PPA Mechanics

The EPC Contractor in a PPA Structure

EPC stands for Engineering, Procurement and Construction. In a PPA, the SPV that owns the system contracts a third-party EPC to build it. The EPC's quality is your quality.

Who is the EPC contractor?

EPC stands for Engineering, Procurement and Construction. They're the firm that physically designs, sources components for, and installs your solar system. Under a PPA, the EPC contracts with the SPV that owns the system, not with you — but their work product sits on your roof for 25 years.

Why their quality matters to you

A cheap EPC means cheaper system, which means lower tariff in year 1. But poor workmanship — leaky penetrations, badly-spec'd inverters, incorrect string sizing — costs you later via roof damage, lost generation, and disputes over performance guarantees.

What to ask about the EPC before signing

• MCS certification (mandatory for SEG and for most commercial schemes).
• NICEIC or equivalent electrical accreditation.
• Recent reference installations of comparable size — request 3 within last 24 months.
• Performance ratio achieved on previous installs (target 78%+).
• Insurance — public liability £10m+, professional indemnity £5m+.
• Roof penetration warranty (separate from panel warranty).

EPC vs O&M — different contracts

EPC builds the system; O&M operates and maintains it. The same firm may do both, or they may be separate. Either way, both must be bonded into the PPA structure so that EPC defects don't end up as your problem.