Wieland Connectors and Plug-In Solar: Germany's Plug and the UK Rules

In balcony solar, a “Wieland connector” means the RST circular connector made by Wieland Electric of Bamberg, Germany. On a German kit it’s a latching plug that goes into a matching socket an electrician fixes in place, used instead of an ordinary Schuko wall socket. A UK kit can’t use one at the wall. The UK specification requires a factory-fitted BS 1363 plug, and it bans the adaptors that might look like a way round that.

What a Wieland connector is

Wieland Electric’s balcony solar page says: “Our RST® circular connectors have been specially designed for efficient, pluggable and IP-protected electrical installation”. Its RST CLASSIC flyer describes the socket as being “For the standard compliant connection of power generation equipment up to 2000W” and “designed for the pluggable feed-in of energy from so-called ‘balcony power plants’”.

• Locking: “Automatic, mechanical locking of the RST® CLASSIC connectors during mating”.
• Touch protection: “Touch-proof contacts with male and female connectors, even in un-plugged state”.
• Parts: the flyer lists the RST20i3 range, a 3-pole, 250 V, 20 A device connection, with a matching plug and mounting frame.
• Standard: Wieland calls it its “IEC 61535 certified RST connector system”. IEC 61535 covers installation couplers, and the UK specification refers to it too.
• Fitting: Wieland is firm that the socket is electrician’s work: “This assembly must not be carried out by private persons under any circumstances.”

Wieland says RST has been “the quasi-standard interface” for string inverter makers since the early 2000s. You’ll also see Wieland’s GST18 name attached to balcony kits, but Wieland’s own balcony solar page and flyer name RST.

Why Germany used it

Germany’s installation standard for plug-in generation, DIN VDE V 0100-551-1, was revised in 2016 to cover feeding power into household sockets. The VDE explains that “Along with a fixed connection, the standard requires a special energy socket for this purpose.”

The standard never named a brand. The DKE’s interpretation note says the special energy socket was deliberately left undefined to stay technology-neutral (“Um technologieoffen zu bleiben”). A companion standard, DIN VDE V 0628-1, defines an energy connector as a hand-releasable latching connector made up of a socket and a plug. So “Wieland plug” was the market’s shorthand for one product that met the rule, and the rule itself named no maker. The IET’s position paper uses it: “Historically, Germany required connection via a specialist ‘Wieland’ plug, designed to prevent electric shock by avoiding exposed live pins, although this required professional installation.”

Alongside that, VDE-AR-N 4105, the VDE’s application rule for generating plants on the low-voltage network, let plug-in systems with up to 600 VA of inverter output be commissioned without an electrical contractor, according to VDE FNN. In January 2023 the VDE moved towards household plugs: Wieland quotes its position paper as saying “the VDE is in favor of tolerating the Schuko® Connector for feed-in up to a total system power limit of 800 W.”

What changed in Germany

Germany’s Solarpaket I is often said to have legalised Schuko plugs. It didn’t. The change took effect on 16 May 2024 and covered registration and the power limits for plug-in systems of up to 2 kW installed and 800 VA of inverter output. Registration with the grid operator was dropped, and registration in the Marktstammdatenregister stayed. VDE FNN’s own page, written after Solarpaket I, says connection was still only permitted through a special energy socket or a fixed connection, and that further solutions for household sockets would come with the product standard DIN VDE V 0126-95. Its second draft raised the feed-in limit from 600 VA to 800 VA and agreed protective measures for a household plug, the VDE said in May 2024.

The household plug arrived with DIN VDE V 0126-95, dated December 2025. The DKE’s FAQ, published 17 December 2025, lists three newly permitted options:

• a modified household plug with protective shrouding on the contacts
• a modified household plug with an internal disconnect switch
• a household plug combined with isolation and safe separation in the inverter

The special energy plug required until then stays permitted. The limits differ by connector. The inverter may feed in at most 800 VA either way, but module power is capped at 960 W with a household plug and 2,000 W with a special energy plug, on condition that an electrician installs the special socket. That’s where the “up to 2000W” on Wieland’s flyer comes from. Germany also bars multi-way sockets for these devices.

This matters in the UK because the UK specification names DIN VDE V 0126-95:2025-12 as “the primary technical and safety reference case”. One difference is the panel limit. Germany ties it to the plug, and the UK has a single 2,000 W cap, with makers required to advise a professional check of your wiring above 960 W. Our German kits guide compares the two in full.

What the UK requires instead

Neither “Wieland” nor “Schuko” appears anywhere in the Interim Product Specification v2. It doesn’t ban either by name. It sets out what the plug must be, and no Wieland or Schuko plug meets that.

• A factory-fitted UK plug. A plug-in solar device has “a factory assembled connection line fitted by the manufacturer with a plug designed to BS 1363”, and connects to a UK socket “solely by the manufacturer-supplied standard plug.”
• Clause 6.2.3.2, the plug itself. It must be designed to BS 1363-1, with partially insulated pins, and be a non-rewireable moulded plug with a BS 1362 fuse of no more than 5 A. The socket must comply with BS 1363-2. On top of that there has to be a second layer of contact protection, either mechanical (a locking mechanism, covers or shutters) or electromechanical, removing dangerous voltages from the contacts within 2 seconds of disconnection.
• Clause 6.2.3.1, no adaptors. “The use of multi-way adaptors, travel adaptors, RCD adaptors and plug convertors shall not be permitted.” Version 2 added RCD adaptors to the list. The ban is repeated in the on-plug warning and the instructions, along with extension leads.
• Disconnection. Once the plug is pulled, the inverter must keep hazardous voltages off the pins. It must disconnect automatically within 100 ms, and the voltage at the pins must drop below 34 V within 100 ms, a requirement the specification says is taken from DIN VDE V 0126-95.

A connector at the inverter end is allowed. Clause 6.2.3.1 permits detachable AC connector systems between the inverter and the connecting cable, as long as they have an ingress rating equivalent to the inverter’s, are labelled, and match any mechanical interlocking used elsewhere. When engaged outdoors they must give at least IP4XD, and IP2XB when unplugged. On our reading, an RST-style coupler on the inverter, feeding the maker’s own BS 1363 lead, fits those clauses. The specification names no brand.

The law attaches through SI 2026 No. 848, in force since 27 August 2026. It amends the Electricity Safety, Quality and Continuity Regulations so that a plug-in microgenerator must comply with the specification. There’s no UK version of Germany’s hard-wired energy socket either. The plug-in route is a BS 1363-2 socket only, at up to 800 VA, and the specification excludes “PV systems according to BS 7671 Section 712”, which are conventional installations. Our BS 7671 Amendment 4 guide covers how the Wiring Regulations fit in.

Buying a kit: don’t adapt an EU kit

• An adaptor doesn’t make it compliant. A kit with a Wieland or Schuko plug at the wall end fails clause 6.2.3.1 the moment you add a travel adaptor or convertor. Electrical Safety First agrees: “Plug-in solar systems should not be connected via extension leads, cable reels, multiway adaptors, travel adaptors or plug-in RCD adaptors.”
• Nor does a new plug or lead. The plug must be moulded on and fitted by the manufacturer, and the instructions must say that “only connection cables specified or approved by the manufacturer may be used”. The disconnection and contact-protection tests cover the whole device, so a lead from another brand, or one you wire yourself, leaves you with an untested combination.
• German or CE certification isn’t the UK test. The specification says it’s equivalent to DIN VDE V 0126-95 in most technical areas, “but where they differ this specification takes priority”. What counts here is the compliance declaration on the product and a verified listing on the ENA register.
• Check the plug against the documents. We’ve seen a UK listing whose product documents described a Schuko cable while its category page said UK 13A plug. Look at the photos and the manual, and ask the seller if they disagree.

The simple route is a kit sold for the UK with a BS 1363 plug already on it and a verified register listing. Our certified kit tracker lists them, how to tell a kit is legal walks through the checks, and if you’ve already bought one with a European plug, already bought a kit? sets out your options.

Frequently asked questions