EPC (Engineering, Procurement & Construction)

An EPC (Engineering, Procurement & Construction) company is responsible for designing, sourcing, and building a complete solar power project—from initial site surveys to full system commissioning. In the solar industry, EPCs manage the technical engineering, secure all equipment and materials, oversee construction, and ensure the project meets performance, safety, and compliance standards.

EPCs play a critical role across residential, commercial, industrial, and utility-scale solar development. They coordinate structural and electrical engineering, procurement logistics, installation labor, permitting, AHJ requirements, quality control, and final system activation. Because EPCs carry both construction risk and performance accountability, they are central to the success, safety, and long-term reliability of a solar project.

Solar design platforms such as Solar Designing and project planning workflows like Solar Project Planning Hub help EPCs accelerate layouts, optimize engineering, and reduce installation errors.

Key Takeaways

EPC (Engineering, Procurement & Construction) companies deliver complete solar projects from design through construction.
They manage engineering, equipment sourcing, installation, and commissioning.
EPC models vary: Full EPC, EPCM, turnkey EPC, and EPC + O&M.
EPC performance is measured by cost accuracy, schedule dependability, engineering quality, and system output.
EPC teams rely heavily on digital tools for design, modeling, and project management.

What Is an EPC in Solar?

An EPC is a specialized organization contracted to fully deliver a solar PV project—from concept to completion. EPCs handle:

Engineering (structural, electrical, and civil design)
Procurement (modules, inverters, racking, BOS materials)
Construction (installation, wiring, commissioning, testing)

They ensure the solar project is properly designed, permitted, built, inspected, and interconnected. EPCs act as the single point of responsibility, making them essential for developers, asset owners, and large-scale customers.

Related concepts include Permit Package, Inverter Sizing, and Mounting Structure.

How EPC Works

The EPC process generally follows a structured sequence:

1. Engineering (E)

EPCs develop detailed technical plans, including:

System layout
Structural and electrical drawings
Single-line diagrams
AHJ-compliant fire pathways
Interconnection studies
Wind & snow load evaluation
Shading and production modeling

Tools like Solar Designing and Shadow Analysis help EPCs ensure accurate and optimized design.

2. Procurement (P)

EPCs source all materials required for the project:

Solar modules
Inverters
Racking & mounting systems
BOS components (wiring, breakers, fuses, conduit)
Monitoring hardware
Transformers & switchgear (for larger projects)

Procurement impacts project budgets, timelines, warranties, and long-term system reliability.

3. Construction (C)

EPCs oversee on-site construction, including:

Preconstruction field assessment
Racking and structural installation
Module mounting
Wiring and conduit runs
Inverter installation
O&M pathway creation
Testing and commissioning
Grid interconnection

They ensure that construction meets both engineering specifications and local AHJ requirements.

Types / Variants of EPC Models

1. Full EPC

EPC owns engineering, procurement, and construction end-to-end.

Typical for utility-scale and commercial projects.

2. EPC + O&M

Some EPCs also offer long-term Operations & Maintenance services.

3. EPCM (Engineering, Procurement & Construction Management)

EPC manages the construction rather than performing it directly.

Common when developers want more control.

4. Design-Build EPC

The EPC performs both design and construction directly for maximum efficiency.

5. Turnkey EPC

EPC delivers a fully completed, operational solar plant ready for energy production.

How EPC Performance Is Measured

EPC performance is typically evaluated by:

1. Cost Accuracy

Variance between estimated vs. actual cost.

2. Timeline Reliability

Adherence to project schedules and milestone delivery.

3. Engineering Quality

Accuracy of layouts, shading models, and electrical drawings.

4. Procurement Efficiency

Lead-time management and supply chain coordination.

5. Construction Quality

Installation durability, code compliance, and safety performance.

6. System Performance

Post-commissioning energy output vs. expected yield.

See Performance Ratio.

Typical EPC Roles & Responsibilities

Engineering

SLDs, 3LDs
Structural load analysis
Module layout
Roof/ground mounting analysis
Interconnection application
AHJ & NEC compliance review

Procurement

Vendor management
Price negotiation
Logistics & delivery scheduling
Equipment testing
Material verification

Construction

Site preparation
Racking and module installation
Stringing & electrical work
Inverter and BOS installation
Quality & safety checks

Practical Guidance for EPC Teams

1. Use automated design tools

Speeds up engineering accuracy using tools like Solar Designing.

2. Standardize Bill of Materials (BOM)

Reduces procurement errors and improves cost predictability.

3. Integrate shading models early

Use Shadow Analysis to prevent underperforming arrays.

4. Maintain strong AHJ communication

Smooths permitting and inspection stages.

5. Plan construction sequencing

Reduces labor bottlenecks and improves safety outcomes.

6. Track project progress digitally

Tools like the Solar Project Planning Hub help manage milestones.

7. Use accurate AC/DC modeling

Ensure optimal inverter pairing and layout decisions—see Inverter Sizing.

Real-World Examples

1. Residential EPC Delivery

An EPC manages a 7 kW rooftop installation—from engineering the layout, sourcing materials, and installing the system to scheduling AHJ inspections and commissioning the system.

2. Commercial EPC Project

A 500 kW flat-roof solar system is delivered as a turnkey EPC project. The EPC handles structural analysis, module layout, walkway planning, procurement of ballasted racking, and all installation labor.

3. Utility-Scale EPC

A 50 MW solar farm is delivered by a full-service EPC responsible for civil engineering, pile driving, inverter station installation, tracker assembly, string wiring, SCADA integration, and grid interconnection.