Design & engineering: Electrical and civil drawings, protection set-ups, and energy yield modelling.
- Procurement & quality control: Supplier evaluation, factory acceptance tests (FAT), delivery monitoring.
- Construction & safety management: Site supervision, civil works, mechanical mounting, and electrical integration.
- Testing & commissioning: IV curve testing, earthing tests, inspection, and performance acceptance testing.
- Documentation & handover: Operation manuals, warranty documents, and performance guarantees.
- Initial O&M and training: Short-term maintenance and training the owner’s team on system monitoring.
EPC contracts often include insurance filings, subcontractor coordination, and claims management.
The EPC Process – Step-by-Step (from RFQ to COD)
Below is a typical execution sequence and delivery workflow:
- RFQ/RFP & vendor selection: At this stage, the project owner defines the technical scope and receives detailed commercial and technical bids from EPC contractors.
- Site survey & feasibility – Topography, structural check, geotech if required.
- Preliminary design & layout – Energy yield model and preliminary SLD (single line diagram).
- Procurement & supply chain – Long-lead orders; FATs and quality checks on vendors.
- Civil and mechanical works – Foundations, cable trenches, mounting assembly.
- Electrical works & grid integration – Inverters, combiner boxes, switchgear, protections.
- Testing & commissioning – IV curves, EL imaging, insulation tests, performance ratio measurement.
- DISCOM inspection & COD – Meter commissioning, safety checks, and commercial operation.
- Handover & warranty registration – Documentation and monitoring handover; start of defects liability / DNP (defect notification period).
Smaller projects (such as a rooftop installation) can be completed within a few weeks; a few MW ground-mount project typically takes several months; utility projects can take half a year to a year or more, depending on permitting and grid connection.
For planning purposes, a 6–12 week cycle can be used for small projects, whereas larger utility projects may require more detailed schedule planning and delivery.
Contract models: EPC vs EPCM vs Others
Understanding contract models helps with risk allocation:
- EPC (turnkey): The EPC has total responsibility for delivery, schedule, and cost. The client pays a premium and receives guarantees; delays and defects are compensated.
- EPCM (Engineering, Procurement, Construction Management): This involves the owner designing and managing; the owner buys significant equipment. This type of model provides the owner with greater control. Under EPCM, the owner retains procurement responsibility while the contractor provides engineering and construction management.
- RESCO / PPA / BOOT: In the case of zero-capex projects, the asset is owned and operated by an operator (usually a specialised EPC + O&M provider), and sold to the end user under a long-term PPA. This structure shifts both performance and financing risk away from the end user.
Select the contract model based on your risk appetite, control requirements, and financing structure.
About EPCs’ Price – Common Cost Drivers
EPC quotes usually fall within these ranges. These percentages vary by market conditions and project scale.
| Cost Component | Typical Share | Key Influences |
| Solar Modules | 40–50% | Technology (TOPCon/HJT vs PERC), DCR compliance, import duties |
| Land Acquisition/Civil Works | 15–20% | Site terrain, soil testing, foundation type (ground vs rooftop) |
| Inverters & BOS | 15–20% | String vs central inverters, monitoring systems, cabling |
| Engineering/Installation | 10–15% | Labor rates, structural reinforcements, and commissioning |
| Grid Connectivity | 5–10% | Transformer costs, transmission line distance, and approvals |
Large projects benefit from procurement scale and lower per-MW overhead. Small rooftop projects have higher relative soft costs.
Quality Control, Standards & Testing You Should Focus on
Quality matters. Ask your EPC for:
- Module & inverter certifications (IEC 61215, IEC 61730, UL, where applicable).
- Third-party test reports (PVEL, Fraunhofer, UL), if available.
- Factory Acceptance Tests (FAT) and site acceptance testing (IV curves, insulation resistance).
- Performance Ratio (PR) guarantees and a detailed acceptance methodology.
An advanced EPC will maintain documented QA/QC processes and supply traceability for module batches and inverter serials.
KPIs & Warranties – What to Track After Handover
Key performance indicators to track:
- Performance Ratio (PR%) vs modeled yield
- Availability / Uptime (targeting > 98–99% for commercial assets)
- Time to repair (TTR) and ticket resolution times
- Energy yield vs baseline model (monthly & annual)
Warranties to expect:
- Module product warranty (10–15 years typical) and performance warranty (≥80–85% guaranteed output at year 25).
- Inverter warranty (5–10 years, sometimes extended).
- EPC defects liability / DNP period (commonly 12–24 months).
Common EPC Risks – and How Contracts Mitigate Them
Risks include supply chain delays, design defects, soil conditions, underground utilities (such as sewers and cables), permitting delays, and grid interconnection problems. Well-structured contracts include:
- Milestone payments tied to deliverables
- Performance guarantees (PG) and liquidated damages for delay
- Escrow arrangements or retention money to ensure defect remediation
- Clear acceptance tests and dispute resolution clauses
Negotiating these clauses carefully protects both parties and aligns incentives.
How to Choose the Right EPC: Practical Checklist
Selecting the right solar EPC partner is one of the most critical decisions in a solar project. Beyond pricing, you need confidence that the EPC can deliver safely, on time, and to performance expectations. Below is a practical checklist explaining what to ask for and why each point matters.
- Portfolio and references of similar projects
Request references from completed projects similar in scale and technology to yours. Direct reference checks confirm execution quality, schedule discipline, and post-commissioning support.
- Bankability evidence
The audited financial reports or parent-company guarantees demonstrate the EPC’s capacity to absorb risks and warranties throughout the project’s life cycle.
- Detailed bill of materials (BOM)
The exact module models, inverter specifications, mounting systems, and electrical components must be listed on a transparent BOM. Test certificates and datasheets ensure that they meet the quality standards and are not substituted during execution.
- Project schedule and resource plan
Ask for the realistic construction schedule and information on the site workforce, equipment, and subcontractors. This confirms the EPC’s operational capacity to deliver without excessive subcontracting risk.
- Insurance and safety records
Both parties are safeguarded by proper insurance cover: workmen’s compensation, third-party liability, and project insurance. A good safety record will indicate effective site management and reduce the risk of accidents and delays.
- Performance guarantees and defect liability terms
Accountability is demonstrated by clear performance guarantees to (minimum Performance Ratio or availability). Defect liability clauses protect the project owner by obligating the EPC to rectify defects after commissioning.
- Sample contract with LDs and acceptance criteria
Looking at one EPC contract sample will give you an idea of how delays, underperformance, and change orders are addressed. Liquidated damages (LDs), definition of acceptance tests, and performance guarantee (PG) protect your commercial interests.
- Local permitting and utility experience
An EPC knowledgeable about the relevant local regulations, DISCOM procedures, and grid interconnection requirements will navigate these factors more quickly, preventing costly compliance mistakes. Local experience usually makes commissioning easier.
- Operation & Maintenance (O&M) capability
Standard EPC contracts exclude long-term O&M unless it is explicitly included as a separate scope. However, the EPC must provide credible maintenance. The availability of spare parts and response time are very important for minimizing post-commissioning downtime.
- Transparency on subcontracting
Clarify which activities the EPC performs directly and which are subcontracted. Solid accountability eliminates coordination gaps and ensures a uniform quality of civil, mechanical, and electrical works.
- Live site walkthrough
A site visit to either an active or completed project can enable you to see workmanship, safety measures, and site arrangement firsthand. A site walkthrough may reveal more of the EPC’s capabilities than a presentation or a brochure.
The checklist used to assess the EPCs will help you minimize risk, enhance project performance, and ensure the sustainability of your solar investment.
Post-commissioning – Handover and O&M
The EPC delivers documentation, including as-built drawings, test reports, and warranties, and provides access to monitoring after COD.
Most EPCs provide initial O&M packages. Long-term performance depends on defined responsibility for monitoring, preventive maintenance, and spare parts management. The long-term value of the project depends heavily on sustained O&M performance.
Conclusion
Execution quality determines project performance as much as technology selection. A reliable solar EPC partner is critical for delivering projects on time, within budget, and to expected performance levels. The right EPC partner combines sound engineering, know-how, rigorously practiced procurement procedures, and efficient construction management to deliver a project that will perform throughout its life cycle.
As a project owner, it is essential to have clear technical and commercial goals, conduct a comprehensive assessment of EPC credentials, and ensure that risks are distributed fairly through well-organized contracts. When technical scope, contracts, and execution planning are aligned, delivery timelines shorten, and performance risks decline.
Finally, a competent EPC partner reduces execution risk, protects capital investment, and accelerates commercial operation.
Frequently Asked Questions
What does EPC stand for in solar projects?
EPC stands for Engineering, Procurement, and Construction. An EPC company designs the project, procures all equipment, builds the plant, and commissions it for operation under a single contract.
What is the difference between a solar EPC and EPCM?
In EPC, the contractor assumes responsibility for cost, schedule, and delivery. In EPCM, the contractor manages execution while the project owner retains procurement and financial risk.
Does a solar EPC company provide solar panels and inverters?
Yes. EPC companies procure modules, inverters, mounting structures, electrical equipment, and balance-of-system components as part of the contract, as specified in the approved bill of materials.
Who is responsible for government approvals and grid connectivity?
EPC companies typically manage permits, utility approvals, and grid interconnection processes. These responsibilities must be clearly defined in the contract to avoid execution delays.
How long does a solar EPC project take to complete?
Project timelines depend on project size and complexity.
- Small C&I projects / residential: 6–12 weeks.
- Medium business ventures: 3–6 months.
- Utility-scale plants: 6–18 months.
The most time-consuming aspects are grid approvals and permitting.
Is O&M included in a solar EPC contract?
Most EPC contracts cover construction and commissioning only. O&M is usually offered as a separate, optional service and should be explicitly defined if required.
Is a turnkey EPC model better than managing multiple vendors?
For most owners, turnkey EPC simplifies execution by assigning single-point responsibility. Managing multiple vendors requires strong technical coordination and increases execution risk.
