Last reviewed: 6 September 2026. This page explains what a
compliant plug-in kit assumes about the circuit it is plugged into, and how to tell whether your house
meets those assumptions. It is general information, not an electrical inspection. Anything that
involves opening a socket, a consumer unit or a fixed circuit is work for a competent electrician.
A compliant plug-in solar kit is designed to be safe in a normal, sound British domestic
installation. That is the sentence to hold on to, because both halves matter. The design work has been
done — the requirements in the interim
product specification exist precisely so that a householder can plug one in without an
electrician. But every one of those protections assumes the socket at the other end is in good order
and connected to a circuit that behaves the way modern circuits behave.
In a house wired in 1968 and never touched since, that assumption is worth checking. Not because
plug-in solar is dangerous in an old house, but because an old installation with a hidden fault was
already the problem, and the panel simply becomes the reason you finally looked.
What the kit already protects against
| Requirement | What it prevents |
|---|---|
| Voltage at the plug pins falls below 34 V within 100 ms of unplugging (cl. 6.2.3.3.3) | Live pins in your hand when you pull the plug out mid-generation |
| Non-rewireable BS 1363-1 plug with a BS 1362 fuse of 5 A or less (cl. 6.2.3.2) | A fault current larger than the flex can carry, and amateur re-terminations |
| Maximum 800 VA AC output, 3.5 A (cl. 4.1) | A back-feed large enough to matter to a 13 A socket circuit |
| Residual DC current of 5 mA or less (cl. 5.7) | DC leakage that could blind an ordinary AC-sensing RCD |
| Loss-of-mains disconnection under G98 | The inverter energising a circuit that someone believes is dead |
The fourth row is the one that quietly matters most in an older house, and it is the reason the
5 mA figure is in the specification at all: a DC residual leaking into the installation can stop
an RCD from tripping when it should. The specification caps it so that whatever protective device your
house has, the inverter does not degrade it.
The checks worth doing before you buy
None of these require tools, and none of them involve removing anything.
1. Look at the consumer unit
A modern board has a row of breakers and at least one RCD or a set of RCBOs, usually with a test
button. An old board has ceramic fuse carriers you pull out, or a row of small breakers and no test
button anywhere. Rewireable fuses are not a reason to panic and they are not illegal, but they tell you
the installation predates several revisions of the wiring regulations, and they mean there is no
residual current protection on that circuit at all.
2. Look at the socket you intend to use
Scorch marks, a brown halo around a pin, a cracked faceplate, a plug that falls out under its own
weight, or a socket that gets warm with a kettle plugged in — any of those is a reason to have
that socket replaced before you use it for anything, let alone something that will sit there generating
for six hours a day in summer. A loose connection heats up in proportion to how long current flows, and
solar makes that duration much longer than a kettle does.
3. Ask when the installation was last inspected
An Electrical Installation Condition Report is the actual answer to “is my wiring all right”, and the
only one. If your house has never had one, or the last one is more than ten years old, that is the job
to book — not because of the panel, but because you are about to find out either way. Landlords
in England already have to hold a valid EICR for rented properties.
4. Find out whether the outdoor socket is protected
If you plan to plug into an outdoor or garage socket, it should be RCD protected and rated for the
location. Adding one is a job for an electrician and, in England and Wales, may be notifiable work
under Part P of the Building Regulations.
The wiring conditions that actually matter
| What you find | Does it stop you? | What to do |
|---|---|---|
| No RCD anywhere in the house | Not a legal barrier, but the weakest case | Get an EICR and price an RCD upgrade. You wanted this anyway |
| Rubber or fabric-insulated cable (typically pre-1960s) | Stop and get it inspected | Perished insulation is a genuine hazard on its own terms, panel or no panel |
| A ring final circuit in good order | No | This is the normal British case and what the kit assumes |
| An extension lead, adaptor or multi-way block in the plan | Yes, absolutely | Prohibited by the specification. See why extension leads are out |
| A spur of unknown provenance, DIY sockets, or a socket added by a previous owner | Not necessarily, but it is an unknown | Have it checked before you use it as a generation point |
| Aluminium conductors, or a shared neutral you have heard about | Get advice | Unusual in UK domestic work; treat any oddity as a reason for a professional look |
Why an old circuit is not overloaded by 800 W
The arithmetic is worth stating plainly, because the fear is common and misplaced. A compliant kit
injects at most 3.5 A into a circuit designed for 32 A on a ring final. It is a small contribution
relative to a kettle, and it flows only while the sun is up. The specification’s own limit of one
device per final circuit — and the tighter G98 rule of one device per home,
which prevails — exists so that this stays true. See whether you can have two kits.
The risk in an old house is not capacity. It is a poor connection somewhere that has been getting
slightly warm for twenty years without anyone noticing.
Where an electrician is genuinely required
A compliant kit needs none for its own installation. You need one if you want a new outdoor socket,
if you want RCD protection added, if the EICR comes back with anything coded C1 or C2, if you are
adding a battery — batteries are not part of a plug-in kit at all and are fixed electrical work
— or if you simply want somebody competent to look at a socket that worries you.
The wider framing is in do you need an
electrician. The short version: the kit is designed so the answer is no, and the house is where the
answer can become yes.
Frequently asked questions
My fuse box has ceramic fuses. Can I still use plug-in solar?
There is no rule against it. There is also no residual current protection on that circuit, which is
a good reason to get the installation inspected and to think about an upgrade. Do not let a panel be
the thing that makes you accept an installation you would otherwise have improved.
Will the panel trip my RCD?
It should not. A compliant kit limits residual DC to 5 mA precisely so it does not interfere with
RCD operation. If plugging it in trips an RCD repeatedly, unplug it and get both the kit and the
circuit looked at — something is wrong, and it may not be the kit.
Does the wiring have to be checked before I notify my DNO?
No. The G98 notification is about the generating device and the network connection, not about your
internal wiring, and it is a notification rather than an approval. It is still due within 28 days.
Is it safer to plug into a kitchen socket or an outdoor one?
Whichever is sound, dry, correctly rated for its location and reachable without a lead. A good indoor
socket beats a questionable outdoor one every time.
Sources.
DESNZ interim product specification (clauses 4.1, 5.7,
6.2.3.2, 6.2.3.3.3) ·
SI
2026/848 ·
Approved Document P (England and Wales; Scotland and
Northern Ireland have their own building standards).
Assessments of what older installations imply are our own and are labelled as such — see editorial methodology.