A garage conversion electrical package typically costs £1,500 to £4,500. This guide covers required circuits, heating load calculations, Building Regulations Part P notification, and consumer unit considerations.
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Written and reviewed by Andrew Moore, founder of Elec-Mate, against BS 7671:2018+A4:2026, IET Guidance Note 3 and the IET On-Site Guide.
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Converting a garage to a habitable room — home office, bedroom, gym, or playroom — is one of the most popular home improvement projects in the UK. The electrical work is a significant part of the conversion: a bare garage with a single light and perhaps one socket must become a properly wired, heated, and lit habitable room that complies with Building Regulations.
The electrical package for a garage conversion typically includes new circuits for lighting, sockets, and heating; cable installation through the new walls and floor; a consumer unit check and possible upgrade; smoke detector installation; and Part P notification. Testing and certification under BS 7671:2018+A4:2026 is required for all new circuits.
This guide covers typical costs, the circuits required, heating load calculations, Building Regulations requirements, and how to quote and certify garage conversion electrical work efficiently.
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The electrical cost for a single garage conversion (up to 20m²) typically falls in the following ranges:
These figures are for labour and materials combined. The main cost drivers are the distance between the garage and the house consumer unit, whether the consumer unit needs upgrading, the type and area of heating, and the number of circuits required.
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A habitable room converted from a garage requires the following electrical circuits as a minimum:
A dedicated lighting circuit or extension of the house lighting circuit. LED downlights or surface fittings. Consider PIR switching or a 2-way switch arrangement for convenience. Minimum 1 lighting point per 10m².
Ring final or radial socket circuit with at least 4 double sockets. For a home office, consider a second socket circuit for data and IT equipment. USB-A/C combination sockets add value.
Dedicated circuit for underfloor heating mat or electric radiators. Size the cable and MCB for the total heating load plus 20% margin. Include a programmer or smart thermostat on a switched fused spur.
In addition to circuits, the following are required under Building Regulations: an interlinked smoke alarm in the converted room (Grade D, LD2 as a minimum to BS 5839-6), and adequate ventilation provision (which may require an extractor fan circuit if the garage is used as a habitable bedroom).
Getting the heating load correct is critical for garage conversions because the starting point — an uninsulated concrete garage — has very poor thermal performance. The electrical heating load is directly determined by the insulation standard achieved.
Advise the homeowner that investing in proper insulation to Part L standard before installing the electrical heating reduces running costs substantially. Undersized heating (because the builder insulated well) is easy to correct; an oversized circuit installed before insulation decisions are made may be wasteful.
The cable sizing calculator allows the correct cable size and MCB rating to be confirmed once the heating load is known.
Professional quotes with the remedial estimator, then invoice from your phone the moment the work is done. From £6.99/mo.
Try the quoting tools freeA garage conversion requires Building Regulations approval in two areas relevant to electricians: Part P (electrical safety in dwellings) and the broader structural and thermal performance requirements that affect how the room is built.
The Part P certificate (issued by the competent person scheme after the EIC is submitted) must be provided to the homeowner. Without it, the garage conversion may be flagged as non-compliant if the property is sold or re-mortgaged.
Before quoting, assess the existing consumer unit for spare capacity and compliance:
Garage conversions are excellent recurring work — they come in clusters (neighbours talk) and the homeowner is usually committed to spending. A professional quote with clear scope and itemised costs wins the job. Key points for quoting:
Always survey the consumer unit before quoting. If an upgrade is likely, price it as an optional item — let the homeowner choose whether to include it now or defer it. This avoids pricing surprises on the day and demonstrates professionalism.
Always include the Part P notification fee (typically £40 to £80 via your competent person scheme) as a line item. Homeowners appreciate seeing it explicitly — it demonstrates that compliance is handled as part of the package.
Complete the Electrical Installation Certificate on site after testing. AI board scanning, voice test entry, and instant PDF export mean the certificate is ready before you leave. Submit directly to your competent person scheme from the app.
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