Last reviewed: 4 September 2026. Read against the published document: DESNZ, Plug-in Solar Device Interim Product Specification, version 2.0, July 2026. Clause references below are ours, taken from that text.
The law that legalised plug-in solar in Great Britain is short and says almost nothing about the product. It sets an 800 W AC ceiling, excludes storage, and then points at a separate document for everything else. That document is the Interim Product Specification, published by DESNZ in July 2026 alongside the government’s consultation response — 45 pages that decide what a compliant kit contains, how it must behave when you pull the plug, what its instructions must warn you about, and whether it may be sold here at all. It binds manufacturers, not you. But almost every practical question a household asks is answered in it rather than in the statutory instrument, and knowing which document says what is the difference between reading a rule and repeating a rumour.
Where it sits: two documents, two jobs
SI 2026/848 amends the Plugs and Sockets etc. (Safety) Regulations 1994 and the Electricity Safety, Quality and Continuity Regulations 2002. It defines a “plug-in microgenerator” by its maximum rated AC output — not exceeding 800 watts — and excludes any device designed to import electricity from the installation in order to store it for later supply. It then works by permitting approval of standard plugs for devices that comply with the specification. That is the hinge: the law makes the specification operative without reprinting it.
So when you see the figure 2,000 W DC quoted as “the law”, it is not. It is clause 4.1 of the specification. The same is true of the 3.5 A current limit, the 5 A plug fuse, the 100 ms disconnection time and the ban on extension leads. They are binding on the product, and they are not in the SI. See when plug-in solar became legal for the legislative side.
What “interim” means
It means what it says. Version 2.0 replaced the consultation draft, and the document is explicitly a first step: the government has said a permanent specification will follow, and the document itself is peppered with notes about requirements that may change — most conspicuously the number of devices you may have, which the specification writes as one per final circuit while acknowledging that G98 currently restricts it to one per household “unless and until that is amended”. A second, quieter note flags that installations protected by MCBs with an upstream RCD “may also be acceptable, subject to verification through further testing now being undertaken by DESNZ”.
A kit bought today is compliant against the interim document. When the permanent one arrives we will rewrite this page and date the rewrite, rather than editing a sentence and hoping nobody noticed.
The document, clause by clause, and what each one decides for you
| Clause | Requirement | What it decides for you |
|---|---|---|
| 1 (scope) | Single phase, up to 253 V AC, 50 Hz, apparent power not exceeding 800 VA; one product per household final ring circuit, subject to G98 | The whole shape of the product category — and the number limit that G98 currently tightens to one per household |
| 4.1 | Maximum apparent power ≤ 800 VA; maximum current ≤ 3.5 A; total PV module DC power ≤ 2,000 W; professional assessment advised above 960 W | The four numbers that define a compliant kit. Only the 800 W figure also appears in the SI |
| 4.2.2 | Up to four PV modules; no more than two in series per string; open-circuit voltage at the inverter inputs not exceeding 120 V DC; no Y-connectors | How far you may oversize the array, and why you cannot just add a fifth panel |
| 5.4 | IP55 or better for outdoor components and outdoor plugs and sockets; better than IP44 for indoor-only parts | Whether the inverter may live outside, and what the outdoor socket must be |
| 5.5.1 | Mounting system supplied as part of the kit, with a full component list and a structural analysis for UK wind and snow loads; cable ties, rope, string, adhesive tape, bungee cords and straps not permitted | The single most-ignored clause. A kit “with straps” is not a kit with a mounting system |
| 5.7 | Smooth DC residual current to the mains not exceeding 5 mA; must not adversely affect upstream RCDs | Why the specification cares so much about what protects your circuit |
| 5.8 | No installation on ACM or MCM cladding, HPL cladding, timber cladding, timber balconies, or buildings under external wall remediation | A hard stop for a large number of flats, whatever the lease says |
| 6.2.3.1 | Multi-way adaptors, travel adaptors, RCD adaptors and plug convertors not permitted | No extension leads. See extension leads and plug-in solar |
| 6.2.3.2 | BS 1363-1 plug, partially insulated pins, non-rewireable moulded plug with a BS 1362 fuse not exceeding 5 A | Why a Schuko kit with an adaptor is not a compliant kit |
| 6.2.3.3.3 | On disconnection from the mains, automatic disconnection within 100 ms and plug-pin voltage below 34 V within 100 ms; additional contact protection removes dangerous voltage within 2 s | The reason it is safe to pull the plug on a live generator |
| 7 | Type tested to G98, registered on the ENA Type Test Register and verified as compliant before being placed on the market; submission alone is not compliance | The check you can do yourself in two minutes. See how to spot a non-compliant kit |
| 8.2.3 | Permanent marking with manufacturer details, ratings, IP and protective class, the one-device statement, and that DNO notification of connection and disconnection is mandatory; plus a durable label for the consumer unit | What should be printed on the product, and what should be in the box |
| 8.3.2–8.3.4 | The mandated instruction content: cladding and remediation warnings, the battery warning, the RCBO check, circuit identification guidance, the extension-lead prohibition, DNO registration with a QR code, insurance and permissions | The manual is a compliance document, not a leaflet — read it before you buy |
| 9 | Type tests and routine tests; a technical file retained for at least 10 years after last manufacture | What “type tested” actually involved |
Three things in the document that surprise people
It is a translation, not an invention
The specification is built on DIN VDE V 0126-95, the German standard for plug-in solar devices, described in the introduction as the primary technical and safety reference case, adapted for the UK context — with a note that where the two differ, the UK specification takes priority. The 34 V figure carries an explicit note saying it is taken from the German standard. On top of that sits a study DESNZ commissioned specifically about British conditions, Plug-in PV Systems in the United Kingdom: Electrical Safety, Compatibility and Implementation Considerations, which examined plug-in PV on UK ring final circuits and concluded that products used in Germany and elsewhere are safe on UK circuits under defined limits. The specification then defines those limits. See what the UK can learn from German balcony solar.
Fire safety is treated at system level, including the wall behind the panel
Clause 5.8 does not stop at the module and the inverter. It considers “the surface to which it is intended to be installed”, bans installation on several cladding types and on timber balconies outright, and requires the instructions to cover escape routes, fire spread between dwellings and boundary walls between properties. There is a related requirement that the module’s outermost substantial layer — in most cases the backsheet — achieves a reaction-to-fire performance equivalent to Euroclass B-s3, d2 to BS EN 13501-1, with a note conceding that no dedicated fire classification exists for PV modules and that this was adopted as the nearest appropriate benchmark. That is an unusually candid piece of drafting.
It expects you to press the test button
Clause 8.3.4 is about something most people never think about: older residual current protection can be desensitised by devices that leak DC current into an AC circuit — plug-in EV chargers, IT equipment, power supplies and plug-in solar among them. The specification’s answer is that consumers should be told to press the RCBO’s test button periodically while the plug-in solar unit is producing power, and to contact a competent electrician about replacing the RCBO if it does not trip immediately. It is the only routine maintenance task the document asks of you, and it takes ten seconds.
Where the specification stops
It is a product specification. It does not give you a right to attach anything to a building you do not own — it says the opposite, requiring manufacturers to tell you that permissions from the owner, landlord, freeholder or managing agent, along with planning permission and listed building consent, are your responsibility. It does not touch export payments; a plug-in kit has no MCS certificate and no export meter point, so the Smart Export Guarantee does not reach it. It does not replace G98, which is where the notification duty and the current one-per-household limit live. And it does not make any of your fixed wiring somebody else’s problem: testing and modification of the building’s electrical system, it says, “shall only be performed by professional electricians in accordance with low voltage connection regulations such as the distribution code, G98 and the IET Wiring Regulations BS 7671”.
Further reading: the rules from 27 August 2026, can I have two kits, what is in a plug-in solar kit and microinverters explained.
Frequently asked questions
Does the specification apply in Northern Ireland?
No. G98 applies to Great Britain; Northern Ireland’s connection requirements are set out in G98/NI, and the specification’s own footnote says its application to Northern Ireland “is subject to further consideration and may require amendment”. SI 2026/848’s use provision extends to England, Wales and Scotland only. See plug-in solar in Northern Ireland.
Which edition of BS 7671 does it refer to?
BS 7671:2018+A4:2026, listed in the applicable standards. The specific provision it names for plug-in solar is section 551.7.2, on final circuits supplied by both the distributor and a generator.
Can I read the specification myself?
Yes, and you should if you are buying. It is published as a PDF from the GOV.UK consultation page and linked below. Be careful which version you have: an earlier draft was withdrawn and superseded by version 2.0.
Who enforces it?
It bites on manufacturers and, through them, on retailers placing products on the market — with ENA registration as the gate. General product safety enforcement sits with Trading Standards and the Office for Product Safety and Standards. Nobody enforces it against a householder in a garden.
Is a compliant kit therefore a good kit?
It is a lawful one. Efficiency, warranty terms, monitoring and the quality of the mounting hardware are separate questions the specification barely touches — see choosing a kit.
Primary sources.
DESNZ, Plug-in Solar Device Interim Product Specification version 2.0, July 2026 (PDF) ·
DESNZ, plug-in solar consultation, government response and impact assessment ·
SI 2026/848 (legislation.gov.uk) ·
ENA Type Test Register ·
IET, BS 7671 Requirements for Electrical Installations.
General information, not legal or electrical advice — see our editorial methodology.