Solar EPC: scope of work and how to select a contractor
EPC services
EPC (Engineering – Procurement – Construction) is a contracting model in which a single contractor is responsible for design, equipment supply, construction and handover of a system that meets its performance targets. This guide describes each work package, the standard process and how to assess contractor capability.
In this guide
01
The E – P – C scope in a solar project
- Engineering: site survey, roof and mounting structural calculations, single-line design, string/inverter configuration, yield simulation, lightning protection, earthing and fire safety design.
- Procurement: sourcing modules, inverters, mounting systems, cables, switchboards and monitoring; verifying certification, warranties and delivery terms.
- Construction: installation, testing and commissioning, acceptance and energisation, with safety, schedule and as-built documentation management.
- Usually bundled: long-term O&M, remote monitoring, construction insurance and performance guarantees.
02
Standard delivery process
- Survey and collection of load data, site documentation and connection point details.
- Basic design, yield simulation and preliminary financial analysis to fix capacity.
- Detailed design, material approvals, permitting and the grid connection agreement.
- Construction against milestones, with quality control per work package and rooftop safety measures.
- Testing, trial operation, performance acceptance and handover with operating documentation.
- O&M: online monitoring, cleaning, preventive maintenance, performance reporting and fault response under an SLA.
03
How to assess contractor capability
- A verifiable track record of completed projects of comparable size and type.
- In-house engineering: PVsyst simulations, structural calculations and electrical design produced by the contractor itself.
- Supply chain and manufacturer relationships that secure long-term warranty and spare part support.
- Safety procedures for work on operating roofs, coordinated so production is not interrupted.
- Post-handover O&M capability: monitoring platform, fault response times and periodic performance reporting.
04
Common risks in EPC contracts
- Vaguely defined scope with unclear boundaries between contractor and owner for permitting, connection and roof refurbishment.
- Yield guarantees without defined metering conditions, reference irradiation data and correction methodology.
- No provisions for module degradation, equipment warranty and what happens if a manufacturer exits the market.
- No clear responsibility for roof leaks arising after installation.
05
Types of solar EPC projects
- Commercial and industrial rooftop: uses factory, warehouse and retail roofs, prioritising self-consumption.
- Ground-mounted: larger scale, requiring land and more complex planning and connection procedures.
- Floating PV: installed on reservoirs, requiring hydrological survey, float and anchoring design and specialised construction methods.
- Solar plus BESS: storage added to shift generation, shave peaks or support power purchase contracts.
Frequently asked questions
How is EPC different from buying equipment and hiring an installer?
Under EPC, one party is accountable for the whole outcome — design, equipment, construction and accepted performance. When packages are split, the owner carries the coordination risk and has no single party to hold responsible for underperformance.
How long does an industrial rooftop system take to build?
It depends on size, roof condition and connection procedures. On-site works for MW-scale systems typically take weeks to a few months, but the overall schedule is usually driven by permitting and the connection agreement.
Is O&M needed once the system runs stably?
Yes. Output degrades quietly through soiling, string faults, inverter fan failures or insulation issues. Online monitoring and preventive maintenance detect these early and protect the investment.
Can a rooftop EPC contractor deliver floating solar?
Floating PV requires distinct capability: water and hydrological survey, float and mooring design, on-water construction methods and specialised O&M. Ask the contractor to demonstrate experience or to partner with a specialist float technology provider.
Related guides
Solar knowledge
Commercial rooftop solar in Vietnam: rules and delivery
A complete guide to industrial rooftop solar in Vietnam: self-production and self-consumption rules under Decree 58/2025/ND-CP, sizing against the load curve, realistic yields and the EPC delivery process.
Investment analysis
Solar investment cost and how to calculate payback
The cost structure of a rooftop solar project, what moves the cost per kWp, and how to calculate payback and levelised cost of electricity (LCOE) from simulated yield and grid tariffs.
Energy storage
BESS for industrial users: applications and sizing
What BESS does in a factory: peak shaving, shifting solar generation, backup during outages and supporting power purchase contracts. How to size power and energy, choose cell technology and meet safety requirements.
Sources
- Ministry of Industry and Trade (moit.gov.vn)
- Vietnam Electricity (EVN)
- IEA – Solar PV
- Global Solar Atlas – World Bank Group
This guide compiles reference information from legal documents and official sources; it is not legal advice. Technical and financial ranges are industry reference values — project decisions require a site-specific survey.
Need a solar plan for your plant?
Orca Energy surveys the roof, analyses the load profile, simulates yield and builds the financial case for all three routes: self-investment, ESCO and renewable purchase through DPPA.
0867 831 368•solar@orcaenergy.vn
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