BS 7671 Amendment 4 Technical Guide

The Shift to BS 7671:2018+A4:2026

Amendment 4 to the 18th Edition Wiring Regulations came into effect in 2026. It reflects the growth of prosumer installations (solar, batteries, EV), modern power quality challenges, and stricter safety requirements for stationary batteries. Here's what matters for your project.

Chapter 82: Prosumer Installations

Chapter 82 covers the integration of solar PV and battery storage with the mains supply. Key points:

• Island mode and export: Requirements for systems that can island (run independently) or export to the grid.
• Energy storage systems (ESS): Design, installation and protection of stationary batteries – including lithium-ion and lead-acid.
• Prosumer's electrical installation (PEI): The consumer's side of the interface – metering, isolation, and coordination with the DNO.

If you're adding solar, a battery, or an EV charger, your electrician must follow Chapter 82. We design and install to these requirements across Margate, Ramsgate and Broadstairs.

Power Quality: Harmonics and Modern Electronic Noise

Modern loads – LED drivers, inverters, EV chargers, IT equipment – can introduce harmonics and electromagnetic interference. Amendment 4 addresses:

• Harmonic distortion: Limits and mitigation for equipment that draws non-linear current.
• EMC (electromagnetic compatibility): Reducing interference between installations and with other systems.
• Voltage fluctuations: Impact of large or variable loads (e.g. heat pumps, EV charging) on supply quality.

Proper cable sizing, protective device selection, and sometimes power factor correction or filtering are part of compliant design. We assess your load profile and design accordingly.

Safety First: Stationary Batteries and Signage

Amendment 4 strengthens requirements for stationary secondary batteries (e.g. home battery storage):

• Ventilation and thermal management: Batteries must be installed in suitable environments with adequate cooling and, where required, ventilation.
• Fire separation: Separation from living areas and escape routes where specified.
• Signage and documentation: Clear labelling of battery locations, isolation points, and emergency procedures. Updated schedules and diagrams.
• Competence: Installers must be competent in the specific technology (e.g. lithium-ion ESS).

We install battery storage with full compliance to these safety requirements and provide the correct documentation and signage.

Our Tools

We work to the latest BS 7671 and use the current On-Site Guide (OSG) for design and verification. Our reference set includes the 18th Edition Amendment 4 and the companion OSG – so your installation is designed and tested against the correct standards.

Recommended Tool: Buy the Orange Book (£35)