Part P Building Regulations and Solar Panels: What You Need to Know

If you are researching solar panels, you will have encountered references to Part P of the Building Regulations and wondered what it actually covers. The confusion is understandable — solar installations involve both physical roofwork and electrical work, and the regulations treat these very differently. This article explains exactly what Part P requires, when it applies, and what your options are whether you use a professional installer or take the DIY route.

What is Part P?

Part P is a section of the Building Regulations for England. It covers electrical safety in dwellings — meaning homes, flats, and outbuildings used in connection with a dwelling. The core requirement is that domestic electrical work is carried out competently, with that competence demonstrated in one of two ways: self-certification through a Competent Person Scheme (CPS), or inspection by an independent Building Control Body (BCB).

Part P came into force in 2005 following a period of concern about poor-quality DIY electrical work causing fires and accidents. It is distinct from planning permission (which governs whether you can install solar at all) and from MCS certification (which governs eligibility for export payments). You can have a fully Part P-compliant installation that is not MCS-certified, and vice versa.

What triggers Part P for solar?

The key trigger is connecting to the mains supply. For a solar or battery installation, this means:

• Connecting the inverter's AC output to the consumer unit (fusebox)
• Installing a new circuit or significantly altering an existing one within the dwelling
• Any electrical work within a special location such as a bathroom, if the installation runs near one

What does not trigger Part P:

• Physically mounting panels on your roof or a ground-mount frame
• Running DC cables from the panels down to the inverter location
• Connecting panels together using MC4 connectors (DC side only)
• Fitting optimisers or microinverters on the DC side of the system
• Installing mounting hardware: rails, brackets, roof hooks

This distinction matters enormously for anyone considering a DIY installation. You can legally carry out the roof work, the DC wiring, and all the physical installation yourself. It is only the moment you connect to your consumer unit that Part P applies.

Route 1: Professional installer with CPS self-certification

This is the standard route for the vast majority of solar installations in the UK.

Members of a government-authorised Competent Person Scheme — including NICEIC, NAPIT, ELECSA, and several others — are permitted to self-certify their own electrical work. Instead of requiring a separate Building Control inspection, the CPS operator notifies Building Control on the installer's behalf after the work is complete. You receive an Electrical Installation Certificate (EIC) as proof of compliance.

If you use an MCS-certified installer who is also CPS-registered (which is standard practice in the UK solar industry), compliance is handled as part of the installation package. There is nothing additional you need to apply for or arrange — the installer's certificate covers it.

One important change to be aware of: before September 2021, there was a lower-qualification "domestic installer" category within CPS schemes. This route was abolished in September 2021. All CPS scheme members now require full electrical qualifications. There is no lightweight or simplified self-certification path for the mains connection.

Route 2: DIY with a Building Control Body inspection

If the person carrying out the AC connection is not a CPS member — which includes most competent DIYers — the process is:

1. Submit a Building Regulations application to your local Building Control Body before work begins. Do not make the connection and then apply retrospectively.
2. Pay the inspection fee, which typically falls in the range of £200–400 depending on your local authority.
3. Carry out the work to the standard required by BS 7671 (the IET Wiring Regulations).
4. BCB inspects on completion and issues a completion certificate if satisfied.

This is the only legal route for a DIY mains connection, unless you take the hybrid approach described below. Carrying out notifiable work without following Part P is a criminal offence under the Building Act 1984 — and the practical consequences when you come to sell the property can be severe.

What about battery storage?

Battery systems are subject to the same Part P framework as panels. If a battery connects to your consumer unit — which all grid-connected home batteries do — that connection is notifiable work and requires either CPS self-certification or a BCB inspection.

There is an additional technical layer for batteries. BS 7671 Amendment 4, in force from 15 April 2026, introduces Chapter 57 specifically covering stationary secondary battery installations. This sets wiring requirements for battery systems that go beyond the general domestic installation rules. Any electrician carrying out battery connection work from April 2026 onwards should be familiar with Chapter 57.

Separately, battery location and fire safety requirements are governed by PAS 63100:2024, which is a different document to Part P — but both apply. If you are planning a battery installation, it is worth reading the battery fire safety guidance alongside this.

What certificate do you get?

Depending on the route taken, you will receive one of two documents:

• Electrical Installation Certificate (EIC): Issued by the CPS-registered electrician or installer. This is the standard document for professionally installed systems.
• Building Control completion certificate: Issued by the BCB after inspection under Route 2.

Keep whichever you receive. It is a key document when selling your property — conveyancers and mortgage lenders will ask for evidence that notifiable electrical work was certified. An installation without a certificate is a common cause of delays or renegotiation during property sales. Some insurers may also ask for it.

A note on Scotland and Wales

Part P applies specifically to England. Scotland operates under the Scottish Building Standards, which have their own electrical safety requirements that broadly follow similar principles but are administered differently. Wales follows the same Building Regulations as England, including Part P. Northern Ireland operates under its own Building Regulations (Part P applies there too, under the Building Regulations (Northern Ireland) 2012). If you are in Scotland, check the requirements under Scottish Building Standards rather than Part P.

Where to go next

For the full picture on what DIY solar involves legally and practically, Can I install solar panels myself? covers the scope of what you can and cannot do without qualification. The DIY solar complete guide pulls together all the practical resources for a self-install project. If you are weighing up costs and whether MCS certification is worth pursuing, Microgeneration Certification Scheme explains what MCS covers and when it matters.

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