The term Solar EPC appears throughout the US solar industry, in job postings, contract structures, and everyday industry conversation, but its exact meaning is often unclear to people entering the industry or working with solar companies for the first time. EPC stands for Engineering, Procurement, and Construction, and a Solar EPC is a company that handles all three functions for solar photovoltaic projects. This guide walks through what solar EPCs actually do, how they differ from other companies in the solar value chain, the types of solar EPCs operating in the US market, and where outsourced engineering fits into the EPC model.
What does Solar EPC mean?
Solar EPC stands for Solar Engineering, Procurement, and Construction. A solar EPC company takes end-to-end responsibility for delivering a solar photovoltaic project from design through construction and commissioning. The three functions are:
- Engineering: the technical design of the solar system, including site assessment, system sizing, equipment selection, structural analysis, electrical design, plan set preparation, PE stamping where required, permit applications, and utility interconnection engineering.
- Procurement: sourcing and purchasing all equipment and materials needed for the project, including modules, inverters, racking, wiring, disconnects, protective equipment, monitoring systems, battery storage where included, and all balance-of-system components.
- Construction: physical installation of the solar system, including racking installation, module installation, electrical work, inverter installation, interconnection with the electrical service, commissioning, testing, and handover to the customer.
A solar EPC delivers a turnkey project, meaning the customer receives a complete, operating solar system rather than having to coordinate multiple contractors.
How solar EPCs differ from other companies in the solar value chain
The US solar market has several distinct company types that are sometimes confused with EPCs:
Solar developers
Solar developers originate and own solar projects. They identify sites, secure land or roof leases, negotiate power purchase agreements, arrange project financing, and hold ownership through construction and often operation. Developers may hire an EPC to build the project, or they may have in-house EPC capability. Large solar developers often maintain both developer and EPC functions.
Solar installers
Solar installer is a broad term that overlaps significantly with EPC. In the residential and small commercial segment, installer is the more common term. Larger commercial and utility-scale projects more commonly use EPC. Functionally, a residential solar installer handles the same engineering, procurement, and construction scope as an EPC, just at smaller project scale.
Solar contractors
Solar contractor usually refers to a specialty subcontractor performing a specific scope within a larger project. Electrical contractors, roofing contractors, and racking installation subcontractors may all be called solar contractors. EPCs and larger installers often manage teams of solar contractors as subcontractors on projects.
Solar consultants and engineering firms
Solar consultants and dedicated solar engineering firms provide engineering services (design, plan sets, PE stamping, permit engineering) without handling procurement or construction. These firms serve as design partners to EPCs, developers, and installers who need engineering capacity beyond their in-house team. Outsourced solar design firms like RIH Engineering fall in this category.
Solar module manufacturers, inverter manufacturers, racking manufacturers
Manufacturers produce the equipment used in solar projects but do not typically install systems directly. EPCs and installers source equipment from manufacturers or through distributors.
Types of solar EPCs
Solar EPCs specialize by market segment:
Residential solar EPCs (usually called installers)
Residential solar installers focus on single-family and small multi-family rooftop projects, typically ranging from a few kW to 20 kW per project. Residential installer economics depend on high project volume, fast permit-to-PTO cycles, and efficient customer acquisition. Companies like Sunrun, Sunnova, and many regional installers serve this segment.
Commercial and industrial (C&I) solar EPCs
C&I solar EPCs focus on commercial rooftops, warehouses, distribution centers, parking canopies, and mid-sized ground-mount projects, typically ranging from 100 kW to several MW per project. C&I project economics involve more complex design, financing, and interconnection than residential, with longer project timelines and larger per-project revenue.
Community solar EPCs
Community solar EPCs focus on community solar garden projects, typically 1 MW to 5 MW per project, sited on commercial rooftops, brownfields, agricultural land, or dedicated parcels. Community solar EPCs combine C&I-scale engineering and construction with the additional program compliance, subscriber management coordination, and utility interconnection complexity specific to community solar.
Utility-scale solar EPCs
Utility-scale solar EPCs focus on solar farms of 5 MW and up, sometimes into the hundreds of MW. Utility-scale projects involve substantial civil engineering, complex interconnection studies, long lead times, and specialized construction management. Utility-scale EPCs like Blattner Energy, Rosendin Renewable Energy, and many others serve this segment.
Key services a solar EPC provides
The engineering scope alone within a solar EPC covers a wide range of services:
- Site assessment and feasibility analysis
- System sizing based on customer load profile and site constraints
- Production modeling using Helioscope, Aurora Solar, PVWatts, or PVsyst
- Shading analysis
- Equipment selection (modules, inverters, racking, storage, monitoring)
- String design and inverter loading calculations
- Structural analysis (roof loading, attachment design, ground-mount racking foundations)
- Electrical design (single-line diagrams, three-line diagrams, conductor sizing, protection coordination)
- Rapid shutdown design per NEC 690.12
- Battery storage design per NEC Article 706 and NFPA 855 (for storage-inclusive projects)
- Interconnection engineering coordinated with the specific utility
- Plan set preparation formatted for the specific AHJ and utility
- PE stamping (structural, electrical, or both depending on state and project)
- Permit application preparation and submission
- Permit revision cycle management
The procurement scope covers equipment sourcing, purchasing, logistics, and inventory management. The construction scope covers installation, commissioning, testing, and handover.
How solar EPCs are compensated
Solar EPC contract structures vary by market segment:
- Residential: typically fixed-price turnkey contracts based on system size, with pricing per watt or per kW installed
- C&I: often fixed-price turnkey contracts based on detailed scope, sometimes with adjustments for site conditions
- Utility-scale: various structures including fixed-price, cost-plus, engineering procurement and construction management (EPCM), and hybrid approaches
- Design-build contracts: EPC handles design and construction under one contract, offering the customer single-point accountability
Where outsourced engineering fits into the EPC model
Solar EPCs face a persistent capacity challenge: engineering demand fluctuates with pipeline, and hiring full-time engineers for peak demand leaves them under-utilized during slower periods. Outsourced engineering partners provide flexible capacity, allowing EPCs to scale design and permit engineering up and down with pipeline without carrying fixed overhead.
Outsourced solar engineering typically covers plan set preparation, PE stamping coordination, permit application preparation, structural analysis, single-line diagram preparation, Helioscope and Aurora modeling, and interconnection documentation. The EPC retains customer relationships, procurement, construction, and overall project management, using outsourced engineering as a specialized capacity extension.
RIH Engineering serves as an outsourced engineering partner to solar EPCs and installers across the US, delivering AHJ-ready plan sets, PE-stamped designs, and interconnection documentation formatted to each utility. If you want to talk through how outsourced engineering fits your EPC operations, get in touch.
Frequently asked questions
What does Solar EPC stand for?
Solar EPC stands for Solar Engineering, Procurement, and Construction. A solar EPC company takes end-to-end responsibility for delivering a solar photovoltaic project from design through construction and commissioning, handling engineering (technical design), procurement (equipment and materials sourcing), and construction (physical installation and commissioning).
What is the difference between a solar EPC and a solar developer?
A solar developer originates and owns solar projects (site identification, land/roof leases, power purchase agreements, financing). A solar EPC delivers the physical project (engineering, procurement, construction). Developers may hire EPCs to build their projects, or maintain in-house EPC capability. Many larger companies operate as both developer and EPC.
What is the difference between a solar EPC and a solar installer?
The terms overlap significantly. Solar installer is more common in residential and small commercial segments; solar EPC is more common in commercial and utility-scale segments. Functionally, both handle engineering, procurement, and construction. The distinction is primarily one of project scale and industry terminology convention, not fundamental scope of services.
What types of solar EPCs operate in the US market?
US solar EPCs specialize by market segment: residential installers (single-family and small multi-family, kW-scale), commercial and industrial (C&I) EPCs (100 kW to several MW), community solar EPCs (1 MW to 5 MW community gardens), and utility-scale EPCs (5 MW and up, sometimes hundreds of MW). Each segment has distinct engineering, financing, and construction patterns.
Can solar EPCs outsource their engineering work?
Yes. Many solar EPCs use outsourced engineering partners to handle plan set preparation, PE stamping coordination, permit application preparation, structural analysis, single-line diagrams, and interconnection documentation. This provides flexible engineering capacity that scales with pipeline demand without the fixed overhead of full-time engineering staff. The EPC retains customer relationships, procurement, construction, and overall project management.