Do you need to increase the main fuse for EV charging?
Not always. The answer depends on the building's main fuse, real load profile, phase loading, number of chargers and whether charging can be dynamically controlled.
Short answer
If the building has enough spare capacity during the day, EV charging can often fit within the existing grid connection. Dynamic load management measures building demand and reduces charging current when other loads rise. The need for a main-fuse upgrade should only be confirmed after reviewing load data and the electrical installation.
Main-fuse sizing is not just arithmetic. Cables, protective devices, phase balance, residual-current protection, earthing and installation condition must also be checked. The final electrical solution must be confirmed by a qualified professional.
What does the main-fuse rating actually tell you?
In a three-phase 400 V system, roughly 3×16 A corresponds to about 11 kW and 3×32 A to about 22 kW. This describes a charger's possible nominal power, not how much capacity the building actually has available for charging.
For example, a building with a 3×63 A main fuse does not mean 32 A per phase is always free for a 22 kW charger. Cooking, heat pumps, lifts, ventilation, water heating and other loads may be running at the same time.
When does dynamic load management help?
Load management helps when building demand varies and spare connection capacity exists part of the time. The system measures current demand and allocates chargers only the capacity that is safely available.
- building demand rises → charging power is reduced
- building demand falls → charging power increases
- multiple chargers → spare capacity is shared between them
- phases are monitored separately to avoid overloading one phase
What data is needed before deciding?
For a preliminary assessment, the main-fuse rating, building use, major existing loads and desired number of charge points are often enough. For a final decision, the most valuable input is the real load profile by phase.
- main-fuse rating and connection type
- actual phase loading
- daily and weekly load profile
- number of chargers and desired maximum power
- condition of switchboard, cables and protective devices
Frequently asked questions
Can you charge an EV with a 3×25 A main fuse?
Often yes, but charging power must fit alongside other simultaneous loads. A definite charging rate cannot be promised from the fuse rating alone; building demand and the installation must be assessed.
Does one 22 kW charger require 3×32 A?
A 22 kW three-phase AC charger is roughly 32 A per phase at full output. That does not mean the building's main fuse must simply be increased by that amount; load management can limit charging according to spare capacity.
Is a main-fuse upgrade always more expensive than load management?
Not always. Cost depends on the grid operator, connection, required construction work and number of chargers. The options should be compared using site-specific data.
Need an answer for your site?
HUBCORE can assess the main fuse, load profile, charger count and suitable control approach using your building data.
Request a technical pre-assessment