The BSI Product Standard for Plug-in Solar: What It Means and When It Lands

The BSI product standard is the final regulatory piece that makes plug-in solar legal to connect. It's expected July 2026. Until it's published and your kit has been tested against it, even with Amendment 4 done and government approval in place, connection is not permitted.

This guide explains what the BSI is, what the product standard does, what it will test for, and what to look for when it's published.

What Is the BSI?

The BSI (British Standards Institution) is the UK's national standards body. It develops and publishes standards for safety, quality, and interoperability across industries — from electrical safety to food production to engineering.

A BSI standard specifies how to do something safely or how a product should perform. For example:

• BS 1881 covers concrete testing
• BS 9440 covers window safety
• BS 7671 covers electrical installations (what we discussed earlier)

For plug-in solar, the BSI is developing a new standard specifically for small photovoltaic systems connected to low-voltage domestic networks. This standard is sometimes referred to as PAS 6161 (Publicly Available Specification) during development, or as BS [TBD] once formally published.

What's the Difference Between Amendment 4 and the Product Standard?

This is the critical distinction:

Amendment 4 (BS 7671) is the framework. It says: "Here's how to safely connect a small solar system to your home electricity." It covers wiring, earthing, circuit protection, etc. It's the process.

The BSI product standard is the list of approved products. It says: "This specific inverter has been tested and proven safe for small PV systems." It's the certification.

You need both. Amendment 4 without a product standard is like having building regulations for how to extend a house, but no way to certify that specific building materials are safe. The regulations tell you how to do it; the standard tells you what products are approved.

Why Is the BSI Standard So Important?

Until the BSI standard is published, no plug-in solar kit is legally connectable in the UK, even if it's technically safe and Amendment 4 is done.

Here's why: The regulations say "you can connect small PV systems safely this way" (Amendment 4). But they don't say which inverters, panels, and kits are safe. An inverter might be certified in Germany, but has it been tested against UK-specific requirements? Does it have UK-rated connectors? UK-standard documentation?

The BSI standard answers these questions by testing specific products and certifying them. Once certified, a kit gets UKCA marking (UK safety certification mark). Only UKCA-marked kits are legally connectable.

Without the product standard, there's no way to certify kits, so there are no UKCA-marked kits, so there's nothing legal to connect.

What Will the Product Standard Cover?

Based on the regulatory framework already in place in Germany and the EU (which has equivalent standards), the BSI product standard will test for:

Anti-islanding protection. If the grid fails, the inverter must automatically stop exporting power within a few seconds. Engineers working on power lines depend on this. The standard will specify maximum stopping time and test procedures to verify it works.

Maximum system size. The UK cap is 800W. The standard will test that inverters correctly identify system size and limit output accordingly.

Electrical safety. Connector types, cable gauges, earthing and bonding, protection against electric shock, etc. These must meet UK (and often EU) electrical safety standards.

DC side safety. The panel-to-inverter connection must be safe. Correct cables, correct connectors, proper insulation, protection against faults.

AC side safety. The inverter-to-socket connection must be safe. The three-pin UK plug and circuit protection must be correct.

Labelling and documentation. The kit must come with clear user instructions, safety warnings, electrical specifications, and certificates. Users must understand how to install and use it safely.

RCD compatibility. The inverter must work safely with the RCD (residual current device) on the household circuit that's powering it.

Environmental resistance. If the inverter is outdoors, it must resist rain, UV, temperature extremes, etc. The standard will specify required ratings (e.g., IP65 weatherproofing).

Performance and efficiency. The inverter must convert DC to AC with reasonable efficiency and accuracy. It shouldn't waste power or distort the grid.

What About Inverters That Are Already Legal Elsewhere?

A inverter legal in Germany might not be UKCA-marked. That's because UK requirements can differ from EU requirements (connectors, grounding approaches, documentation language, etc.).

Manufacturers can apply their existing certifications to the UK standard, and many will. But there will likely be UK-specific testing and certification. This is normal — every country does this.

Major brands (EcoFlow, Anker SOLIX) have confirmed they're preparing UK-compliant kits. They'll have tested and certified their products under the new standard. When July 2026 comes, their kits will arrive with UKCA markings proving they've passed the tests.

When Will It Be Published?

The BSI product standard is expected July 2026. This is not a firm date — standards can slip — but it's the current expectation. The BSI was already developing this standard before the March 2026 government announcement; the political decision accelerated publication.

Once published, manufacturers will begin certification testing. The first UKCA-marked kits should appear in shops within weeks or months of publication. By summer 2026 (July onwards), you should see them in Amazon, Lidl, Iceland, Sainsbury's, and specialist online retailers.

What to Look For When Buying

From July 2026 onwards, when you see plug-in solar kits for sale, look for:

UKCA marking. This will be a label on the packaging, manual, or inverter itself. It's a small logo (similar to the old CE mark). If there's no UKCA mark, the kit hasn't been certified and you cannot legally connect it.

Certificate or test report. The kit should come with or make available a test report showing it's been tested against the BSI product standard. Reputable manufacturers will provide this.

Clear documentation. The manual should be in English, clear, and include electrical specifications, installation instructions, and safety warnings. If the manual is vague or poorly translated, the kit probably isn't properly certified.

Reputable brand. Established manufacturers (EcoFlow, Anker, etc.) are more likely to have invested in proper certification. Cheap unknown brands from marketplace sellers might be uncertified or poorly certified.

Price point. A compliant kit will likely cost £400–£700. Significantly cheaper kits (£150–£200) are suspiciously cheap and may be uncertified or low-quality.

UKCA Marking Explained

UKCA stands for "UK Conformity Assessed." It's the UK's certification mark, equivalent to the EU's CE mark.

UKCA marking means a product has been:

• Tested against relevant UK standards (in this case, the BSI product standard)
• Proven to meet safety and performance requirements
• Certified by the manufacturer (or an approved testing body) as compliant

UKCA marking is a legal requirement for any electrical equipment sold in the UK. If you see an electrical device in a UK shop without UKCA marking, that's a red flag (unless it's very old, before UKCA existed, or imported and exempt).

For plug-in solar, UKCA marking will be your assurance that the kit has been properly tested.

What About Kits Currently for Sale?

From April 2026, you can already buy plug-in solar kits in some UK shops and online. Retailers like Amazon and Lidl are stocking them because the hardware is ready and demand is high.

These kits are not yet legally connectable. They don't have UKCA marking because the standard hasn't been published yet. When the BSI standard is published (July 2026), these kits will either:

• Be tested and certified (at which point they'll be rebranded as UKCA-marked)
• Fail certification (at which point they'll be withdrawn or redesigned)
• Be untested (at which point they'll remain on shelves but can't legally be connected)

You can buy and mount an uncertified kit now if you want. But don't connect it until you're sure it bears UKCA marking (which won't happen until the standard is published and testing is complete).

This is a weird grey zone: retailers selling products that you can't legally use yet. It exists because shops are preparing for summer 2026 when compliant kits will definitely be needed.

Enforcement

Once the product standard is published, enforcement will gradually tighten. Early on (summer 2026), most people will be allowed to self-certify compliance. But over time:

• Local authorities may require notification of solar installations and proof of compliance
• Insurers may ask to see UKCA certificates
• Grid inspectors might spot-check systems
• Surveyors selling properties may ask for certification

It's not harsh, but it's real. The smart move is to follow the rules from day one: use UKCA-marked kits, keep the certification, and notify your DNO.

The Official Announcement

When the BSI product standard is officially published (July 2026), it will be announced on the BSI website. Major news outlets will cover it. We'll update this page and our complete legal guide with the exact standard number and any specific requirements.

You can also check the BSI website directly: www.bsigroup.com

The Bottom Line

The BSI product standard is the final legal gate. Without it, no kit can be certified and no kit can be legally connected. With it (July 2026), UKCA-marked kits will appear in shops and you can legally buy, install, and connect them.

Until July 2026, you can prepare: research kits, check your balcony or garden for suitability, calculate your potential savings using our calculator, and get landlord permission if you rent.

When July comes and the standard is published, you'll know exactly what to look for. UKCA marking = legally compliant. No UKCA marking = not legally connectable. It's that simple.

For the full legal timeline and what happens at each stage, see our complete legal guide.