New Wiring Regulations for Battery Storage: What Social Housing Landlords Need to Know

What Changed in April 2026

On 15 April 2026, the Institution of Engineering and Technology and the British Standards Institution jointly published Amendment 4 to the IET Wiring Regulations: BS 7671:2018+A4:2026. This is a substantial revision to the 18th Edition and is already in use. The previous edition is formally withdrawn on 15 October 2026.

The headline change for retrofit programmes is the introduction of an entirely new Chapter 57: the first time the wiring regulations have contained dedicated provisions for stationary battery storage systems. Until now, installers worked from a patchwork of manufacturer guidance, MCS standards, and industry best practice. Chapter 57 brings all of that within the regulatory framework for the first time. It states that stationary secondary batteries in dwellings shall be installed in a suitable location, taking into account manufacturers' instructions and PAS 63100. In practice, departure from PAS 63100 without substantial documented justification would be very difficult to defend under Part P, and the standard should be treated as the required approach.

PAS 63100:2024 in Practice

PAS 63100:2024, "Electrical Installations: Protection Against Fire of Battery Energy Storage Systems for Use in Dwellings", applies to battery energy storage systems installed in dwellings, regardless of the technology they are paired with. Lead-acid, nickel-based, and lithium-ion systems are all within scope. This standard was already considered best practice. Its direct reference in Chapter 57 means it now sits within the regulatory framework for all battery installations in dwellings.

The practical effect is to define the criteria for a safe installation location. Loft installations are now prohibited, a formal recognition of the fire safety evidence that responsible installers were already acting on. Batteries must be located where appropriate fire separation, ventilation, and emergency access can be provided. Garages, utility rooms with fire-rated separation, and suitably specified external locations are among the compliant choices, provided they meet the specific fire separation, ventilation, and access criteria set out in PAS 63100:2024.

Inverters are not subject to the same prohibition. Where an inverter is located in a loft or other infrequently accessed space, PAS 63100:2024 requires mandatory fire detection to be installed. In practice, many modern systems use hybrid inverter-battery units that are integrated or co-located. Where that is the case, the battery location requirement effectively determines where the inverter must go as well. Designers and specifiers should treat the inverter and battery as a single system for location planning purposes.

For non-domestic settings such as communal plant rooms or block-level storage, Chapter 57 does not apply PAS 63100 directly. It requires that the location and fire protection arrangements are informed by a fire risk assessment, carried out by a competent person and coordinated with any existing obligations under the Regulatory Reform (Fire Safety) Order 2005.

The technical content of this article is drawn from BS 7671:2018+A4:2026 and PAS 63100:2024. Landlords wishing to verify the requirements directly should obtain these publications from the BSI and IET.

Compliance

All notifiable electrical work, including the installation of battery storage systems, must be carried out in accordance with Building Regulations. The Part P requirement of Schedule 1 to the Building Regulations 2010 requires reasonable provision to be made in the design and installation of electrical installations in order to protect persons from fire or injury. Compliance with BS 7671, including the new Chapter 57 requirements, is the accepted means of demonstrating that this requirement has been met. Approved Document P sets out this compliance route in guidance.

Landlords need to ensure their installers are members of a Government-recognised Competent Persons Scheme and able to self-certify their work. Where an installer is not a scheme member, building control approval via a building notice or full plans application is required. Chapter 57 under Amendment 4 must be reflected in all new works from 15 October 2026 onwards.

Installer Competence

Amendment 4 tightens individual competence requirements. Every operative carrying out battery storage installation must now hold their own Level 3 electrical qualification. It is not sufficient to rely on an organisation's Qualified Supervisor alone. Landlords should satisfy themselves that their installer frameworks reflect this requirement at operative level, not only at organisational level.

When Does This Apply

The previous edition of the wiring regulations is formally withdrawn on 15 October 2026. From that date, all new battery storage installations, and any additions or alterations to existing systems, must be designed and certified to Amendment 4. During the transition period between April and October 2026, installers may work to either the current or new standard, though all installers should adopt Amendment 4 now to avoid any risk of non-conformance on programmes spanning that boundary.

Any design being produced now that specifies battery storage should already reference Amendment 4 and PAS 63100:2024 compliance. Given the timescales typical of social housing retrofit, a design produced today will in most cases be built after October. A specification that does not reflect the new requirements now will need revision before installation can proceed, creating delay and abortive cost. Getting the specification right at the outset is the more efficient approach.

The Retrospective Question

Existing certified installations are not affected. Systems that complied with the regulations in force at the time of installation do not require remediation.

The position changes the moment any alteration or addition is made to an existing system after 15 October 2026. Warranty repairs, inverter replacements, and capacity upgrades all constitute alterations for these purposes. Existing maintenance and warranty contracts should be reviewed to confirm that post-October work will be carried out and certified to the new standard. Any existing installations that do not appear compliant with PAS 63100 should be reviewed now, so that landlords understand their obligations before alteration work becomes necessary.

Electrical Installation Condition Reports

The Electrical Safety Standards in the Private Rented Sector (England) (Amendment) (Extension to the Social Rented Sector) Regulations 2025 now require social landlords to have all electrical installations inspected and tested at least every five years by a qualified person, with a copy of the Electrical Installation Condition Report (EICR) provided to tenants within 28 days. These obligations apply from 1 November 2025 for new tenancies and 1 May 2026 for existing tenancies.

Any BESS installation that does not comply with Amendment 4 and PAS 63100:2024 will be noted on the next EICR. The classification applied by the inspector — Code 1 (danger present), Code 2 (potentially dangerous), Code 3 (improvement recommended), or Further Investigation — will depend on their assessment of the risk presented. Where a C1 or C2 finding is made, landlords must complete remedial works within 28 days. Failure to do so carries a maximum financial penalty of £40,000. A C3 finding does not trigger a mandatory remediation obligation. Landlords should ensure their asset management and compliance teams understand this interaction between the EICR cycle and the October 2026 deadline.

Why Compliance Cannot Be Assumed

The requirements in PAS 63100:2024 describe what careful, competent practice looks like. Those requirements are now mandatory. PAS 63100 is directly referenced in Chapter 57 of Amendment 4 of BS 7671, and Part P compliance is most readily demonstrated by following BS 7671. The gap between best practice and regulatory minimum has closed.

Programmes that relied on informal competence arrangements, manufacturer-specific guidance, and assumptions that another party held responsibility are no longer adequate. Battery storage is a high-energy system installed in occupied homes, homes where people sleep, where children grow up, and where fire risk is not an abstract compliance consideration but a direct threat to resident safety. The regulatory framework now reflects that reality.

For landlords running retrofit programmes under the Warm Homes: Social Housing Fund, the question is not whether to comply. It is whether the people designing, specifying, and overseeing your installations have the knowledge and independence to make sure every property, without exception, has a safe and compliant outcome.

The Same Rules Apply to Privately and Self-Financed Installations

Much of the discussion around battery storage in social housing focuses on funded programmes such as Warm Homes: Social Housing Fund Wave 3. A growing number of landlords are also installing photovoltaic panels and battery storage under private finance arrangements, power purchase agreements, or direct self-financing, either alongside a funded programme or entirely independently.

The regulatory obligations are identical regardless of how an installation is paid for. The Part P requirement of the Building Regulations 2010, Chapter 57 of Amendment 4 of BS 7671, and PAS 63100 all apply to any battery storage installation in a dwelling. The funding route does not create or remove any obligation.

What differs is the level of oversight that typically surrounds the work. Funded programmes operate within frameworks of technical monitoring, compliance reporting, and funder requirements that create structural pressure toward specification quality. Privately arranged installations frequently do not. A landlord procuring a battery installation through a finance-and-install package, a lease arrangement, or a direct relationship with a manufacturer or installer may be relying entirely on that supplier to get the specification right, with no independent check.

Bundled finance-and-install packages are commercial products. The party offering them has an interest in making the installation straightforward and cost-effective. They do not always have full awareness of the regulatory context within which the landlord is operating. An installer who is competent at installing may nonetheless produce a specification that is not in accordance with current requirements, particularly during a period of regulatory change.

For landlords exploring private or self-financing routes, independent design oversight is not a funded-programme luxury. It is the mechanism by which a landlord can be confident that what is installed in their homes is compliant, properly certified, and safe for the residents living in them.

This Is Why Competent Retrofit Design Oversight Matters

Regulatory changes like this one do not announce themselves at the point of installation. They arrive in standards documents, amendment notices, and technical specifications. They require someone with the right skills, knowledge, experience, and behaviours working across a programme from design through to certification, to make sure these changes are reflected in what actually gets built.

Under the Building Regulations 2010, as amended by the Building Regulations etc. (Amendment) (England) Regulations 2023 implementing the Building Safety Act 2022 reforms, the Building Regulations Principal Designer (BR PD) dutyholder role was introduced. This role is distinct from the Principal Designer role under the Construction (Design and Management) Regulations 2015, though both may be held by the same person. A competent BR PD, with oversight across the full scope of a retrofit programme, including coordination of the electrical design and specification of high-energy systems such as BESS, is positioned to catch these requirements early, embed them in specifications before procurement, and work alongside the Principal Contractor to ensure installer frameworks and certification routes are fit for purpose before a single battery is ordered.

A competent retrofit designer with genuine oversight of these issues will ensure specifications reflect current requirements before work begins, installer frameworks capture the right competence obligations, and existing systems are correctly assessed when alterations become necessary. Without that oversight, the gap between what is required and what is delivered on site can widen quietly, and the liability sits with the landlord who, as Client, has a statutory duty to make suitable arrangements for compliance.

Article by Rowley Maggs, Strategic Advisor, Ambue Ltd.

Ambue provides retrofit coordination, principal designer services, and architectural design to housing associations and local authorities delivering PAS 2035 retrofit across England. If you would like to discuss how these regulatory changes affect your programme, please get in touch with Rowley Maggs on rowley@ambue.com

This article is provided for general information purposes only. It reflects Ambue's understanding of the regulatory position as at the date of publication and does not constitute professional advice. Readers should not rely on it in place of specific advice tailored to their own circumstances. Ambue can be formally appointed to provide programme-specific guidance.

Rowley Maggs is Strategic Advisor at Ambue Ltd, a RIBA-chartered retrofit coordination and architectural design consultancy working with social housing landlords under the Warm Homes: Social Housing Fund and related programmes.

Image credit: Ambue