An electrically charged heat battery can be one of the largest loads in a home. The installer must assess the complete supply rather than finding an empty way in the consumer unit.
The short answer
Check the unit's maximum current, supply phase, charge duration, required protective devices and other large loads. A dedicated circuit may be needed, and some homes require load management or work upstream of the consumer unit.
Maximum demand
Electric showers, EV chargers, ovens, heat pumps and battery storage can overlap. The design should consider realistic coincidence and any control that prevents the main supply being overloaded.
Consumer unit and cable route
Spare physical space does not prove electrical capacity. Ask who designs the circuit, how the cable reaches the unit and whether walls, floors or fire-stopping need work.
Notification and certification
Electrical safety rules differ across the UK. In England, Approved Document P explains when work in dwellings is notifiable. The installer should identify the route that applies and provide the correct electrical certificate.
Smart load control
Controls can pause charging when another high-power appliance runs. Ask what happens if the controller loses communication and whether the store will still be ready by the end of the cheap window.
Supply upgrade timing
If the incoming service, meter equipment or network connection needs work, responsibilities and lead times may sit outside the heat-battery quote.
Your next step
Photograph the meter, main fuse area and consumer unit labels without removing covers. Give the electrician a list of EV, solar, heat-pump and shower equipment already installed or planned.
Sources
Primary and independent references checked by our editorial team.
- Electrical safety: Approved Document P — GOV.UK Checked 10 Nov 2026