Building Regulations and BS 7671 for Balcony Solar

Where BS 7671 Actually Sits

BS 7671, the IET Wiring Regulations (currently BS 7671:2018+A4:2026, the 18th Edition as amended by Amendment 4), is the standard that governs fixed electrical installations in the UK. It is not a statutory instrument — compliance is not directly enforceable by law — but it is incorporated by reference into Building Regulations Part P (Electrical Safety in Dwellings) and is treated as the definitive standard for safe electrical work.

It is often said that BS 7671 has nothing to say about plug-in solar. That is not correct. The Interim Product Specification names BS 7671:2018+A4:2026as one of the documents it must be read alongside, and in its assembly and commissioning requirements it points directly at a specific provision: manufacturers must state where connection requires modification to the final circuit, identifying that as work only a qualified electrician may do, “e.g. replacement of the overcurrent protection device of the concerned electric circuit in accordance with BS 7671 Section 551.7.2 for the connection of a plug-in solar device”.

So there is an identified section of the Wiring Regulations for this. What the specification is doing is drawing a line between the device — which you may plug in yourself — and any change to the fixed wiring behind the socket, which you may not.

From 27 August 2026: ESQCR Regulation 22(1)(c)

SI 2026 No. 848does two separate things. Regulation 2 amends the Plugs and Sockets etc. (Safety) Regulations 1994 to create an approval route for a standard plug supplied with a “plug-in microgenerator”. Regulation 3 amends the Electricity Safety, Quality and Continuity Regulations 2002, substituting regulation 22(1)(c) so that where the source of energy is a plug-in microgenerator, it must comply with the Plug-in Solar Device Interim Product Specification.

The explanatory note puts it directly: the effect is that a plug-in microgenerator “must not be installed or operated unless it complies with the Plug-in Solar Device Interim Product Specification”. That is the limb that governs use, and it extends to England, Wales and Scotland only — regulation 1(4) of the instrument. The plug approval limb extends to Northern Ireland as well, but the specification itself records that its application to Northern Ireland is subject to further consideration and may require amendment.

Until 27 August 2026, the government's position is that plug-in solar devices “cannot be sold or used lawfully in the United Kingdom, as they do not currently comply with the Plugs and Sockets etc. (Safety) Regulations 1994 (PSSR) or the Electricity Safety, Quality and Continuity Regulations 2002 (ESQCR)”.

The Technical Concern: Reverse Current Flow

The main technical concern with plug-in solar connected to a ring circuit is the direction of current flow. In a standard ring circuit, current flows from the consumer unit (fuseboard) to appliances. A plug-in solar system connected to a socket on that ring circuit feeds current in the opposite direction — potentially back towards the consumer unit.

The concern is real but it is not the one usually described. It is not that reverse current bypasses a breaker. It is DC leakage desensitising a residual current device. The government's technical annex explains that older, mostly type AC, RCDs can be desensitised by small amounts of direct current leaking back onto the supply — a problem it describes as “not unique to plug-in solar devices since most modern switch-mode power supplies leak small amounts of DC back onto the supply”.

IPS version 2 responds to this by capping residual DC current from the inverter at 5 mAat maximum output. Crucially, the government does not treat that as settling the matter: it is “undertaking further electrical testing to assess whether residual direct current injection from plug-in solar devices at 5mA maximum levels could still result in desensitisation of older (type AC) RCBOs and other protective devices under UK installation configurations”, and the 5 mA figure “will be reviewed once these results are available”.

What Counts as a Modern Consumer Unit

There is a widespread claim that consumer units installed since January 2019 must use RCBOs, and that an older board with a single RCD over a row of MCBs is therefore inadequate for plug-in solar. The specification does not draw that line. Its guidance for identifying protective devices treats two configurations as equally normal:

“Modern electrical installations typically have configurations with RCBOs providing overcurrent and residual current protection for individual circuits, or miniature circuit breakers (MCBs) per circuit with residual current protection provided by shared upstream RCD.”

The specification's own footnote adds that installations protected by MCBs with an upstream RCD “may also be acceptable, subject to verification through further testing now being undertaken by DESNZ”. So a shared-RCD board is not disqualified; it is one of the things still being checked.

The line the specification actually draws is between modern protective devices of either kind and older installations using wired fuses, which “may not provide individual protection for each circuit” and lack individual switches. Where a consumer unit uses wired fuses, is not clearly labelled, or is of unknown condition, users “shall be advised to seek inspection and assessment by a qualified electrician before installing the product”.

G99 vs G98: Which Applies to Balcony Solar?

Engineering Recommendation G98 and G99 are the DNO (Distribution Network Operator) connection standards for small generators. The distinction is based on output capacity:

Plug-in solar sits far below the G98 threshold — the specification caps apparent power at 800 VA and output current at 3.5 A. What matters is not the threshold but the obligation: IPS version 2 requires the product to carry a “statement that notification to distribution network operator (DNO) about connection and disconnection is mandatory, including a link to instructions on how to do so”.

Note also that G98 sets its own limit that the specification does not override. G98 Issue 2 Amendment 1 2026 restricts installations to one device per household, and the specification says that “applies unless and until that is amended”. See our full G98 notification guide.

Building Regulations Part P: Does It Apply?

Part P of the Building Regulations (Electrical Safety in Dwellings) applies to electrical installation work in dwellings. In England, the work that must be notified is a closed list in regulation 12(6A): installing a new circuit, replacing a consumer unit, and altering an existing circuit in a special location such as a room containing a bath or shower. Kitchens and outdoor work were removed from that list in April 2013, so they are no longer notifiable in England on their own. Wales kept the wider list, which still catches kitchens and special locations.

Plug-in solar is connected via a standard socket outlet. This is not a fixed installation — the system can be unplugged and removed. The view of most electrical professionals is that plug-in solar does not constitute "electrical installation work" under Part P because it involves no modification to the fixed wiring of the building. You're not adding circuits, moving cables, or modifying the consumer unit.

The specification draws the same line. It requires manufacturers to state that “any necessary testing and modifications of the building's electrical system ... shall only be performed by professional electricians” in accordance with the distribution code, G98 and BS 7671, and that any work touching the final circuit — its example is replacing the circuit's overcurrent protection device under BS 7671 Section 551.7.2 — is work only a qualified electrician may do. Plugging the device in is yours; anything behind the socket is not.

What the BSI Working Group Is Doing

Two dates get conflated here, and our own legalisation timeline has them right where an earlier version of this page did not. In September 2025 the British Standards Institution announced a work programme covering plug-in solar equipment — preparatory scoping, not a commission. The BSI was formally commissioned to develop a dedicated UK standard as part of the 24 March 2026 government announcement. This page previously said the commission happened in September 2025; that was wrong.

The government has committed to succeeding the interim specification: its consultation response says “work will begin on the development of longer-term standards to succeed the IPS”, and the specification itself states it “may be modified from time to time or superseded to allow for new technical innovations in plug-in solar as they arise and to reflect future British Standards related specifically to plug-in solar products”. No publication date for the enduring standard has been announced; estimates of 2027 or later circulate widely but are projections rather than commitments.

The working group is expected to include:

• Representatives from the Institution of Engineering and Technology (IET)
• BEAMA — the electrical equipment manufacturers' trade association
• Distribution Network Operators (DNOs)
• Solar Energy UK
• Consumer advocacy organisations
• Product manufacturers including EcoFlow and Anker

The expected output is a BSI Publicly Available Specification (PAS) or a new section of BS 7671 covering plug-in solar installations. Membership and output format are our own expectations rather than published commitments, so treat them as such.