Battery Energy Supply Agreement BESA

Why split contracting won

Owners used to buy the battery through the EPC as part of a wrapped price. Splitting the battery out into a BESA gets direct OEM pricing — no EPC markup on what is usually the single largest line item — and warranty privity: claims run straight from the project company to the manufacturer, instead of through an intermediary that may no longer exist when the defect surfaces.

The trade is interface risk. In a split structure, the gap between the BESA scope and the EPC balance-of-plant scope — who terminates which cable, who provides the crane, whose delay is whose — is the owner's problem. A wrapped EPC gave you one throat to choke; a BESA gives you two contracts and a seam. Managing that seam is the owner's job, usually via a division-of-responsibility matrix.

What it actually governs

Four things, typically: the technical specification the delivered system must meet; supply and delivery — manufacturing slots, shipping, delivery terms, title and risk transfer; testing and commissioning — factory acceptance tests, site tests, and a capacity demonstration before handover; and the warranty package. That last part is what distinguishes a BESA from a simple purchase order.

The OEM warrants workmanship for a defined period and guarantees initial performance — usable capacity at delivery and round-trip efficiency under a specified test procedure. Whether the PCS sits inside the BESA or with the EPC varies by project and by integrator; DC-block-only supply is common, full AC-block supply exists, and the answer changes who owns the DC/AC interface. Long-term performance coverage is usually a separate instrument — a capacity maintenance schedule or the LTSA — not the BESA itself.

Delivery, envelopes, and the money clauses

Delivery versus site readiness is the classic one. Batteries ship on the factory's schedule; sites slip on the EPC's — or on interconnection. If containers arrive to an unenergized site, someone must pay for storage and perform preservation: cells commonly need periodic recharge and temperature control while they wait, and getting this wrong can void the warranty before the system is ever installed. Well-drafted BESAs spell out who stores, who preserves, who pays, and whether the warranty period starts at delivery or at commissioning. Owners who skip that drafting find out during the delay.

The warranty itself is conditional on an operating envelope — annual throughput, temperature limits, state-of-charge window, C-rate — and dispatch outside it gives the OEM an exit. Read those conditions against your intended revenue stacking before you sign, not after.

Then the money clauses: liquidated damages for late delivery and for missed performance guarantees, both typically capped, and the caps are where the negotiation actually happens. Finally, augmentation: a BESA is the natural place to lock pricing options for future capacity additions, because the OEM you buy from today is the one whose chemistry you will want to match later.

What the lenders' counsel checks

For project finance, the BESA is a bankability document. Lenders' counsel checks whether the performance guarantees are measurable and enforceable, whether the delay liquidated damages are meaningful against the debt-service consequences of missing the commercial operation date, and whether the entity giving the warranty will still be solvent when a claim lands — parent guarantees from the OEM group are a common ask.

They also probe the seam: if the plant underperforms, can the owner prove whether the fault sits in the BESA scope or the EPC scope? A test regime that cleanly separates battery performance from balance-of-plant performance is worth more to bankability than any single warranty term. The honest answer is that no BESA fully closes the interface gap — lenders price what's left.