Panel installation and wiring
Plug-In Solar Interim Product Specification: What UK Buyers Need to Know
From 27 August 2026, plug-in solar is legal in the UK under BS 7671 Amendment 4, but only if the kit meets the Interim Product Specification (IPS). The IPS is not just a marketing term: it defines precisely what a certified kit must include and how it must behave. Here is what you actually need to check before you buy.
Helpful video reference. The Plug-in Solar Channel’s investigation “UK Plug-In Solar Standard Is Here - But Who Wrote It?” covers this topic in plain terms. Worth watching alongside this page.
1. What the Interim Product Specification is
The IPS is a technical document developed by BSI (the British Standards Institution) under instruction from government, setting out the minimum safety and performance requirements that a plug-in solar kit must meet before it can legally be sold and used in a domestic setting in the UK. It covers the inverter, the panels, the connecting cable, any integrated battery, and the whole kit as a packaged unit. Importantly, it is a whole-system specification: individual components that carry CE or UKCA marks separately do not automatically qualify as IPS-compliant when assembled into a kit.
2. What a certified kit must include
An IPS-compliant plug-in solar kit must limit AC output to 800 W (or 800 VA, whichever is lower) at the socket. It must use a cable with an appropriate plug for a suitable socket circuit, it must not use an extension lead or adaptor, and the entire kit (inverter, panels, and cable) must be certified together as a single unit rather than as separate components. The inverter must also include active anti-islanding protection and must disconnect automatically if the supply voltage or frequency moves outside set limits. A kit that modifies any certified component, or combines parts from different certified kits, is no longer considered compliant.
3. Who wrote the IPS and why it matters
The IPS was fast-tracked through BSI at the direction of the Department for Energy Security and Net Zero (DESNZ), with input from industry groups including the Solar Energy UK trade body and several inverter manufacturers. The fast-track process (known as a Publicly Available Specification, or PAS) is used when a standard is needed before the full committee-based process can be completed, which is why some in the industry have raised questions about how the requirements were shaped and by whom. For buyers, the practical effect is that the document exists and manufacturers are certifying against it: a kit carrying IPS certification has been independently tested to those requirements, whatever the political debate around the process.
4. How to check if a kit is certified
A compliant kit should carry a statement that it meets the UK Plug-In Solar Interim Product Specification, along with a certificate number from a UKAS-accredited test house. Some manufacturers display this on the product label; others include it in the product documentation. At the time of writing, the list of certified kits is still relatively short: the market was anticipating the standard before it was finalised, and not all products that were being marketed as “pre-compliant” or “ready for legalisation” have completed the certification process. If a kit does not carry an IPS certificate with a traceable certificate number, it is not compliant, regardless of what the listing says.
5. G98 DNO notification still applies
A common misunderstanding is that an IPS-certified kit removes the need to notify the Distribution Network Operator. It does not. G98 notification to your DNO is still mandatory before you connect any plug-in solar kit to the grid, and must be submitted before the kit is energised, not after. G98 applies to systems up to 16 A per phase with no export battery: if your kit includes a battery that can export to the grid, you may need G99 approval instead, which takes considerably longer. The 800 W electrical limit on the kit has nothing to do with the DNO notification threshold.
Not all ‘legal plug-in solar’ claims are equal
From 27 August 2026, the BS 7671 Amendment 4 changes mean socket-connected plug-in solar is no longer prohibited by wiring regulations. But a kit being sold after that date is not automatically legal: it still needs to meet the IPS to be sold legally under product safety law. Check for an IPS certificate number before you buy, and verify it with the test house if you have any doubt.
Frequently Asked Questions
What is the Plug-In Solar Interim Product Specification?
The IPS is a UK technical standard that defines what a plug-in solar kit must include and how it must behave to be sold and used legally in a domestic setting from 27 August 2026. It covers the whole kit (inverter, panels, cable) rather than individual components.
What makes a plug-in solar kit IPS-compliant?
The kit must limit AC output to 800 W at the socket, use a cable plugged directly into a suitable socket (no extension leads or adaptors), include anti-islanding protection in the inverter, and be certified as a complete unit rather than as separate components. Any modification or mixing of parts from different certified kits invalidates the certification.
Do I still need to notify my DNO with a certified plug-in solar kit?
Yes. G98 notification to your Distribution Network Operator is still required before you energise any plug-in solar kit, certified or not. IPS certification confirms the kit meets product safety requirements; it does not replace the DNO notification obligation under the G98 or G99 engineering recommendations.