What Happens If My Main Fuse Is Too Small for an EV Charger?
When installing an EV charger, one of the most important checks is the rating of your main incoming fuse.
Many UK homes have a 60A, 80A or 100A main fuse. If the fuse is too small relative to the total household demand, installing a 7kW EV charger can create supply limitations.
If you are considering installation, you can find full details of our EV Charger Installation services in Altrincham.
Why the Main Fuse Rating Matters
A standard 7kW EV charger typically draws around 32 amps.
If your property has a 60A main fuse and other high-demand appliances are operating at the same time — such as:
- Electric shower
- Oven or hob
- Heat pump
- Immersion heater
The total load may approach or exceed the supply capacity.
What Can Happen If the Supply Is Overloaded?
- Main fuse failure
- Nuisance tripping
- Overheating of supply components
- Potential damage to network equipment
This is why supply assessment is mandatory before EV installation.
How Is This Assessed?
A qualified installer will:
- Check the main fuse rating
- Calculate maximum demand
- Assess diversity across existing circuits
- Determine whether load management is required
This forms part of compliance with BS 7671 Wiring Regulations (Section 722).
What Are the Solutions?
1. Load Balancing
Dynamic load management monitors total household demand and reduces EV charging current when required. This often avoids the need for a supply upgrade.
2. Reduced Charging Output
The charger can be configured to operate below 32A where necessary.
3. DNO Main Fuse Upgrade
In some cases, the Distribution Network Operator (DNO) may agree to upgrade the main fuse — for example from 60A to 80A or 100A — if the supply infrastructure allows.
This is not guaranteed and must be approved by the DNO.
Can I Upgrade the Main Fuse Myself?
No. The main fuse is owned and controlled by the DNO.
Only the network operator is permitted to alter or replace it.
Does a Small Main Fuse Prevent Installation?
Not necessarily.
Many properties with 60A supplies can still have EV chargers installed safely using load management.
Need a Supply Assessment?
Before installing an EV charger, your electrical system must be assessed properly.
We provide professional EV Charger Installation in Altrincham, including supply capacity checks, load calculations and DNO notification where required.