EV charger load balancing: protecting your main fuse and sharing power

A 7 kW charger draws 32 amps for hours on end. Add an electric shower, an oven and a heat pump, and the total can approach the rating of your main fuse. Load balancing – sometimes called load management or load limiting – makes the charger give way automatically, so you do not need a bigger supply just to charge a car.

Why it matters in the UK

Most homes have a single-phase supply with a main fuse that is often rated somewhere between 60 and 100 A; the rating is usually printed on the fuse carrier. A 32 A charger is a large share of that. When your installer notifies the network operator (DNO) of a new charger, they assess the location, the supply options and whether load limiting is needed to avoid overloading your connection ¹. For homes with a maximum demand between 60 A and 100 A, network operators aim to confirm whether the connection is suitable within 10 working days ¹.

A charger with working load balancing often means the difference between a simple installation and a wait for the network operator to upgrade your fuse or cable.

How it works

1. Measure. A current clamp on the meter tails (or a compatible meter) reports the total current into the house.
2. Compare. The charger knows the limit – for example your main fuse rating minus a safety margin.
3. Adjust. If the house load rises, the charger lowers its current. If the headroom falls below 6 A (the lowest current the charging standard allows), it pauses until there is room again.

This happens within seconds. Most of the time you will not notice anything except that the car is occasionally full a little later.

Static versus dynamic

• Static: the installer caps the charger at a fixed current, say 20 A. Simple, but you always charge slowly, even at 2 a.m. when the house uses almost nothing.
• Dynamic: the charger measures continuously and uses all the headroom available. This guide is about dynamic load balancing.

What our data shows

60 of the 67 chargers in our database (90%) list load balancing. That sounds settled, but check the details:

• It may only work with a specific clamp or meter from the same manufacturer, sold separately.
• Some manufacturers mean sharing power between chargers, not between charger and house.
• On three-phase supplies, check whether the charger balances each phase separately.

Ask what hardware is needed, whether it is included in the installation quote, and what happens if the clamp loses connection: a good charger falls back to a safe, low current.

Measuring options

The same clamp that measures import also measures export, so dynamic load balancing is half of what you need for charging from solar surplus. See EV chargers that charge on solar surplus.

Two cars, one supply

For two cars you can fit a charger with two outlets (7 models in our data) or two chargers that share power. Either way, the sharing should also consider the house load; otherwise the two cars split a fixed cap even at night, when far more capacity is available.

On a three-phase supply, 1↔3 phase switching helps when one phase is heavily loaded or when you want to charge from solar: see EV chargers with 1↔3 phase switching (10 models in our data).

Load balancing and smart charging rules

Home chargers sold in Great Britain must be able to respond to signals and, by default, avoid charging in weekday peak hours ². That is about the wider grid; load balancing is about your own fuse. They work side by side: the charger first respects your supply limit, then follows the schedule or tariff you choose.

Checklist for your installer

• What is my main fuse rating, and what limit will the load balancing use?
• Which clamp or meter is used, and is it in the quote?
• Is the link between clamp and charger wired or wireless?
• What does the charger do if the measurement fails?
• Who submits the DNO notification, and does it state that load limiting is fitted ³?

Compare models and their load management options on the EV charger overview or side by side in the comparison tool.