Lessons Learned from BESS Construction Projects

Building a battery energy storage system is nothing like constructing a solar farm. The equipment is more complex, the interfaces between contractors are more numerous, the contractual dependencies are tighter, and the margin for error is thinner. Get one piece wrong — a poorly scoped site acceptance test, an ambiguous handoff between EPC and commissioning teams, a supplier contract that doesn't account for real-world degradation curves — and you're looking at delays that cost millions and performance shortfalls that haunt the asset for its entire operating life.

That's exactly why the "Lessons Learned from BESS Construction Projects" panel at the Energy Storage Summit 2026 in London was one of the most practically valuable conversations of the event. Moderated by Andy Colthorpe of Energy-Storage.news, the session brought together Steven Xuereb (Executive Director, Kiwa), Kai-Philipp Kairies (CEO, ACCURE Battery Intelligence), and Gili Almagor (Director of Energy Storage, Nofar Energy) — three professionals who collectively represent the testing, analytics, and development sides of the industry. Their combined perspective revealed something the slide decks rarely show: how much can still go wrong, even on projects led by experienced teams.

The Complexity Problem Nobody Talks About Enough

There's a tendency in clean energy coverage to celebrate capacity milestones — gigawatts contracted, gigawatt-hours deployed, countries hitting storage targets. What gets less attention is the operational reality of actually building these systems at scale.

BESS construction sits at the intersection of electrical engineering, civil works, software integration, thermal management, and grid interconnection — often managed by different contractors who may have never worked together before. The interface risk between these parties is where projects quietly fall apart. A delay in transformer procurement cascades into an idle EPC crew. A commissioning protocol that wasn't aligned with the battery management system vendor produces data gaps that make the site acceptance test inconclusive. A site that passed factory acceptance testing ships with firmware that doesn't match the grid operator's requirements.

None of these are hypothetical scenarios. They're the kinds of issues practitioners like Xuereb, Kairies, and Almagor deal with directly — testing and validating systems, analyzing operational data to detect anomalies, and deploying storage at the project development level. The Energy Storage Summit gave them a platform to share what they've actually seen.

What the Experts Flagged

Site Acceptance Testing Is More Critical — and More Complicated — Than Developers Expect

Site acceptance testing (SAT) is supposed to be the moment a project proves it works. In practice, it's often the moment where the accumulated ambiguities of the construction process become impossible to ignore.

The panel discussion surfaced a recurring problem: SAT protocols that aren't properly defined upfront, leaving room for disputes between developers and suppliers about what "passing" actually means. Does the system need to demonstrate rated power for a specific duration? Under specific temperature conditions? With which state-of-charge starting point? These details matter enormously, and contracts that leave them vague create friction at exactly the moment when everyone wants to close out and move on.

Getting SAT right requires working backwards from the operational requirements of the asset — not just checking boxes the supplier proposed. Developers who let equipment vendors define the acceptance criteria are essentially letting the vendor grade their own exam.

Data Isn't Just for Operations — It Starts at Construction

Kai-Philipp Kairies' perspective from ACCURE Battery Intelligence brings a dimension that construction-focused discussions often skip: the data architecture decisions made during construction shape what's possible in operations. If the battery management system isn't logging the right parameters at the right resolution, operators will lack the baseline they need to diagnose degradation later.

This is an insider insight that doesn't get enough airtime. The construction phase is when you establish your performance baseline — and if that data is incomplete or inconsistent, you're flying blind for the life of the asset. Some developers are now requiring detailed data handover packages as part of project completion, treating the BMS data record as a deliverable alongside the physical infrastructure. That's the right instinct.

Supplier Contracts Need to Account for Real-World Conditions

The gap between what a battery cell delivers in a manufacturer's test environment and what it delivers under real operational conditions — variable temperature, partial cycling, frequency regulation duty cycles — is where a lot of commercial disappointment originates. Almagor's experience at Nofar Energy, a developer with projects across multiple markets, gives weight to the observation that supplier warranties and performance guarantees often don't adequately reflect the actual use case.

Battery storage challenges in this domain aren't purely technical — they're contractual and commercial. Developers who push for performance guarantees tied to specific duty cycles and degradation thresholds are better protected than those who accept generic warranties. The negotiation happens before financial close, and the leverage disappears once the contract is signed.

Navigating the Contractor Interface Problem

One of the panel's sharper observations concerned multi-contractor projects and the gaps that emerge between scopes of work. In a BESS project, you might have a civil contractor, an electrical contractor, a battery system supplier, a grid connection contractor, and a controls/SCADA integrator — all working under an EPC structure, or sometimes under separate direct contracts with the developer.

The danger isn't that any individual contractor performs poorly. It's that each one delivers their defined scope perfectly and the interfaces between scopes are still broken. Who owns the communication protocol between the battery management system and the SCADA? Who is responsible if the protection relay settings are incompatible with the inverter's response characteristics? These gaps are predictable, and they're preventable — but only if someone is explicitly responsible for managing them.

Infrastructure development at this scale requires a systems integration mindset, not just a project management one. The developers and EPCs that build this capability in-house — rather than assuming the equipment suppliers will sort it out — consistently deliver projects with fewer surprises at commissioning.

The Regulatory Dimension

BESS projects don't exist in isolation from grid operators and regulators. The panel touched on compliance requirements that vary significantly by market, adding complexity for developers like Nofar that operate across geographies. Grid code compliance, protection settings, reactive power capability, and response time requirements can differ enough between jurisdictions that a project design optimized for one market needs meaningful re-engineering for another.

This matters for infrastructure development strategy. Developers who treat grid compliance as a late-stage checkbox item consistently run into delays at the interconnection stage. The teams that front-load grid code analysis — before detailed engineering, not after — tend to have smoother paths to energization.

Where the Industry Goes From Here

The battery storage challenges discussed at Energy Storage Summit 2026 aren't exotic edge cases. They're the normal friction of a young industry building at unprecedented scale, with supply chains, contractor ecosystems, and regulatory frameworks that are still catching up.

What's changing is the knowledge base. Events like the Energy Storage Summit serve a function beyond networking — they accelerate the transfer of hard-won operational experience across the industry. A developer in Poland benefits from knowing what Nofar learned on a project in Israel. A testing firm in Germany can apply Kiwa's SAT methodology to projects it wouldn't have encountered otherwise. ACCURE's data analytics insights make degradation visible in ways that weren't commercially accessible even three years ago.

The projects being financed today will operate for 15 to 20 years. The decisions made during construction — about contracts, data architecture, contractor interfaces, and acceptance criteria — will determine whether those assets perform as modeled or underperform quietly and expensively. Getting those decisions right isn't a technical nicety. It's where the economics of the energy transition actually get resolved.

The industry is learning. The question is whether it's learning fast enough to match the pace of deployment.

Call to Action: For more insights and resources on BESS construction projects, visit InfraSale Marketplace.

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