18th Edition Amendment 2: Key Changes Explained

Amendment 2 to BS 7671:2018 was published in March 2022 and became mandatory for all new electrical installations from 27 March 2023. It is the most substantial update to the 18th Edition since its original publication, introducing new sections, modifying existing regulations, and reflecting the rapid growth of distributed energy generation, electric vehicles, and energy storage systems across the UK.

The official designation of the current standard is BS 7671:2018+A2:2022. This replaces the previous BS 7671:2018+A1:2020. The "+A2:2022" suffix indicates that both Amendment 1 (2020) and Amendment 2 (2022) are incorporated into the text.

Amendment 2 does not replace the entire 18th Edition. It modifies, adds to, and clarifies specific regulations within the existing structure. The core principles of BS 7671 remain unchanged — the amendment responds to technological developments and emerging safety considerations that have arisen since 2018.

The most significant addition in Amendment 2 is the new Section 716, which covers prosumer electrical installations. A "prosumer" is defined as a user of an electrical installation who both consumes and produces electricity. This applies to any premises with on-site generation or energy storage — most commonly solar photovoltaic (PV) panels, battery storage systems, and micro-wind turbines.

Before Section 716, the requirements for these installations were scattered across various parts of BS 7671, IET guidance notes, and manufacturer instructions. Amendment 2 consolidates these requirements into a single, coherent section, making it much clearer for installers to design and install prosumer systems correctly.

Key Requirements of Section 716

• ✓Regulation 716.1 defines the scope: installations where electricity is generated, converted, or stored by a prosumer for their own use, with the possibility of feeding surplus back to the public supply network
• ✓Regulation 716.411.3.2.1 addresses protection against electric shock, requiring that inverters and converters disconnect from the supply automatically under fault conditions and that appropriate isolation is provided for maintenance
• ✓Regulation 716.443 requires surge protective devices (SPDs) to be installed where PV or energy storage systems are connected, reflecting the increased risk of transient overvoltages from lightning and switching events
• ✓Regulation 716.514.1 requires clear labelling at the consumer unit, meter position, and point of connection to identify that a prosumer installation is present and to indicate the presence of multiple sources of supply
• ✓Regulation 716.559.3.2 specifies requirements for luminaire emergency conversion systems powered by prosumer installations

Section 716 works in conjunction with the IET Code of Practice for Electrical Energy Storage Systems and the IET Code of Practice for Grid-Connected Solar Photovoltaic Systems. Electricians installing solar PV and battery storage should be familiar with all three documents.

Section 722 (Supplies for Electric Vehicles) was already present in the original 18th Edition, but Amendment 2 introduces significant updates to reflect the rapid growth of EV charging infrastructure and the evolving technical requirements of modern charge points.

Key Changes to Section 722

Regulation 722.411.4.1 has been updated to clarify the RCD requirements for EV charging circuits. Where a Mode 3 charge point is installed (which covers most domestic and commercial wallbox chargers), the circuit must be protected by an RCD with a rated residual operating current not exceeding 30 mA. The type of RCD depends on the charge point: if the charger includes built-in DC fault protection, a Type A RCD is acceptable. If it does not, a Type B RCD (or Type A RCD with a Type B RDC-DD) is required to detect DC residual currents.

Regulation 722.531.2.1 specifies that each EV charging point should be supplied by a dedicated circuit from the distribution board, with its own protective device. This prevents the EV charger from affecting other circuits and simplifies fault finding.

The amendment also addresses the interaction between EV charging and prosumer installations. Where a property has both solar PV/battery storage and an EV charger, the combined requirements of Section 716 and Section 722 must be considered, including load management and the potential for back-feeding.

One of the most discussed changes in Amendment 2 is the updated Regulation 421.1.7, which now recommends the use of arc fault detection devices (AFDDs) in certain types of installations.

What Are AFDDs?

An arc fault detection device monitors the electrical waveform on a circuit and detects the characteristic signature of a dangerous arc fault. Arc faults can occur in damaged cables, loose connections, or degraded insulation, and they can generate enough heat to start a fire. Conventional circuit breakers and RCDs cannot reliably detect arc faults because the current may remain within normal operating ranges.

AFDDs complying with BS EN 62606 are designed to detect both series arcs (where a single conductor is broken or damaged) and parallel arcs (where current arcs between live conductors or between live and earth). When a dangerous arc is detected, the AFDD disconnects the circuit within milliseconds.

When Are AFDDs Recommended?

Regulation 421.1.7 recommends (but does not mandate) AFDDs for final circuits supplying socket outlets up to 32 A in the following situations:

• ✓Premises with sleeping accommodation — including houses, flats, HMOs, care homes, and hotels
• ✓Locations with a risk of fire due to the nature of processed or stored materials — such as workshops, barns, or buildings storing combustible goods
• ✓Locations with combustible construction materials — timber-framed buildings, for example
• ✓Fire-propagating structures — buildings where the construction allows fire to spread rapidly
• ✓Locations with endangered irreplaceable goods — museums, galleries, libraries

Amendment 2 reinforces the requirements for surge protective devices that were introduced in the original 18th Edition. Regulation 443.4 requires a risk assessment to determine whether overvoltage protection is necessary. Where the consequences of an overvoltage event include risk to human life, disruption to public services, or loss of irreplaceable cultural heritage, SPDs are mandatory.

In practice, the proliferation of sensitive electronic equipment in modern homes and businesses — along with the growth of solar PV and EV charging — means that SPDs are now recommended for most new installations. Type 2 SPDs installed at the consumer unit provide a cost-effective first line of defence against transient overvoltages caused by lightning strikes and switching events on the supply network.

Section 716 specifically requires SPDs for prosumer installations, recognising that solar PV arrays and battery storage systems are particularly susceptible to lightning-induced overvoltages due to the extended cable runs between roof-mounted panels and ground-level inverters.

Beyond the headline changes, Amendment 2 includes numerous smaller modifications and clarifications that affect day-to-day electrical work.

Updated Definitions (Part 2)

Part 2 of BS 7671 has been expanded with new definitions reflecting the technologies addressed in Amendment 2. Key additions include "prosumer's electrical installation", "energy storage system (ESS)", "electrical energy storage system (EESS)", and "onshore power supply". These definitions are important because they establish the precise scope of the associated regulations.

Section 710: Medical Locations

Section 710 has been updated to align with the latest requirements for electrical installations in hospitals, clinics, and other medical facilities. Changes include updated requirements for insulation monitoring devices in IT medical systems and clarified requirements for standby power supplies.

Onshore Power Supply for Boats and Vehicles

New requirements have been added for onshore power supply installations, reflecting the growth of electrical connections for boats in marinas and vehicles in campsites. These installations present specific safety challenges due to the combination of outdoor exposure, water proximity, and connections to movable equipment.

Energy Efficiency (Appendix 17)

Appendix 17, originally introduced in Amendment 1, has been further expanded. It provides guidance on how electrical installation design can contribute to energy efficiency — including power factor correction, efficient lighting design, and the consideration of energy storage as part of the installation design process. While not mandatory in the traditional sense, Appendix 17 reflects the growing importance of sustainability in electrical installation design.

For working electricians, the practical impact of Amendment 2 can be summarised in a few key areas:

• ✓Solar PV and battery storage installations now have a clear regulatory framework in Section 716, replacing the previous patchwork of guidance documents
• ✓EV charger installations must comply with the updated Section 722 requirements, particularly regarding RCD selection and dedicated circuits
• ✓AFDDs should be considered for domestic and certain commercial installations, and the design decision should be documented
• ✓SPDs are effectively standard for most new installations, especially those with PV, battery storage, or EV charging
• ✓Labelling requirements have been strengthened for installations with multiple sources of supply (prosumer installations)
• ✓The 2382-22 exam now includes questions on all Amendment 2 content, so updating your qualification is essential

If you hold a 2382 certificate from before Amendment 2, it is strongly recommended that you update to the current 2382-22. Most competent person schemes require this, and it demonstrates to clients and employers that your knowledge is current.