Battery storage projects: contracting for deliverability, resilience, and bankability

Battery storage has moved from a promising technology to essential infrastructure. As the volume of intermittent wind and solar generation on the grid increases, storage helps balance supply and demand, and supports energy security.

Brodies’ recent report, Evolution not revolution: Investing in the energy transition report, identifies storage as the lead UK renewables subsector for the next 24 months, with around three‑quarters of investors and developers planning to invest and many identifying it as their top priority.

Recent geopolitical instability has sharpened that focus. Volatile prices, tighter financing and supply chain pressures have made secure, flexible domestic capacity a strategic priority. For battery projects, that brings both opportunity and a tougher delivery environment. Investors and funders are now looking more closely at whether construction contracts deal realistically with delivery, interface and supply chain risk.

Why storage is booming: flexibility is the new value driver

Battery storage is attractive because it can provide low carbon flexibility. It allows electricity systems to respond to changing demand and changing renewable output and enables better utilisation of the renewables capacity on the grid. It also sits alongside the wider trend identified in the Brodies report: physical energy assets are increasingly being paired with digital control, smart infrastructure and data led operation.

Grid connection: still the critical path

Grid access remains the main bottleneck for battery storage deployment. The UK grid connection reform process is almost complete, with NESO and Ofgem issuing new connection offers focused on accelerating connections and prioritising deliverable projects. At the same time, the cost of delay has risen. As the consequences of failing to meet grid connection dates become more onerous, employers and funders are pushing harder on completion dates and liquidated damages, even where energisation depends on third parties. The practical message is that grid connection sits firmly on the critical path, while noting that grid connection dates can still slip. Storage projects need to be contracted on that basis.

Procurement model: EPC wrap, multi contracting and OEM led delivery

Battery storage is often described as “modular” and “quick to deploy”. That can be true for civils and installation, but it is not a reason to assume a low risk procurement. As the storage market matures, procurement strategy, interface management and risk allocation are increasingly important to bankability.

Broadly, we see three procurement patterns:

Single-point EPC wrap, where one contractor takes primary delivery responsibility (often preferred by funders where it is achievable).
Split contracting, for example separate civils, electrical, BESS supply and integration packages.
OEM led or integrator led supply, with a separate balance of plant contractor.

A full EPC wrap may give a funder a cleaner risk profile, but it may not be available, affordable or commercially realistic where equipment lead times are long or specialist suppliers hold the key technical risk. In a volatile supply chain environment, employers sometimes prefer split procurement to preserve flexibility on long lead equipment or pricing. That flexibility comes at a cost: multi package projects often run into disputes over commissioning, sequencing and systems integration unless interface obligations are clearly written down. In practice, the model we see most often is a BESS supply package paired with a separate balance of plant contract.

Where a project is split into packages, the interface matrix should be a contract document, not an informal project management guide. Responsibility for access, information release, energisation support and commissioning cooperation should be expressly allocated and enforceable.

Programme, completion and liquidated damages

Battery storage projects can run into trouble when 'completion' is tied to energisation or export rather than to the contractor's own deliverables. Grid connection dates in the UK are routinely revised, and where completion depends on them, contractors face liquidated damages for delays they did not cause and cannot remedy.

A better approach is to implement key project milestones, for example:

physical installation / mechanical completion;
ready for energisation;
energised and able to export;
performance and availability demonstrated over a test period.

Energisation and operational performance are commercially important, but that does not mean the contractor should carry all grid risk. Contracts should allocate responsibility for energisation dependencies, provide appropriate relief where third-party network actions cause delay, and link liquidated damages to milestones the contractor can actually control.

Supply chain and price risk

Supply chain resilience is a key issue for battery storage projects. Long lead equipment such as cells, inverters, transformers and switchgear may be sourced through international supply chains. In a volatile market, procurement delays can have a disproportionate impact on programme, financing costs and project economics.

As a result, contractual mechanisms such as long lead procurement schedules, early ordering protocols, vesting arrangements, off-site materials agreements and step-in rights are becoming increasingly common and are all practical tools.

The key point is that a fixed price contract is only as robust as the procurement behind it. Where risk allocation does not reflect market realities, the result is often either inflated pricing or disputes later in the project lifecycle.

OEM warranties

OEM (original equipment manufacturer) warranties are a defining feature of battery storage projects. Cell, inverter and BESS warranties underpin a project's revenue assumptions, and lenders rely on them as a form of credit support. Misalignment between these warranties and the EPC, supply or O&M contracts is one of the most common (and most expensive) sources of dispute later in the project's life.

Common misalignments include:

different warranty periods (the EPC or supply contract promises a longer warranty period than the OEM actually gives);
the OEM warranty depends on specific maintenance, operating or environmental conditions that are not passed through to the operator or services contractor;
the warranty requires approved installers, approved operators or OEM certified replacement parts, but the project documents allow a wider choice; and
notice periods, claim procedures, testing rules or data requirements under the OEM warranty are not mirrored in the project contracts.

The practical answer is to review OEM warranty terms before the EPC, supply and O&M documents are finalised. The project contracts should pass through the conditions needed to keep the warranty alive, require the contractor to avoid acts or omissions that would invalidate it, give the employer direct rights or assigned rights where needed, and make clear how OEM remedies interact with performance liquidated damages and defect remedies.

Grid interface and commissioning: core workstream

Commissioning a battery project is particularly sensitive to grid side requirements. A system can be physically complete but still unable to earn revenue if energisation, export, grid compliance or control system integration is incomplete. That makes grid readiness a delivery issue, not only a regulatory issue.

For contracts, that means:

defining responsibility for grid compliance submissions and technical evidence;
making cooperation and interface support express obligations;
aligning commissioning obligations with DNO or transmission owner processes and realistic outage windows;
including a clear relief regime where third party grid actions cause delay.

Conclusion: bankability depends on deliverability

The central message of Brodies’ report is that the energy transition is evolutionary, not revolutionary. Battery storage fits that message. It is not a standalone answer to the energy transition, but it is a key part of making a low carbon electricity system dependable.

For developers, investors and contractors (and their lawyers), the task is to make sure the contract structure reflects the realities of delivery. Grid dependencies, supply chain exposure, OEM warranty conditions and long term performance obligations all need to be recognised and allocated to the party best placed to manage them.

In the current market, that means a bankable contract will usually need:

milestones that separate physical completion from energisation, with liquidated damages linked to controllable deliverables;
procurement structures that match interface complexity and funder requirements;
clear long‑lead and supply chain mechanisms, including vesting and tightly framed price risk provisions;
performance, degradation and warranty regimes that work together and preserve OEM warranty cover.

Battery storage is accelerating as an asset class, but it remains a delivery challenge as much as a technology opportunity.

The successful projects will not be determined by technology or capital alone. They will also depend on clear, proportionate and commercially realistic contracts that support delivery, protect performance and provide a bankable mechanism to achieve commercial operations.