Building bankable battery projects
Europe’s battery energy storage system (BESS) market is booming, but financing still hinges on one thing: bankability. This blog breaks down the key technical and commercial insights that matter most to lenders and investors evaluating today’s battery projects.
1. Why battery storage matters for the energy transition
Battery energy storage systems are increasingly central to Europe’s energy transition. End of 2025 the Joint Research Centre reports over 13.9 GW of operational electrochemical (BESS) projects with another 85 GW of additional expected projects (announced, permitted, in construction). This development is supported by ongoing global cost reductions, with a 31% reduction in 2025 as reported by Bloomberg NEF. What once bought 1 MWh of capacity in 2022 now buys three times as much by 2025. As variable renewable generation expands rapidly, power systems require fast-responding flexibility to maintain frequency stability, manage congestion, and balance supply and demand. BESS provides these services while also enabling energy shifting and more efficient utilization of existing grid infrastructure. In many European markets, BESS is now viewed as required system infrastructure rather than a niche merchant asset.
2. From merchant risk to bankable revenues
BESS deployment across Europe has expanded rapidly in recent years, driven initially by strong merchant revenue opportunities.
Early standalone projects typically relied on ancillary services and balancing markets. This phase enabled fast growth but also exposed projects to significant revenue uncertainty. However, ancillary service markets in many EU countries have since matured and become more competitive. This means energy storage systems are increasingly used on wholesale markets too, with uncertainty over the development of price spreads. As a result, energy storage is exposed to merchant risk which has implications on the financing of BESS projects.
This has led to increased demand for fixed or contracted revenue mechanisms, such as floor off-take agreements, fixed revenue (tolling) agreements, or hybrid structures, that can stabilize cash flow and support project debt. These structures reduce exposure to short-term market fluctuations and protect against downside risk, while reducing upside potential. Despite this demand, the supply of such fixed-revenue contracts remains limited. Offtakers and optimizers are cautious about locking in long-term fixed prices in a still evolving BESS market. This misalignment has created a gap: financiers seek contracted revenue for bankability, while many developers continue to rely on merchant optimization due to lack of contracting options.
For some countries this gap is partially bridged by the introduction or expansion of Capacity Mechanism (CM) schemes. BESS projects increasingly view these auctions as a complementary revenue stabilizer. CM contracts provide long-term, availability-based income that directly supports debt structuring when combined with merchant or semi-contracted revenue streams.
3. Trends for bankable BESS projects
Several recurring trends emerge that strongly influence bankability. These themes apply to both standalone and co-located battery projects and reflect a combination of market maturity, regulatory evolution, and technical integration challenges. Below, a short summary of some of these factors is provided.
3.1 Sizing duration
Ancillary service saturation is no longer just a commercial concern; it directly influences system design. Historically, one-hour BESS dominated because they were optimized for FCR participation. As these markets have become saturated, the industry is shifting toward longer-duration assets. In most European markets, two-hour systems are the standard, and in several markets, developers are moving towards four-hour configurations. Longer durations expand access to wholesale arbitrage, intraday and day-ahead trading, and diversified revenue stacking, reducing reliance on any single ancillary product. This evolution also affects capex allocation, degradation assumptions, and lender expectations.
3.2 Cost trends and technology evolution
Battery costs have declined significantly over the past decade, driven by scale, learning effects, competition and supply chain optimization. Lithium iron phosphate (LFP) chemistry has become dominant in Europe due to its safety profile, cycle life, and price level. From a bankability perspective, assumptions around degradation, usable capacity, efficiency, availability and warranty coverage are critical inputs to financial models.
Manufacturers have significantly improved battery durability. Earlier utility-scale systems were typically warranted for 6,000-8,000 cycles, limiting economic life for high-cycling applications. Today, suppliers routinely offer 10,000-12,000-cycle warranties depending on the use case. A major industry trend is the extension of guaranteed operating lifetime. Where systems previously carried 10–15-year performance guarantees, many now provide 15–25-year warranties. This shift is driven by improved cell chemistry stability, more sophisticated thermal management systems enabling tighter degradation control, larger operational track record reducing uncertainty and strong supplier competition, particularly in China, all leading to improved guarantees.
The market has shifted decisively from NMC to LFP for utility‑scale BESS, driven by LFP’s lower cost, stronger thermal stability, longer cycle life, and reduced exposure to volatile raw material prices. As a result, LFP has become the dominant chemistry for new projects, materially improving cost structures and project economics. At the same time, emerging chemistries such as sodium‑ion are gaining industry interest with the first utility-scale projects being announced. While they offer promising cost resilience and safety benefits, they currently lack the operational track record and production scale. This means that the lithium‑ion LFP solution remains the standard for investment‑grade utility‑scale projects.
3.3 Standardization of safety
Fire safety for utility-scale BESS has increasingly standardized around key norms. In most countries these norms, or part thereof, form the basis of fire safety requirements. However, country or project specific requirements remain a challenge to European-wide standardization of designs and technical solutions. In addition, to meet these requirements, large-scale fire propagation testing is becoming standard practice to validate real-world system behaviour and strengthen overall safety assurance.
3.4 Grid connection uncertainty
Grid connection certainty and technical limitations are important aspects in the bankability of BESS projects. A clear distinction must be made between firm and non-firm connections, as this determines the level of operational certainty the asset can deliver. Non-firm connections typically come with curtailment obligations, import limitations or other restrictions, directly affecting the system’s ability to generate contractual revenues or participate fully in wholesale or balancing markets. In addition, grid-related fees, including upfront connection costs and ongoing network tariffs, are being re-evaluated in various European countries, leading to uncertainty. In many markets these charges materially affect overall project economics, and matching technical restrictions with revenue forecasts is critical in de-risking projects.
3.5 Hybrid systems: Increasingly valuable, but more complex
Hybrid systems, typically combining BESS with solar or wind, are becoming more relevant across Europe, particularly in congested grids. Their appeal comes from several clear advantages. Hybridization helps mitigate grid congestion, reduce curtailment, and improve utilization of existing connection points. It also enables shared infrastructure and capex efficiencies, supports stronger revenue stacking, and creates more diversified revenue streams that financiers increasingly value. In heavily congested markets, hybrid configurations can assure grid access that would not be available for standalone BESS.
These benefits come with additional complexity. Hybrid systems limit operational freedom, create more challenging dispatch coordination requirements, and demand more sophisticated contractual structures. On the regulatory side, hybrid projects may also lead to additional risks, especially when renewable generation is subject to incentive schemes, as complexities such as specific metering requirements may apply.
Grid code compliance becomes more demanding as well, as a shared grid connection means the renewable asset and the BESS cannot export simultaneously without breaching connection limits. While energy arbitrage dispatch usually avoids conflicts through market signals, ancillary services such as FCR can create operational restrictions that must be technically coordinated. To ensure compliant operation, the integrated plant requires a power plant controller capable of enforcing export limits, managing curtailment, and setting clear priority between generation and BESS.
3.6 Policy and regulatory signals
Policy support for energy storage is improving across Europe, but harmonization remains limited. Policymakers increasingly acknowledge the role of storage in easing grid congestion, integrating renewables, and enhancing system stability. However, implementation varies significantly between countries. Key questions remain unresolved, including how to ensure batteries operate in a grid friendly manner without jeopardizing the main business case drivers, and how to design incentives that reward genuine system benefits.