Electric Boiler Installation in the UK – Electrical Requirements and Safety Guide
What Is an Electric Boiler?
An electric boiler heats water using electrical elements rather than gas. It is commonly installed
in flats, properties without gas supply, or homes seeking low-carbon alternatives.
While mechanically simpler than gas systems, electric boilers demand significant electrical capacity.
This is why installation must always be assessed by a qualified
Electrician in London.
Electrical Requirements for Electric Boiler Installation
Electric boilers typically range between 6kW and 15kW for domestic properties.
This translates to a high current draw, often between 25 and 65 amps depending on the model.
The electrician must assess:
- Total property load demand
- Main supply capacity (60A, 80A or 100A service fuse)
- Consumer unit spare ways
- Earthing and bonding adequacy
Cable Size and Amps Calculation
Correct cable sizing is critical. Undersized cables will overheat and create fire risk.
Depending on the boiler’s rating and installation method, cable sizes may include:
- 6mm² for smaller units (subject to calculation)
- 10mm² for higher demand boilers
- 16mm² in some larger installations
Professional London Electricians
perform full load calculations in accordance with BS 7671 regulations before installation.
Dedicated Circuit and Consumer Unit Capacity
Electric boilers require a dedicated radial circuit directly from the consumer unit.
This circuit is protected by a correctly rated MCB or RCBO.
In many cases, older consumer units may not have sufficient capacity.
Upgrading to a modern board with RCBO and SPD protection may be recommended.
During property checks such as
London Landlord EICR Certificates,
supply limitations are often identified before boiler upgrades proceed.
Common Electric Boiler Installation Mistakes
- Connecting to undersized cable
- Ignoring main supply limitations
- Overloading an existing circuit
- Failing to upgrade protective devices
- Poor termination causing overheating
These issues can lead to nuisance tripping, cable heating or dangerous electrical faults.
Compliance, Testing and Certification
Electric boiler installation must comply with the 18th Edition wiring regulations.
After installation, testing and certification are required.
- Continuity testing
- Insulation resistance testing
- Earth fault loop impedance testing
- RCD/RCBO trip time verification
Proper certification ensures insurance compliance and long-term safety.
When to Call an Emergency Electrician
If your electric boiler causes breaker tripping, burning smells or cable overheating,
contact London Emergency Electricians immediately.
High-load appliances like boilers must never be left operating on a faulty circuit.
Final Advice
Electric boiler installation is not a simple plug-in job. It requires careful calculation
of cable size, current demand and supply capacity.
Always use a qualified electrician to ensure your installation is safe, compliant and built for long-term reliability.