Glossary
Interim Product Specification
The DESNZ rules a plug-in solar kit must meet before it can legally be installed and used in Great Britain.
The Plug-in Solar Device Interim Product Specification (version 2, published by DESNZ on 16 July 2026) is the technical standard behind the GB plug-in solar law. Under the amended electricity safety regulations, a plug-in microgenerator must comply with this specification rather than the usual British Standard requirements (ESQCR reg 22(1)(c); SI 2026/848).
Its main rules for buyers (IPS):
- Output no more than 800 VA and 3.5 A; panels no more than 2,000 W DC.
- A moulded BS 1363-1 plug with a fuse of 5 A or less, plugged directly into a fixed socket. No extension leads or adaptors.
- Outdoor sockets and components rated at least IP55.
- No batteries.
- Not on timber balconies, timber cladding, ACM, MCM or HPL cladding, or buildings under external wall remediation.
- Mounting must be reversible and non-permanent.
- Listed as Compliant on the ENA Type Test Register.
It is “interim” because a full revision of the underlying British Standards is planned within around two to three years (Explanatory Memorandum, para 6.5).