Plug-in Solar Terms Explained: G98, SEG, MCS and More

What SI 2026/848, the Interim Product Specification, G98, G99, DNO, SEG, MCS, kWp and self-consumption actually mean for a UK plug-in solar kit.

Close-up of photovoltaic solar panel cells
Updated
By Rob Griffiths8 August 2026 · 6 min read

Plug-in solar carries an unusual amount of jargon for a product you are meant to be able to plug in. Some of it is legal, some is grid engineering and some is money, and the three are easy to confuse. Here is what each term means, and which ones actually affect what you can buy and use.

What do the legal terms mean?

SI 2026/848 is the statutory instrument that makes plug-in solar legal in the UK. Its full title is the Plugs and Sockets etc. (Safety) Regulations 1994 and Electricity Safety, Quality and Continuity Regulations 2002 (Amendment) Regulations 2026. It was made on 16 July 2026 and comes into force on 27 August 2026.

Plug-in microgenerator is the legal category the regulations create, and the definition is tighter than most coverage suggests. It is a device that generates electricity by direct solar conversion, has a maximum rated AC output not exceeding 800 watts, is intended to connect through a standard plug and socket, is designed to operate in parallel with the network, and cannot import energy for storage beyond auxiliary functions. That last clause is why a kit with a battery in it falls outside the category.

Interim Product Specification (IPS) is the document a compliant kit must be certified against. Version 2 was published by the Secretary of State on 16 July 2026, the same day the regulations were made, and the regulations give it legal force. This is the thing people mean when they say a kit must be 'certified'.

BS 1363 is the British Standard for plugs and sockets, which normally prohibits feeding power into a socket. The regulations work by creating an exception to it: a plug that does not fully conform to BS 1363 is permitted when it complies with the Interim Product Specification instead.

What do the grid-connection terms mean?

DNO is your Distribution Network Operator, the company that owns the physical cables in your area. It is not your electricity supplier, and you do not choose it: it is determined by where you live. The DNO is who you notify when you connect generation.

G98 is the Energy Networks Association engineering recommendation covering small generation connections, and it works on a connect-and-notify basis: you install, then tell your DNO, rather than waiting for permission. It applies up to 16 amps per phase, which is roughly 3.68 kW on a normal single-phase home supply. A plug-in kit is far below that ceiling, and G98 still applies to it after 27 August 2026.

G99 is the equivalent for anything above the G98 threshold, and it is a different proposition: a full application with DNO approval BEFORE connection, rather than a notification afterwards. Relevant if you later add a full roof array, not for a plug-in kit.

What do the money terms mean?

SEG is the Smart Export Guarantee, the scheme under which licensed electricity suppliers pay small-scale generators for electricity exported to the grid. Ofgem reports that it launched on 1 January 2020, covers installations up to 5 MW (50 kW for micro-CHP) in Great Britain, and that tariff rates must always be above zero. Payment is based on export meter readings, so an export-capable smart meter is the practical prerequisite.

MCS is the Microgeneration Certification Scheme, which certifies installers and products. Suppliers generally want evidence that an installation is eligible before paying SEG, and an MCS certificate is the usual form that evidence takes, which is why the two are so often mentioned together. Worth checking your chosen supplier's own stated requirements rather than assuming, because they set their own terms.

Self-consumption is the share of what you generate that you use in the house rather than export. It matters more than export payments for a small kit: electricity you use offsets the full unit rate you would otherwise pay, while exported units earn whatever the export tariff is, which is usually much less.

What do the hardware terms mean?

Microinverter is an inverter that sits behind an individual panel rather than serving a whole array, converting that panel's DC output to mains AC on the spot. Plug-in kits use them because the output has to be AC by the time it reaches the plug.

kWp means kilowatt peak: a panel's rated output under standard test conditions, not what it produces on a normal day. It is a comparison figure between panels, not a forecast of your generation.

RCD is a residual current device, the protective device in a consumer unit that disconnects a circuit on detecting an earth fault. It comes up in plug-in solar discussions because the circuit you plug into should be RCD-protected, as modern UK sockets normally are.

What is a plug-in microgenerator in law?
A device defined by SI 2026/848 that generates electricity by direct solar conversion, has a maximum rated AC output not exceeding 800 watts, connects through a standard plug and socket, operates in parallel with the network, and cannot import energy for storage beyond auxiliary functions. The storage clause is why battery-integrated kits sit outside the category.
What does it mean for a plug-in solar kit to be 'certified'?
Certified against the Plug-in Solar Device Interim Product Specification version 2, published by the Secretary of State on 16 July 2026. The regulations give that specification legal force and allow a plug meeting it to be used where BS 1363 would otherwise prohibit feeding power into a socket.
Do I still need to tell my DNO after 27 August 2026?
Yes. The connection still falls under G98, which is connect-and-notify: you install and then notify your Distribution Network Operator, rather than seeking approval first. The legalisation removes the need for an electrician to wire it in; it does not remove the notification.
What is the difference between G98 and G99?
The threshold is 16 amps per phase, roughly 3.68 kW on a single-phase home supply. At or below it, G98 applies and you notify after connecting. Above it, G99 applies and you need a full application approved by the DNO before connecting. A plug-in kit is far below the G98 ceiling.
Can I get SEG payments for a plug-in kit?
SEG is the scheme suppliers pay export under, and Ofgem's criteria cover installations up to 5 MW in Great Britain with payment based on export meter readings. Whether a supplier will accept a plug-in kit is a question for that supplier, since they set their own evidence requirements and most are built around MCS-certified installations. For a kit this small, self-consumption is where the value is anyway.
Is PAS certification relevant to plug-in solar?
Not for the legal question. The standard that decides whether a plug-in kit is compliant is the government's Interim Product Specification version 2, referenced directly by SI 2026/848.

Where to read more

Each of these terms has a page behind it on this site: