BS 7671:2018+A4:2026 introduced "Prosumer’s low voltage electrical installation(s)" as a distinct installation type governed by the new Chapter 82 (Part 8 — Functional Requirements). This guide explains what counts as a prosumer installation, why Chapter 82 adds dedicated requirements, and what UK electricians must check on every installation that both consumes and produces electricity.
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Written and reviewed by Andrew Moore, founder of Elec-Mate, against BS 7671:2018+A4:2026, IET Guidance Note 3 and the IET On-Site Guide.
A prosumer's low voltage electrical installation (PEI) both consumes energy from the supply and produces energy that may be exported or stored — combining the traditional consumer and generator roles. BS 7671:2018+A4:2026 governs these installations under the new Chapter 82. Typical UK examples are solar PV, battery storage, small wind, micro-CHP and EV vehicle-to-grid.
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The word "prosumer" combines producer and consumer — an installation that does both. Traditionally, BS 7671 treated electrical installations as either consumers (drawing power from the grid) or generators (feeding power to the grid). BS 7671:2018+A4:2026 formally recognises that modern UK installations increasingly do both — and need their own treatment under the new Chapter 82 (Part 8 — Functional Requirements).
Regulation 110.1.2(d) explicitly brings prosumer’s low voltage electrical installations (PEI) within the scope of BS 7671, including those located external to buildings — so roof-mounted PV arrays, ground-mounted solar fields, and externally sited BESS enclosures all fall within scope. The defined term in Part 2 is unambiguous: a prosumer is an "entity or party which can be both a producer and a consumer of electrical energy".
Consumer
Draws power from the supply only.
Generator
Feeds power to the supply only.
Prosumer (PEI)
Does both — consumes and produces / stores.
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A prosumer installation can be built around any source that lets the premises produce or store its own energy alongside the grid connection. The most common UK sources are below. The DC-side and array-side requirements for solar are covered in detail in our Section 712 Solar PV guide.
Photovoltaic (PV) generators
The most common UK prosumer source. The grid supplies what the PV cannot; the system exports surplus.
Battery energy storage (BESS)
Stores PV or off-peak grid energy for later use; may also export in V2G or ancillary-service roles.
Small wind turbines
Uncommon at domestic scale in the UK, but a recognised prosumer source where present.
Micro-CHP units
Combined heat and power with grid synchronisation; increasingly seen in district heating schemes.
EV vehicle-to-grid (V2G)
The EV battery exports back to the grid during peak hours. Growing under DNO V2G trials.
Whichever source is present, the classification under BS 7671 is the same: once an installation can both consume and produce, it is a prosumer’s electrical installation and Chapter 82 applies.
Before A4:2026, prosumer installations were inspected under the general electrical installation rules with some cross-references to Section 712 (Solar PV) and the IET Code of Practice. A4:2026 introduced Chapter 82 because prosumer installations have specific failure modes that do not exist in traditional consumer-only installations:
Bidirectional power flow
Protective devices and bonding must accommodate fault current flowing in either direction. In island mode the short-circuit current has a different magnitude from connected mode (Reg 826.1.2.1).
Isolation arrangements (Reg 826.1.1.4)
"Switched off" at the consumer unit no longer means "isolated from generation" if PV or a battery can back-feed the busbar. A main switch suitable for isolation is required per source, plus a durable warning notice — or a suitable interlock.
Labelling (Reg 514.15.1)
The responsible person, future electricians and emergency services need clear warning notices at the origin, the meter position, the consumer unit and every point of isolation.
Earthing co-ordination
Solar PV DC strings, battery storage and the AC distribution system must share an earthing strategy that doesn't create earth loops or compromise protective device operation.
Energy management (Section 825)
Where an electrical energy management system (EEMS) controls energy flow, its type and characteristics must be selected for compatibility with the sources used; Section 825 sets the requirements for EEMS in prosumer installations.
Before A4:2026, an inspector could complete an EIC without explicitly addressing prosumer equipment — any non-compliances surfaced as general observations. Chapter 82 makes prosumer-specific inspection a clearly identified part of the design, erection and verification process for any installation with local production or storage of energy.
When confirming prosumer compliance, you are verifying the prosumer-specific items below are all in order. Several of these reference standards outside BS 7671 (the ENA Engineering Recommendations and the IET Codes of Practice) — they still form part of the overall compliance picture even though BS 7671 does not set their numeric thresholds.
PV strings and battery storage create DC fault current paths that a basic Type AC RCD will not reliably detect. BS 7671 is specific about the PV AC supply circuit: Regulation 712.531.3.5.1 requires that where an RCD is used for protection of the PV AC supply circuit it shall be of Type B (to BS EN 62423 or BS EN 60947-2), unless one of the listed exceptions applies — for example where the inverter or installation provides at least simple separation between the AC and DC sides, or the inverter manufacturer states a Type B is not required.
Generally NOT suitable where DC fault paths exist
Permitted by some inverter manufacturers; check the manual
Used for specific frequency-controlled loads
Required for the PV AC supply circuit unless an exception in Reg 712.531.3.5.1 applies
The minimum acceptable type for any given circuit ultimately depends on the inverter topology and the manufacturer’s instructions — always consult the inverter’s installation manual alongside Reg 712.531.3.5.1.
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The single most important behavioural difference for a prosumer installation is that turning off the consumer-unit main switch no longer guarantees the busbar is dead — a PV inverter or battery can back-feed it. Regulation 826.1.1.4 therefore requires a main switch suitable for isolation (for example a switch-disconnector) for each source of supply, plus a durable warning notice positioned so that anyone operating one switch is warned to operate all of them to achieve isolation. Alternatively, a suitable interlock system is provided.
Reg 514.15.1 requires the warning notice to be durably marked and to identify the relevant point(s) of isolation. An example notice is given at Figure 11E of Appendix 11.
The Energy Networks Association (ENA) Engineering Recommendations G98 and G99 govern how UK prosumer installations connect to the public distribution network — these are ENA documents, not part of BS 7671. The installer’s job is to verify G98/G99 compliance and complete the DNO notification or application.
ENA G98 — "Notify"
ENA G99 — "Apply"
The ENA maintains a published list of type-approved G98/G99 inverters. Confirm the installed equipment is on the list before signing off the prosumer inspection.
During EICR inspection of existing prosumer installations, the following defects are commonly found and become coded observations. The C1 / C2 / C3 classifications below are the inspector’s typical coding for each scenario — always classify against the actual risk found on site.
Missing G98 notification or G99 approval
The inverter is installed but the DNO was never informed — the network may not be designed for the export capacity.
Inappropriate RCD type
A Type AC RCD on a circuit with PV/battery DC fault current paths may not detect DC components, leaving the circuit effectively unprotected.
Anti-islanding test failure (still exporting)
If the inverter continues to energise the network on simulated grid failure this is a live-island hazard. C2 if it disconnects but slower than required.
Inadequate isolation arrangements
No DC isolator between PV string and inverter, or no AC isolator separate from the main consumer unit.
Missing or incorrect labelling
No warning notice indicating PV/battery presence per Reg 514.15.1. Severity depends on whether other warning provisions exist.
Earthing conflicts (earth loop)
PV DC string earthed both at the inverter and at the array. C2/C1 only if symptoms of fault current circulation are present.
Battery installed without ventilation provision
Manufacturer's ventilation provision omitted — overheating and thermal-runaway risk.
See our RCD type selection guide for more on why Type AC is the most frequent prosumer coding issue.
A compliant prosumer installation has a paper trail beyond the EIC itself. Capture all of the following and keep them with the certification:
EIC (BS 7671) for the AC installation
Covers the consumer-side circuits including the prosumer interface.
MCS certificate (where applicable)
Microgeneration Certification Scheme certificate for the PV / battery / heat pump. Required for the Smart Export Guarantee (and legacy feed-in tariffs).
G98 notification or G99 approval
DNO confirmation of grid-connection compliance.
Manufacturer's commissioning certificate
The inverter and battery manufacturer's certificate showing the equipment was correctly set up.
Circuit diagrams and labelling schedule
Typically required by the IET Code of Practice for Electrical Energy Storage Systems above a threshold.
Battery storage risk assessment
Fire and thermal-runaway considerations, especially for installations in occupied buildings.
Prosumer inspection items should be recorded clearly within the electrical installation report rather than buried in the general schedule, so the next person can see at a glance that the alternative or additional source of supply was inspected. Our digital EIC includes a dedicated prosumer workflow so this is captured automatically.
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