What is EPC in Solar Energy? A Complete Guide for B2B Companies

EPC stands for Engineering, Procurement, and Construction. It is the most widely used contract model for building large-scale solar power plants in India and globally. Under an EPC contract, a single contractor — the EPC contractor — is responsible for the complete delivery of a solar project: from technical design all the way through to commissioning a fully operational plant.

For B2B companies — whether you are a solar panel manufacturer, a mounting structure supplier, a cable vendor, or an inverter distributor — understanding how EPC contracts work is essential. EPC contractors are your primary customers in the B2B solar supply chain. They source equipment, manage civil works, and handle every phase of construction.

"In the Indian solar market, winning an EPC contract worth ₹100 Cr to ₹1,200 Cr is not uncommon. The supply chain behind each of those projects runs into dozens of B2B vendors."

The EPC model shifts project risk from the buyer (the awarding authority, such as NTPC or a state utility) to the EPC contractor. The buyer specifies the output — a functioning solar plant of a certain capacity — and the EPC contractor is accountable for delivering it, on time and within budget.

Every EPC contract — whether for a 1 MW rooftop system or a 600 MW utility-scale project — is structured around three core phases. Understanding each phase tells you exactly where your product or service fits in the supply chain.

Engineering phase in detail

Engineering is the foundation of the entire project. During this phase, the EPC contractor conducts site surveys, performs solar resource assessments, finalises the layout of panel arrays, and produces complete design documentation. For large projects (10 MW and above), this phase alone can take 3–6 months.

From a B2B vendor perspective, the engineering phase is when equipment specifications get locked in. If you are a solar panel manufacturer, your product must match the watt-peak (Wp), efficiency, and certification requirements defined during engineering. Vendors who engage EPC contractors during the engineering phase — offering technical specifications and samples early — win more procurement deals.

Procurement phase in detail

This is the highest-value phase for B2B suppliers. The EPC contractor issues purchase orders, negotiates prices, arranges logistics, and manages delivery schedules for every component the project needs. For a 100 MW solar plant, procurement typically spans 40–60 different product categories.

Construction phase in detail

During construction, the EPC contractor manages civil works (foundations, trenching, roads), mechanical installation (mounting structures, panel fixing), and electrical works (cabling, inverter connections, switchgear, grid interconnection). For utility-scale projects, construction can run concurrently across multiple zones on site, with hundreds of workers and subcontractors active at the same time.

For equipment vendors, construction is where after-sales support matters. Timely delivery, responsive technical support, and on-site assistance during commissioning directly influence whether you get repeat orders from the same EPC contractor.

Not all solar projects are structured as pure EPC contracts. In India, especially under government schemes like PM-KUSUM, alternative models are common. B2B vendors need to understand the differences because each model creates a different buying dynamic.

EPC contractors range from large public sector undertakings (PSUs) to mid-size private companies. Understanding which type of EPC contractor is most relevant to your product or service helps you target your B2B sales efforts more precisely.

PSU EPC contractors

Public sector companies like NTPC, BHEL, Bridge & Roof Company India, ONGC, and Coal India execute solar projects either for themselves or for other government bodies. They follow structured procurement processes, often through the GEM portal or CPPP, and require vendors to meet strict pre-qualification criteria.

Private EPC contractors

Private EPC contractors — which include companies like Kosol Energie, GHV India, Phaloudi Constructions, Avirat Energy, and dozens of regional players — are typically more agile in procurement. They often source equipment through competitive quotations and are more open to relationship-based vendor engagement.

Subcontract EPC (associate model)

In large projects, a primary contractor (like Bridge & Roof) awards a BOS subcontract to an associate firm (like Phaloudi Constructions or GHV India). For B2B vendors, this creates two levels of engagement opportunity: directly with the prime contractor and with the subcontractor.

In the Indian context, EPC contractors are awarded projects by awarding authorities — central PSUs, state utilities, government departments, and urban local bodies. Each buyer type has a different procurement process and creates different supply chain opportunities.

For B2B companies trying to enter or expand within the solar supply chain, understanding the full project lifecycle is critical. Here is how a typical solar EPC project unfolds from the awarding authority's first tender notice to the day the plant starts generating electricity.

Stage 1: Tender issuance

The awarding authority (for example, NTPC or a Nagarpalika) publishes a tender on the GEM portal, CPPP, or BidAssist. The tender document specifies the project capacity, location, contract period, technical requirements, and evaluation criteria. This is when early vendor intelligence is most valuable — knowing which EPC contractors are likely to bid tells you who to approach for supply inquiries.

Stage 2: Technical bid opening

Interested EPC contractors submit their technical bids. Awarding authorities evaluate technical qualifications — experience, financial strength, technical compliance — before opening financial bids. Vendors who have pre-qualified with shortlisted EPC bidders are best positioned to receive purchase orders.

Stage 3: Financial bid and award

After technical evaluation, financial bids are opened. The lowest technically-compliant bidder typically wins. The Award of Contract (AOC) is issued, and the EPC contract is signed. For B2B vendors, this is the trigger to follow up aggressively — the EPC contractor now has confirmed funding and will begin procurement planning immediately.

Stage 4: Procurement and mobilisation

The EPC contractor begins issuing RFQs (requests for quotation), purchase orders, and advance payments to vendors. Site mobilisation — establishing temporary offices, access roads, and storage yards — also begins in parallel.

Stage 5: Construction and installation

Civil works (foundations, cable trenching), mechanical installation (mounting structures, panel fixing), and electrical works (inverter connections, switchgear, transmission lines) proceed according to the construction schedule. Phased completion and progressive commissioning are common on projects above 50 MW.

Stage 6: Testing, commissioning and handover

The plant undergoes performance ratio testing, string-level electrical checks, and grid synchronisation before final handover. The EPC contractor's liability for defects (the defect liability period, or DLP) typically begins from commissioning.

A solar EPC project is only as good as the components that go into it. Below is a comprehensive overview of the materials typically procured in Indian utility-scale and rooftop solar EPC projects — and what specification standards apply.

Solar panels

The dominant specification in 2025 is Mono-PERC panels in the 550–575 Wp range for ground-mounted projects. Panels must comply with IEC 61215, IEC 61730, and — for government projects — must be on the ALMM (Approved List of Models and Manufacturers) maintained by the Ministry of New and Renewable Energy (MNRE). Bifacial panels are increasingly specified for open-land projects due to their higher yield.

Mounting structures

Hot-dip galvanised (HDG) steel mounting structures are the standard for ground-mounted solar in India, due to the combination of structural strength and corrosion resistance required over a 25-year project life. Fixed-tilt structures dominate on cost grounds, though single-axis trackers are specified for projects in high-irradiance zones like Rajasthan and Gujarat where the additional yield justifies the cost.

Inverters

String inverters are dominant for rooftop and small ground-mounted projects (up to 5 MW). Central inverters (500 kW to 3 MW units) remain common for utility-scale projects. Grid-tie inverters must comply with IEC 62109 and CEA grid connectivity standards. For PM-KUSUM projects, inverters must be ALMM-listed.

• ✓DC solar cables (flame-retardant, UV-resistant, TUV-certified)
• ✓AC armoured cables (for connection to grid evacuation point)
• ✓Array junction boxes (AJB) for string combiner functions
• ✓DC distribution boards (DCDB) and AC distribution boards (ACDB)
• ✓Earthing kits (copper bonded rods, conductors, exothermic welding kits)
• ✓Lightning arrestors (as per IS 3043 and IEC 62305)
• ✓Cable trays (hot-dip galvanised or stainless for outdoor runs)
• ✓RCC pedestal foundations (for mounting structure bases)
• ✓Module cleaning systems (manual or automated, depending on project size)
• ✓Remote Monitoring Systems (RMS) — mandatory for PM-KUSUM projects
• ✓Safety signages and PPE kits (as per MNRE and OHSAS requirements)

In India's solar market, O&M (Operation and Maintenance) is increasingly bundled into EPC contracts rather than being awarded separately. Understanding the O&M component helps B2B companies identify recurring revenue opportunities well beyond the initial equipment sale.

Types of O&M contracts

The most common O&M structures in Indian government solar projects are:

Comprehensive O&M (CAMC): The EPC contractor (or a specialist O&M firm) is responsible for all aspects of plant maintenance, including labour, consumables, and replacement of failed components. This is the standard for projects above 10 MW.

Annual Maintenance Contract (AMC): Labour is covered but spare parts are billed separately. More common for smaller rooftop projects.

Long-term O&M (25-year RESCO model): Under PM-KUSUM RESCO contracts, the developer is responsible for O&M for the full 25-year project life as part of the tariff agreement.

O&M durations in government contracts

Contract data from Gujarat shows that O&M periods bundled with EPC range from 1 year (for small rooftop projects) up to 7 years (ONGC floating solar at Hazira). The NTPC Kawas solar O&M contract covered operations for 2 years after commissioning.

The solar EPC market in India creates opportunities across a wide range of product and service categories. Here is how different B2B companies can position themselves within the EPC supply chain.

Understanding EPC is one thing. Converting that knowledge into orders is another. Here are the most effective approaches for B2B companies looking to grow their solar EPC business in India.

1. Track tender awards, not just tender notices

Most B2B vendors focus on active tenders, but the most valuable intelligence is in award data. When a contract is awarded, you know exactly who the EPC contractor is, what the project involves, where it is located, and how large it is. That is when to make contact — not months later when procurement is almost complete.

2. Use the GEM portal and BidAssist proactively

The Government e-Marketplace (GEM) and platforms like BidAssist publish award notifications with contractor names and contract values. Building a weekly review process for award data in your target states (Gujarat, Rajasthan, UP) gives you a consistent pipeline of warm leads.

3. Get ALMM-listed if you manufacture panels or inverters

For any government solar project above 10 kW, panels and inverters must come from ALMM-listed manufacturers. If you are not listed, you are ineligible regardless of price. Prioritise ALMM registration as a non-negotiable compliance step.

4. Offer technical support, not just price

EPC contractors — especially those executing complex projects under tight timelines — value vendors who provide technical datasheets, application engineers, and on-site commissioning support. Companies that reduce the EPC contractor's technical risk win repeat business even when their price is not the lowest.

5. Build relationships before projects are tendered

By the time a tender is published, the winning EPC contractor already has preferred vendors in mind. Engage EPC contractors 6–12 months before expected tenders with product demonstrations, site visits, and sample supplies. The relationship built before the project often determines who gets the purchase order.