Turnkey vs split-package EPC: choosing a contracting model

When an owner contracts for a solar plant or wind farm, one of the first decisions is how to divide the work. Should one contractor deliver everything under a single turnkey contract? Or should the owner split the work into separate packages — equipment supply, civil works, electrical works — and manage the interfaces itself? Each model has real advantages and real risks.

The models

Full turnkey EPC

One contractor is responsible for engineering, procurement and construction of the complete plant, handing it over ready to operate.

Split package

The owner contracts separately for major packages, for example:

• Module or turbine supply
• Inverter or electrical equipment supply
• Civil and structural works
• Electrical installation
• Substation and evacuation

Balance of plant (BoP)

A middle route: the owner buys the main equipment (modules, inverters or turbines) directly, and one contractor does everything else.

Comparing the models

Turnkey: pros and cons

Advantages:

• One contract, one counterparty
• Contractor bears interface risk between design, supply and construction
• Whole-plant performance guarantee
• Simpler for lenders

Disadvantages:

• Price includes the contractor's risk premium
• Less owner control over equipment choice
• Owner relies heavily on one contractor's capability

Split package: pros and cons

Advantages:

• Potentially lower total cost
• Owner chooses each supplier and contractor
• Direct relationships with equipment manufacturers
• Flexibility to use specialists for each package

Disadvantages:

• Owner bears interface risk — gaps, overlaps and delays between packages
• Performance guarantees split across contracts, making claims harder
• Higher owner management effort
• Disputes over who caused a problem

Balance of plant: the middle ground

Owners who want control over major equipment — perhaps for procurement requirements, bulk purchasing or manufacturer relationships — but don't want to manage many construction interfaces often choose BoP. The interface between owner-supplied equipment and the BoP contractor (delivery, storage, installation responsibility, damage) must be clearly defined.

Factors in the decision

Owner capability

Does the owner have an experienced team to manage multiple contracts and interfaces? Without it, split packages are risky.

Project size

Larger projects may justify the effort of split packages for cost savings; smaller ones often favour turnkey for simplicity.

Lender requirements

Lenders may require a single point of responsibility or strong interface management.

Equipment procurement

Procurement requirements or owner supply agreements may favour BoP. Check current requirements applicable to equipment sourcing.

Schedule pressure

Turnkey can simplify schedule management; split packages need tight coordination.

Managing interfaces

Whatever the model, interfaces must be explicit:

• Scope matrix listing every item and its responsible party
• Interface agreements or coordination clauses between contractors
• Single integrated schedule
• Clear handover points — when one package hands over to the next
• Owner's engineer coordinating technical interfaces

See how EPC partnerships work.

Common interface problems

• Equipment delivered late, delaying installation contractor
• Foundations not matching structure design
• Cable specifications mismatched between packages
• Damage to owner-supplied equipment — who pays?
• Testing responsibilities unclear

Questions to ask

• Do we have the team to manage multiple contracts?
• What will lenders require?
• How much might split packages save, after accounting for our management cost and risk?
• How will performance guarantees work across packages?
• Who will coordinate interfaces day to day?

Warranties across packages

Under turnkey, one contractor usually stands behind the whole plant during defect liability. Under split packages, each supplier's warranty covers only its own scope, and a fault at the boundary between two packages can leave each pointing at the other. Owners using split packages should plan how warranty claims will be investigated and who will diagnose root causes.

Common mistakes

• Choosing split packages to save cost without management capability
• Underestimating interface risks
• Fragmented performance guarantees with no whole-plant test
• No integrated schedule
• Unclear responsibility for owner-supplied equipment

Hybrid approaches on large programmes

Owners building several projects sometimes mix models: turnkey contracts for early projects while their team builds experience, then BoP or split packages for later ones. Framework agreements with equipment suppliers across a programme can also secure supply while leaving construction contracting flexible. Whatever the mix, carry lessons from each project into the next contract — especially about where interfaces caused trouble.

How we help

Through EPC partner coordination and project management, we help owners compare contracting models, prepare scope matrices and manage interfaces between packages on the owner's side. Construction is performed by independent contractors.