Last reviewed: 3 September 2026. Every requirement quoted here is
taken from the DESNZ Plug-in Solar Device Interim Product Specification, version 2.0, July
2026. It is an interim document and will be superseded; we re-check this page when it is.
Disclosure: this is an article about products. Some retailer links on WattNest are
affiliate links and we may earn a commission if you buy through one — it never changes your price, and
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A compliant plug-in solar kit is four things: one to four panels, a microinverter rated at no more
than 800 VA, a manufacturer-supplied cable ending in a moulded 13 A plug, and a mounting system with a
structural analysis behind it. Everything else in the box is documentation — and the documentation is
not padding. The specification lists what it must contain, and the absence of any of it is the fastest
way to spot a kit that should not be on sale in Britain.
The four physical components
1. The panels
One, two or four panels of typically 400–500 W each. The specification puts hard numbers on this:
the combined DC rating of the modules may not exceed 2,000 W, no more than
four modules may be connected to the inverter, and no more than two may be wired in
series within any string. The open-circuit voltage arriving at the inverter input must not
exceed 120 V DC — a limit adopted specifically to reduce the risk of a sustained DC
arc, which is the failure mode nobody markets against.
There is also a threshold most buyers have never heard of. Above 960 W of total
panel capacity, the manufacturer is required to advise you to consider a professional assessment of
your existing electrical installation before fitting the kit. Two 500 W panels are over that line. It
is advice, not a prohibition — but if you are buying a two-panel kit, you have bought into that
recommendation whether the listing mentions it or not.
2. The microinverter
This is the regulated component and it does all the safety work. Its maximum apparent power output
must not exceed 800 VA and its maximum current must not exceed 3.5 A.
It must be type tested to Engineering Recommendation G98, and the manufacturer must have
registered the device on the ENA type test register and received confirmation of
assessment before placing it on the market. Submitting a device for registration does not count; the
specification says so explicitly.
When you pull the plug, the inverter must stop feeding the pins: it has to disconnect from the
mains within 100 milliseconds of losing the supply, and the voltage at accessible plug
pins must fall below 34 V within the same 100 milliseconds. Capacitors larger than
100 nF must discharge below 34 V within one second. Those three figures are the whole reason a
generator is allowed on a domestic plug at all. More in
microinverters explained.
3. The AC cable and plug
A BS 1363-1 plug, non-rewireable and moulded, fitted with a BS 1362 fuse of
no more than 5 A, with partially insulated pins so live parts cannot
be touched during insertion or withdrawal. The plug itself must be marked with the rated current, the
“read the instructions” symbol (ISO 7010-M002), a statement that only one device may be connected per
household circuit, and a warning that it must not be used with an extension cable, multi-way adaptor,
RCD adaptor or travel adaptor. Those adaptors are not discouraged; they are
not permitted. If your only outdoor socket is on an extension lead, you do not have a
socket for this kit — see
plug-in solar and extension leads.
4. The mounting system
A mounting system must be supplied as part of a complete kit, with a full component list and a
structural analysis demonstrating it can take UK wind and snow loads calculated to the Eurocodes and
their UK National Annexes. Arrangements relying solely on cable ties, rope, string, adhesive
tape, bungee cords or straps are not permitted. The manufacturer must state the maximum
permissible installation height above ground and the minimum clearance between panel and mounting
surface for ventilation. Any attachment method must be reversible and non-permanent.
The box contents, item by item, against the specification
This table is our own reading of the specification, arranged the way you would actually check a
delivery. It is the check we would run before the first fine day.
| Item | What the specification requires | How you check it in five minutes |
|---|---|---|
| PV module(s) | Max 2,000 W DC combined; max 4 modules; max 2 in series per string; ≤120 V open-circuit at the inverter; data sheet to BS EN IEC 61730-1 |
Add the module wattages on the labels. Find the data sheet in the box, not only online |
| Microinverter | ≤800 VA apparent power, ≤3.5 A; G98 type tested; registered on the ENA type test register; data sheet to BS EN 50524 |
Read the nameplate for VA (not just watts). Ask the seller for the type test registration |
| AC cable and plug | Moulded non-rewireable BS 1363-1 plug, BS 1362 fuse ≤5 A, partially insulated pins, marked per §8.2.3.2 |
Look for the moulded body, the printed markings near the plug, and the fuse rating |
| DC connectors | To BS EN 62852, supplied by the manufacturer, matching pairs from one product family; pre-assembled adaptors only |
Check both halves came in the box. Never mix brands of connector |
| Mounting system | Supplied with the kit, full component list, structural analysis, stated maximum installation height; ties/rope/tape/straps not permitted |
Count the brackets against the parts list. If the “mount” is a strap, reject the kit |
| Consumer unit label | A label to be affixed to the consumer unit in a clearly visible position, replaced if the unit is moved or changed |
It is a small sticker and it is easy to throw away with the packaging. Do not |
| Instructions | In English; must include DNO registration and deregistration obligations with a QR code to the process |
Find the QR code. Its absence is the clearest single sign of a non-compliant kit |
| Outdoor components | IP55 or better outdoors, including any outdoor socket; better than IP44 for indoor-only parts | IP rating is printed on the inverter. Check your outdoor socket too — it is not in the box |
The documentation is where the compliance actually lives
The specification devotes more pages to what must be written down than to the hardware, and the
required warnings tell you a great deal about the product’s real limits. A compliant kit’s instructions
must prominently state, among other things:
- that installation is not permitted on ACM, MCM or HPL cladding systems, timber
cladding systems or timber balconies, nor on buildings subject to external wall remediation works; - that the device is not intended to be connected to, operated with, or used in
conjunction with a battery energy storage system — see
can you add a battery to a plug-in solar kit; - that only one plug-in device of up to 800 VA may be installed per household
circuit, and that G98 currently restricts this to one per household; - that you should check your installation has modern residual current protection (RCBOs), and have
it inspected by a professional electrician if it is on older fuse protection; - that any work altering the final circuit — replacing the overcurrent protective device, for
example — is for a qualified electrician only, under BS 7671; - that you are responsible for permissions from the landlord, freeholder or managing agent, for
planning and listed building consent, for keeping escape routes clear, and for
checking the effect on your insurance before installation.
What is not in the box, and usually needs to be
- An outdoor socket rated IP55. If the inverter and plug live outside, the socket
must be IP55 or better. Fitting one is electrical work. - A longer cable. You may only use connection cables specified or approved by the
manufacturer, and you may not extend the run with an extension lead. Measure first. - Any bracket for your particular railing. “Mounting included” often means a
generic clamp. Steel, glass and masonry are three different jobs. - The DNO notification itself. The kit supplies the instructions and a QR code;
you make the notification, within 28 days of commissioning. See
how to fill in a G98 notification and
how to find your DNO. - An electrician, in the specific circumstances the specification lists —
a doubtful or damaged socket, an installation without RCBOs, panel capacity above 960 W, or any
change to the circuit. See
do I need an electrician.
One thing the specification does not cover
Value. Nothing above tells you whether the kit is worth buying, and the components that vary least
between a £300 kit and a £900 kit are the ones that generate the electricity. What you pay more for is
mounting quality, documentation, monitoring and a seller you could actually pursue. The criteria for
choosing between kits are on how to choose a plug-in solar kit, and
the money is on savings and payback.
Sources.
DESNZ, Plug-in Solar Device Interim Product Specification
v2.0, July 2026 (PDF) ·
SI
2026/848 (legislation.gov.uk) ·
DESNZ, plug-in solar consultation outcome ·
Energy Networks Association, find your network operator.
Editorial methodology.