UK Regulations

Building Regulations and BS 7671 for Balcony Solar

Plug-in solar occupies a grey area in UK wiring regulations — but it's a well-understood grey area. Here's what the regulations actually say and why most modern UK homes are well-protected.

The Regulatory Grey Area — Explained Clearly

BS 7671, the IET Wiring Regulations (currently the 18th Edition, Amendment 2), is the standard that governs all 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.

BS 7671 does not explicitly address plug-in balcony solar systems. This is the source of the "grey area" — the standard was written before plug-in solar became a product category, and it has not yet been updated to include specific provisions for it. The BSI is currently working to address this.

However, "not explicitly addressed" is very different from "prohibited" or "unsafe." The relevant question is whether existing provisions in BS 7671 adequately cover the safety considerations involved in plug-in solar — and for most modern UK homes, the answer is yes.

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: older-style circuit breakers and fuses were designed with single-directional current flow in mind, and there was a theoretical possibility that reverse current could bypass protective devices. This concern was legitimate for older consumer units but has been substantially addressed by modern wiring.

Older consumer units (pre-2016)

Consumer units with a single whole-board RCD and MCBs (miniature circuit breakers) have RCD protection only on certain circuits. Reverse current from plug-in solar could theoretically feed circuits without bidirectional RCD protection. This is the scenario that prompted the most caution from electricians.

Modern consumer units (post-2016)

Modern consumer units installed since the 2016 amendments to Part P must use RCBOs (Residual Current Breaker with Overload protection) — individual protective devices on each circuit that provide full bidirectional protection. These handle reverse current flow from plug-in solar effectively.

Quick check for your home

Open your consumer unit (fuseboard) and look at the circuit breakers. If each circuit has its own individual device (often labelled RCBO), you have modern protection and are well-covered for plug-in solar. If you have a large RCD switch at the top covering multiple MCBs below it, you have an older-style board. In either case, the practical risk is low, but a newer board is a cleaner installation from a regulatory perspective.

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:

Standard	Applies to	Process
G98	Up to 3.68kW single-phase (or 11.04kW three-phase)	Notification only — submit form, receive acknowledgement
G99	Over 3.68kW (larger systems)	Full application — requires engineering assessment and approval

All balcony solar systems currently on the market — the EcoFlow STREAM (800W inverter), Anker SOLIX (800W), Jackery Navi 2000 (400W), and Plug-in Solar kit (600W) — are well below the 3.68kW G98 threshold. They all fall under G98, which is a simple notification process, not an approval process. You cannot be refused under G98. 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. It requires that certain types of work — including work in kitchens, bathrooms, or outdoors — be carried out by a competent person or notified to the local authority.

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.

This is another area being clarified as the BSI working group develops a specific UK standard for plug-in solar.

What the BSI Working Group Is Doing

In September 2025, the British Standards Institution formally constituted a working group to develop the UK equivalent of Germany's VDE 0100-551-1 — the technical standard for plug-in solar that Germany adopted when it legalised Balkonkraftwerk installations.

The working group includes:

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. This would give electricians, installers, and homeowners clear guidance and move the technology firmly out of the grey area. Publication is expected in 2026, aligned with the government's commitment to create a full regulatory framework.

The informed consensus among electricians

When balcony solar owners ask electricians for their view, the most common informed response is: "It's fine for a modern consumer unit with RCBOs, the risk is genuinely low, but there's currently no formal standard I can point to." That's accurate — and it's what the BSI working group is there to address. The underlying electrical safety position is sound; the paperwork is catching up.