7kW single-phase AC charging

What a nominal 7kW home chargepoint can deliver, and the supply, vehicle and control checks behind that figure.

A “7kW” home chargepoint is normally a single-phase Mode 3 AC unit designed to make up to 32A available at the UK’s nominal 230V supply. Multiplying those figures gives 7.36kW, which is why otherwise similar products may be described as 7kW, 7.2kW or 7.4kW.

That is the chargepoint’s available AC power, not a promise of what the battery will receive. The vehicle’s onboard charger converts AC to DC and may accept less. Supply limits, dynamic load control and conversion losses can reduce the result further.

Check the vehicle first

The maximum AC rate is set by the lowest limit in the chain:

the property supply and chargepoint circuit
the chargepoint’s configured current
the tethered or detachable cable
the vehicle’s onboard AC charger
any thermal, schedule or site-load limit

A vehicle whose onboard charger accepts less than 7kW will charge at that lower rate. A vehicle capable of three-phase AC charging will still receive only single-phase power from a single-phase unit. A higher public DC figure is irrelevant because DC rapid charging bypasses the onboard AC charger.

Check the vehicle specification for AC charging, number of phases and any model-dependent option. Do not infer AC capability from the size of the traction battery or its CCS rapid-charging figure.

Estimating time without a misleading range figure

Start with the energy the battery needs, not its total advertised capacity. Divide that energy by the average power reaching the battery:

charging time in hours = energy required in kWh ÷ average charging power in kW

For example, adding 21kWh at an average 6.5kW takes about 3.2 hours. The average is below the wall unit’s nominal figure because conversion, battery conditioning and occasional control limits consume or withhold some power.

Miles added per hour is less reliable. Vehicle efficiency changes with speed, weather, heating and route. It is better to estimate the energy needed for the next journeys from the vehicle’s own consumption history.

Supply capacity and maximum demand

Adding a chargepoint creates a long-duration electrical load. The installer must identify the cut-out fuse and service arrangement, assess maximum demand and confirm whether the consumer unit and circuit can accommodate it.

Large loads such as electric heating, an immersion heater, an electric shower or another chargepoint may coincide with charging. If unrestricted charging would exceed the available capacity, the options can include:

a lower fixed charge current
dynamic load management
coordinated control between several flexible loads
work by the DNO

Dynamic control measures site demand and reduces EV current when other loads need the capacity. It can let a nominal 7kW unit run at full output when the home is quiet without assuming that 32A is always spare.

Network notification is not G98

The installer must inform the relevant network operator of an EV chargepoint installation and use the current ENA or DNO process to establish whether notification or prior assessment is required. Looped services, uncertain cut-out ratings and proposed demand beyond the existing connection can require network work or approval before commissioning.

An ordinary one-way AC chargepoint is demand equipment. It is not notified as a generator under G98. G98 or G99 becomes relevant only where bidirectional equipment has embedded-generation capability, with the route determined by that exporting equipment and the rest of the generation at the premises.

The handover pack should include the DNO or ENA submission and any conditions, as well as the commissioned current limit.

Circuit and protection design

The chargepoint circuit must be designed and verified to the current BS 7671 requirements and the equipment instructions. As at 22 July 2026, the current edition is BS 7671:2018+A4:2026.

The design includes conductor rating and voltage drop, isolation, RCD and DC residual-current protection, earthing, open-PEN measures where applicable, equipment location and cable routing. These cannot be reduced to one universal accessory list because chargepoints integrate different protective functions.

The declared output also assumes the circuit can sustain the load in its installed conditions. Cable route, grouping, insulation, ambient temperature and termination quality can all affect the design.

Smart charging and solar

Private chargepoints sold within the scope of the Great Britain smart-charge-point regulations must provide the required smart functions. Compliance does not guarantee compatibility with a particular tariff, vehicle or energy platform.

Solar-surplus charging needs a site meter or CT and control that can reduce or pause the car as surplus changes. A nominal 7kW maximum does not mean the unit can follow any small surplus continuously. The vehicle and control-pilot system have a supported minimum current and may stop when surplus falls below it.

A stationary battery can change the net reading, so priorities must state whether the car may charge from the battery, only from PV surplus or from a mixture with the grid.

When a lower setting is sensible

A 7kW-capable chargepoint does not have to operate at 32A. A lower commissioned limit can be the correct solution where daily energy need is modest, the supply is constrained or a long cable run makes a lower design current appropriate.

Compare the energy that must be added during the real parking window with the reliable available power. A lower rate that finishes before departure is not an inferior system, and it may avoid unnecessary supply work.

Single-phase charging boundaries

vehicle maximum AC power and phase support
chargepoint and cable current rating
actual cut-out and service arrangement
assessed maximum demand and any load-management setting
current BS 7671 design and protective functions
DNO or ENA submission and any connection conditions
usable charging window and energy required, not a generic full-battery time
behaviour during communications or sensor failure