This page walks through the usual milestones in a solar, wind or hybrid EPC contract and the securities that sit beside them. It describes common structures, not a model contract, and every project’s terms are negotiated.
Why milestones, not monthly valuations
Some construction contracts pay monthly against measured work. Renewable EPC contracts, particularly lender-financed ones, more often pay against defined milestones, because each milestone can be checked against a clear event: a signed notice, a delivery record or a test certificate. That makes it easier for the owner’s engineer and the lenders to confirm the work before money moves.
The usual sequence
| Milestone | Typical evidence | Paired security |
|---|---|---|
| Advance payment at notice to proceed | Signed notice to proceed | Advance payment guarantee |
| Major equipment ordered | Purchase orders and supplier confirmations | Often covered by the advance guarantee |
| Equipment delivered to site | Delivery notes and receiving inspections | Title and insurance in the owner’s favour |
| Construction progress stages | Owner’s engineer certificates | Performance security |
| Mechanical completion | Completion certificate and punch list | Performance security |
| Commercial operation or provisional acceptance | Test results and acceptance certificate | Retention starts to count down |
| Final acceptance | Defects period closed, performance proven | Retention released, securities returned |
Advance payment and its guarantee
An advance payment helps the contractor place orders for long-lead items such as modules, inverters, transformers or engines. In return, the owner usually receives an advance payment guarantee from a bank, which reduces as the advance is recovered from later invoices. Both sides should agree how the advance is recovered and how the guarantee steps down.
Equipment milestones and title
Paying for equipment before it is installed is common, but the owner needs protection: title passing on payment, insurance, and clear marking of equipment held off site. On hybrid projects with gas turbines or engines, equipment milestones are often the largest single payments, so the evidence required should be agreed in detail.
Retention and performance security
Retention is a share of each payment held back until a later milestone, usually provisional or final acceptance, as protection against defects. Many contracts let the contractor replace retention with a retention bond. Performance security, usually a bank guarantee, protects the owner if the contractor fails to perform. These securities interact with the performance guarantees and liquidated damages described on our performance guarantee page.
How lenders fit in
On project-financed plants, lenders release loan funds against the same milestones, after their independent engineer confirms the work. That means a milestone invoice is only as good as the evidence behind it. Aligning the EPC milestones with the loan drawdown schedule from the start avoids months of cash flow strain. Our pages on lender engineer reviews and IPP EPC contracts cover the lender side.
Hybrid projects add their own milestones
Where a solar or wind plant is built with batteries and thermal firming, the payment schedule often has separate milestone tracks for each technology, because they progress at different speeds. Solar modules may arrive months before gas engines or turbines, and the battery may be commissioned last. Separate tracks keep cash moving on the parts that are ready, while the final acceptance milestone stays tied to the hybrid plant working as one system under its controller. Owners should make sure the acceptance tests for each track are written before the contract is signed, so that a delay on one technology does not hold back payment for work that is complete and proven on another.
Currency is another point to settle early. Imported equipment is often priced in one currency and local works in another, so milestone amounts and any exchange rate mechanism should be stated clearly.
Where disputes start
Most payment disputes come from vague milestone definitions, evidence requirements that were never agreed, or delays caused by the owner’s own scope such as grid connection. Clear definitions, an agreed evidence list per milestone, and a fair mechanism for owner-caused delay prevent most of them.
EPC contracting you can bank on
USP&E delivers solar, hybrid and thermal power plants under EPC, EPCM and O&M contracts, with ISO certified processes. We have delivered 150+ power projects in 45+ countries and contracted 25,000 MW since 2002, and we take Extreme Ownership of single-point delivery. See our EPC projects page.
Offices: Colorado Springs (1755 Telstar Dr, Suite 300), Knoxville (800 S Gay St, Suite 700), London (162-168 Regent Street), Johannesburg (22 Kildoon Rd, Bryanston), Cape Town (31 Brickfield Road, Woodstock) and China (No. 1 Ningzhou Road, Wuxi). Regions: USA | AFRICA | UK | UAE | CHINA. ISO 9001 and ISO 45001 certified.
EPC payment milestone FAQ
What are payment milestones in an EPC contract?
Defined events, such as notice to proceed, equipment delivery or completion, at which the contractor is entitled to invoice an agreed amount once the evidence is accepted.
What is an advance payment guarantee?
A bank guarantee given to the owner in return for an advance payment, reducing as the advance is recovered from later invoices.
What is retention in an EPC contract?
A share of each payment held back until a later acceptance milestone, protecting the owner against defects. It can often be replaced by a retention bond.
How do lenders affect EPC payments?
Lenders release funds against milestones after their independent engineer confirms the work, so EPC milestones should match the loan drawdown schedule.
Structuring a renewable or hybrid EPC?
We can discuss scope, milestones and securities for solar, hybrid and thermal projects.
Phone +27 10 822 2324, email info@uspeglobal.com with your site data, or go through the EPC team. Firming equipment for hybrid plants is in the USP&E inventory.