Plug-in solar in the UK is governed by a short list of documents and a shorter list of acronyms. This glossary defines the terms that turn up on a plug-in solar panel listing, on a DNO form and in the new regulations, in plain English, with the instrument or standard each one comes from named.
Every entry links to the page that owns the topic. If you want the narrative on how balcony solar power works rather than the definitions, start with the beginner’s guide to balcony solar.
The unit mismatch you’ll hit on your first page of reading
SI 2026 No. 848 caps a plug-in microgenerator at 800 watts of AC output. The Interim Product Specification it points to caps the same device at 800 VA, which isn’t the same unit. The instrument says "800 watts" twice and never uses the words apparent power, volt-amp, reactive or power factor. The specification never uses the word watt. Nothing published reconciles them.
Plug-in solar panel terms, A to Z
A
Anti-islanding. The inverter function that shuts generation down when the grid supply disappears, so a device can’t keep a dead section of network live while an engineer works on it. Regulation 22(2)(b) of the ESQCR requires the source of energy to be "configured to disconnect itself electrically from the parallel connection when the distributor’s equipment disconnects the supply". The specification wants that inside 100 milliseconds, with accessible plug pins below 34 V. It’s proven by type testing, and it’s why a plug-in kit won’t power your home in a blackout. See our electrical safety guide.
Apparent power (VA). Voltage multiplied by current, measured in volt-amps. It’s what the wiring, the plug and the fuse have to carry. Real power in watts is apparent power times the power factor, a number between 0 and 1, so watts can never exceed VA. The 800 VA versus 800 W problem is two documents picking different units for one ceiling.
B
Balkonkraftwerk. German for "balcony power plant", the ordinary German word for a plug-in solar kit. German devices are built to DIN VDE V 0126-95, connect under VDE-AR-N 4105, and register through the Marktstammdatenregister rather than a grid operator. None of that satisfies the UK route, as importing a German kit explains.
BS 1363. The British Standard behind the familiar UK 13 A fused three-pin plug and the wall outlet it goes into. It restricts using a plug to connect an electricity-generating device to a socket-outlet, which is the obstacle the new instrument works around. The specification requires a factory-fitted BS 1363 plug with a 5 A fuse and partially insulated pins, and checking a kit is legal starts there.
BS 7671. The IET Wiring Regulations, the standard British electrical installations are built to. The current edition is BS 7671:2018+A4:2026, Amendment 4, published on 15 April 2026, and the specification requires compliance with it. BS 7671 never anticipated generation being injected through a socket-outlet, which is the ambiguity that held plug-in solar back. See building regulations and BS 7671.
C
Chattel and fixture. Property-law terms deciding whether something belongs to you or to the building. A chattel is moveable personal property; a fixture has become attached in a way that means it passes with the building on sale or at the end of a lease. A panel on a railing clip is personal property, which underpins the deposit position for renters and taking a kit when you move.
D
DNO (distribution network operator). The company that owns and maintains the cables in your street. It isn’t the company that bills you. Six operators cover fourteen licence areas in Great Britain, and Northern Ireland has NIE Networks. Telling yours about a plug-in solar system is mandatory, and the specification makes the product carry that statement plus a QR code to the guidance. See DNO notification explained.
E
ENA Type Test Register. The Energy Networks Association’s register of type-tested generation equipment, searchable on ENA Connect Direct. The specification requires a device to be listed and verified compliant, because registration alone isn’t enough. At the last check, on 11 August 2026, four devices sat under the "Plug-in Solar" type and all four were assessed non-compliant. See the certified kit tracker and what the register shows.
ESQCR 2002. The Electricity Safety, Quality and Continuity Regulations 2002, SI 2002/2665. Regulation 22, "Parallel operation", governs running a source of energy alongside a distributor’s network. Regulation 3 of the amending instrument rewrote regulation 22(1)(c) so a plug-in microgenerator must comply with the specification. That’s the limb making use lawful, and whether it’s legal to use plug-in solar turns on it.
G
G98 and G98/NI. Engineering Recommendation G98 is the Energy Networks Association route for connecting type-tested micro-generation up to and including 16 A per phase, roughly 3.68 kW single phase. The specification’s footnote says G98 "applies to Great Britain only", with Northern Ireland’s requirements sitting separately in G98/NI, administered by NIE Networks as Issue 1. G98 Issue 2 Amendment 1 2026 also restricts a household to one device, which is the limit that binds. See the G98 notification route and Northern Ireland’s position.
H
Half-cut cell. A module design in which every cell in the solar panel is cut in two, halving the current through each half and cutting the resistive losses that rise with current. The module is wired as two halves, so shade across one row doesn’t shut the whole panel down. Our panel buyer’s guide covers what else to read on a datasheet.
Higher-risk building. Section 65(1) of the Building Safety Act 2022 defines one as a building in England that "(a) is at least 18 metres in height or has at least 7 storeys, and (b) contains at least 2 residential units". It’s England-only, and it isn’t the same test as clause 5.8 of the specification, which prohibits certain surfaces and carries no height or storey threshold. Fire safety in flats separates the two.
I
IPS (Interim Product Specification). The Plug-in Solar Device Interim Product Specification, published by DESNZ. Version 1.0 went out for consultation on 16 June 2026; version 2 landed on 16 July 2026 with the government response. The instrument names version 2 by publication date, so that’s the one with legal effect. It bridges the gap until BSI publishes a full UK standard. Our read of what it requires goes clause by clause.
Three words this glossary won’t use about the register
Every plug-in solar device on the ENA register is currently assessed "Non-compliant", a sub-category of "Further Information Required". ENA’s wording is that the device "cannot be deemed compliant at this stage" and "will be reviewed again". That isn’t the same as failed, rejected or unsafe, and coverage reaching for those words describes something the register doesn’t say.
M
MCS (Microgeneration Certification Scheme). The certification usually used to show an installation and its installer are suitably certified. Ofgem’s export guidance gives MCS as the example and accepts equivalent schemes, so it isn’t the only door. The difficulty for a plug-in kit is that there’s no installer to certify, which getting SEG without MCS works through supplier by supplier.
Microinverter. A small inverter converting DC to AC for one or two panels rather than a whole array. Plug-in kits use them because what goes into the wall has to be AC, and because it’s the component listed on the ENA register. Its declared rating meets the 800 VA and 3.5 A limits, not the panels’. Our comparison of the main brands sets them side by side.
MPAN (Meter Point Administration Number). The long supply number on your electricity bill, usually printed in a bordered grid. The first two digits of the bottom row are the distributor ID and identify your network operator without guessing from a map. You’ll need it on a notification form, and how to fill in a G98 form has the full table.
MPPT (maximum power point tracking). The inverter function that hunts continuously for the combination of voltage and current at which a solar panel delivers most power. Shade, temperature and time of day all move that point. Two independent MPPT channels track two panels separately, so a shaded one doesn’t drag its neighbour down, which is why what shade costs a kit is partly an inverter question.
P
Permitted development. Planning rights letting certain work proceed without a planning application. Solar equipment sits under Class A of Part 14 of Schedule 2 to the General Permitted Development Order 2015 in England. The DESNZ-commissioned safety study calls the position of plug-in PV here "currently unclear", and whether Class A reaches flats is contested. The planning permission position sets out both readings.
Plug-and-play solar. A marketing synonym for plug-in solar, used interchangeably with balcony solar, mini solar and plug-in panels. It carries no legal weight: the term UK law uses is plug-in microgenerator, and solar kits sold under these names face identical tests. Our complete guide to plug-in solar panels sticks to the plainer name.
Plug-in microgenerator. The statutory term, defined identically in regulations 2 and 3 of SI 2026 No. 848 as a source of energy which:
(a) generates electricity from the direct conversion of sunlight into electricity;
(b) has a maximum rated alternating current output not exceeding 800 watts;
(c) is intended for connection to a low voltage consumer’s installation by means of a standard plug and socket;
(d) is designed to operate in parallel with a distributor’s network; and
(e) is not designed to import electrical energy from a low voltage consumer’s installation for the purpose of storing energy for later supply, other than for control or auxiliary functions permitted by the Plug-in Solar Device Interim Product Specification.
Limb (e) is where the battery exclusion lives. The specification carries no clause prohibiting battery storage; it simply puts storage outside its scope. What shuts a grid-charging battery out of the route is the definition above, which is the distinction behind why battery kits are excluded and what changes on 27 August 2026.
PSSR 1994. The Plugs and Sockets etc. (Safety) Regulations 1994, SI 1994/1768. Regulation 2 of SI 2026 No. 848 inserted a new paragraph (3A) into its regulation 8, letting a notified body approve a plug type for a plug-in microgenerator despite the BS 1363 restriction, provided it conforms in every other respect and meets the specification. Unlike the ESQCR limb, this one extends to Northern Ireland. See the day the law changed.
R
RCBO. Residual current breaker with overcurrent protection: one device in the consumer unit combining residual current detection with overload and short-circuit protection. It matters because a circuit is defined by its protective device. Everything fed by a single MCB or RCBO is one circuit, and that’s what the one device per circuit rule counts. No dedicated circuit is needed; the device shares whichever socket circuit you plug it into.
Ring final circuit. The looped socket wiring used for standard 13 A socket-outlets in UK homes: one cable leaves a single protective device, runs through a series of socket-outlets and returns to the same terminals. Two current paths, one origin, one circuit. BS 7671 didn’t anticipate a generator injecting current into the middle of it, and how plug-in solar panels work explains what that does to the loading assumptions.
S
SEG (Smart Export Guarantee). The scheme obliging larger suppliers to pay for units you export to the grid. Eligibility detail sits in Schedule A to Standard Licence Condition 57 of the supply licence and in Ofgem’s guidance for generators. Where you can’t show suitable certification, Ofgem says a licensee "is not obliged to offer payments under the SEG, but they can make payments if they wish". Our SEG tariffs hub and current export rates cover the rest.
Self-consumption. The share of what you generate that gets used in the home rather than exported. It decides whether a kit pays for itself: a unit that runs an appliance in your own home is worth your full import rate, while an exported unit earns an export rate at best. If the point is to generate your own electricity and see it on the bill, this is the figure to watch. See our self-consumption and payback guide.
SI 2026 No. 848. The Plugs and Sockets etc. (Safety) Regulations 1994 and Electricity Safety, Quality and Continuity Regulations 2002 (Amendment) Regulations 2026. Made on 16 July, laid before Parliament the next day, in force on 27 August 2026. Regulation 1(3) extends regulations 1 and 2 to England and Wales, Scotland and Northern Ireland; regulation 1(4) extends regulation 3 to England and Wales and Scotland. The legalisation timeline orders every date.
String inverter. A single larger inverter taking the combined DC output of panels wired in series, which is how an ordinary rooftop system is built. One weak or shaded panel pulls the whole string’s operating point down, and a plug-in device has to present a small AC output at a plug, so balcony kits use microinverters. A rooftop solar installation faces neither constraint; inverter types compared covers both.
W
Wp, W and VA. Wp, or watt-peak, is a solar panel’s DC output under standardised laboratory test conditions, and it’s the label figure the 2,000 W DC cap is measured against. W is real power, the part that does work. VA is apparent power, and it’s what the specification caps at 800. None of them tells you how much solar energy a balcony will collect. What an 800 W kit will actually run turns the figures into appliances.
The numbers a compliant device has to hit
800 VA maximum AC output. 3.5 A maximum AC current. Single phase only. 2,000 W maximum DC panel capacity, up to four modules, no more than two in series, and open-circuit voltage at the inverter inputs not exceeding 120 V DC. Above 960 W of panels the manufacturer must advise a professional assessment of your wiring. That’s advice, not a limit, and crossing it isn’t a compliance failure. The compliance checker runs a kit against the lot.
Frequently asked questions about plug-in solar
What does "plug-in solar" mean in UK law?
The legal term is "plug-in microgenerator". SI 2026 No. 848 defines it in five limbs covering the energy source, an AC output not exceeding 800 watts, connection by a standard plug and socket, parallel operation with the network, and the exclusion of devices designed to import electricity to store it.
What’s the difference between the DNO and my energy supplier?
Your supplier sells you electricity and sends the bill. Your DNO owns the cables that deliver it and has no commercial relationship with you. Notification goes to the DNO. Whether you also tell your supplier is a separate question, covered in telling your electricity supplier about solar.
Does a plug-in solar device need an electrician?
A compliant device plugged into an existing socket isn’t notifiable electrical work, so DIY solar is the normal route. Adding or altering a circuit is notifiable, meaning professional installation or a building control notification, and the specification advises a professional assessment above 960 W of panels. Whether you need an electrician sets out where the line falls.
Why do some kits say 800 W and others say 800 VA?
Because the two governing documents chose different units and neither explains the other. Watts measure real power, volt-amps measure apparent power, and they’re equal only at a power factor of exactly 1. Size to the tighter of the two figures until somebody clarifies it.
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