Concerns raised over lack of guidance on battery energy storage systems

CROSS-UK explores regulatory duty for BESS installations

A new technology needed for the green transition is being incorporated into the built environment at pace, without a full understanding of all the risks. This is the view of some safety engineers regarding battery energy storage systems (BESS).

BESS installations are becoming an increasingly common feature of modern buildings, but there is concern that standards and guidance are not keeping pacxe with their use.

The concern has been flagged by Collaborative Reporting for Safer Structures UK (CROSS-UK) is an initiative of the Institution of Structural Engineers (IStructE), Institution of Civil Engineers (ICE) and Institution of Fire Engineers.

CROSS-UK seeks to help professionals to make structures safer by publishing safety information based on the reports they receive and information in the public domain. The initiative shares information and concerns produced by reporters, sector experts whose anonymity is protected.

One such CROSS reporter has highlighted potential gaps in guidance for battery energy storage systems (BESS). The reporter concerned that traditional safety measures may not address the fire, explosion and operational risks involved. 

Reporter’s submission

The reporter believes that because Approved Document B has not yet caught up with the developments in recent years of BESS, certain parts of the industry may consider that, as guidance is absent, any solution is acceptable.

There is no robust, widely accepted industry guidance available apart from the latest PAS 63100:2024, Electrical installations - Protection against fire of battery energy storage systems for use in dwellings. 

Its development has been a welcome initiative, but in the view of the reporter, more might be needed to cater for the needs of the built environment.

The reporter is concerned that BESS may be incorporated in buildings (of all occupancies and sizes) following traditional safety solutions that may not be appropriate for all the hazards involved with battery energy storage systems. 

For example, in certain cases compartmentation may not be enough to keep a fire in the compartment of origin, explosion vents may be needed for structural stability and managing overpressures, and traditional forms and access arrangements for firefighting may be ineffective and/or hazardous for people and the environment.

This is typical of innovation risk. A new technology needed for the green transition is being incorporated into the built environment at pace, without a full understanding of all the risks and implications.

The underlying cause is cultural, which is twofold: government expecting industry to solve the issue, and industry being comprised of a critical mass of designers who are not stepping up to address their responsibilities under the UK regulatory framework, retaining past behaviours and expecting someone else, or guidance, to solve everything.

While the improvement of statutory guidance, generation of industry guides, and further research has led to improvements on other innovation risks, such as those connected to cladding, mass timber, and to a degree, photovoltaic (PV) panels, in the reporter’s view the risks connected to BESS have not been picked up as a similar issue worthy of urgent attention.

The reporter suggests that the wider industry, organisations who are creating the hazard, and government departments should develop the knowledge and supporting guidance for safe implementation of BESS.

They state that, currently, there is a Bill being prepared that will make the fire and rescue services a statutory consultee on any BESS scheme. This is a positive step, in the reporter’s opinion, but they are not sure if the Bill will improve the interface with the built environment. The reporter also believes that a regulatory framework already exists to handle such instances (for example, The Dangerous Substances and Explosive Atmospheres Regulations 2002), however, without any guidance specific to BESS. 
 
The reporter draws attention to the following sources:

• Battery Energy Storage Systems (Fire Safety) Bill - Parliamentary Bills - UK Parliament

• Grid-scale battery energy storage systems - HSE

• The Dangerous Substances and Explosive Atmospheres Regulations 2002 - HSE

Expert panel comments

The reporter’s concerns were looked at by a CROSS expert panel, which notes that the use of battery energy storage systems (BESS) is expanding rapidly in the built environment, but current statutory and industry guidance has not kept pace.

Approved Document B does not specifically address BESS, and this absence of guidance may lead some to assume that any solution is acceptable. The Panel stresses that the functional requirements of the Building Regulations remain applicable regardless of gaps in statutory guidance.

Panel members acknowledge that new guidance is emerging, such as PAS 63100:2024 as mentioned by the reporter, and that a dedicated Bill is in progress which will make fire and rescue services statutory consultees for BESS schemes. While agreeing with the reporter that this is a positive step, the panel highlights that fire and rescue services are not design approval bodies. Their statutory role is consultation, and they may not always hold the specialist competencies required to assess such proposals. Responsibility for compliance rests with designers, contractors, and regulators.

The panel considers that BESS introduce risks that are not adequately addressed by traditional fire safety solutions. Issues such as compartmentation, explosion venting, firefighting access, and environmental impacts may require new approaches. This represents a broader challenge of integrating innovative technologies into buildings while ensuring compliance with functional requirements.

The expert panel also highlights that the role of the fire and rescue services in the proposed Bill is not for them to 'validate' or 'approve' a proposed design; that is the responsibility of other duty holders. Rather, fire and rescue services will make comments where appropriate under access and facilities for fire and rescue, and emergency planning and response.

Overall, the panel agrees that there is a need for industry and government to accelerate the development of knowledge, standards, and supporting guidance for BESS. Lessons from previous innovation risks, such as combustible cladding, suggest that timely and proactive action is essential to avoid repeating past shortcomings. 

Key learning outcomes 

For designers and fire engineers:

• Do not assume that silence in statutory guidance implies acceptability. Ensure BESS installations meet the functional requirements of the Building Regulations through robust fire safety design
• Consider hazards specific to BESS, including potential explosion, fire spread, and challenges to firefighting operations, and incorporate appropriate protective measures.

For regulators and approval bodies: 
Recognise that emerging standards such as PAS 63100:2024 are a useful reference but are not yet comprehensive. Continue to require evidence that designs satisfy functional requirements.

For building owners and Responsible Persons: 

• Be aware that BESS pose unique hazards and ensure that competent professionals are engaged to assess and manage the fire and explosion hazards associated with these systems.

CROSS Report ID: 1478
Published: 20 October 2025 
Region: CROSS-UK