A 7kW home charger is about 32 amps, and it holds that current for hours. An electric shower is a short, heavy load, often around 9 to 10.5 kilowatts. An induction hob is high on the nameplate and lower in real use. Adding those stickers together and comparing them with a 60 or 80 amp cut-out is how rumours start. The survey has to apply diversity properly, or fit load management, or ask the network operator for a larger fuse. It should not be a guess you make from the shower box.
Why the stickers overstate the evening
The shower is on for minutes. The hob cycles. The charger, if you let it, runs steadily through the evening. A competent design uses diversity for loads that do not coincide, and it treats the charger as a long load. That judgement is the electrician's, against BS 7671 and the supply they find, not a total you can trust from a forum.
If the cut-out says 60 amps and the house already has the shower, the honest outcomes are a smaller overnight-only habit, a current clamp that pauses the car when the shower runs, or a service alteration. Pretending the shower is never used at 18:00 is not a design.
What a clamp can and cannot do
A load-management device watches the supply and tells the charger to ease off. The car charges more slowly, or waits, while the shower is on. When the shower stops, the car can pick up again. Guests need to know the car may not be full if everyone cooks and showers at once.
The clamp does not upgrade the network. If the distribution network operator will not accept the connection without a fuse change, a gadget on the meter tails is not a workaround. The installer should say which of those two stories applies to this house.
The cut-out is not the installer's fuse to swap
The service head belongs to the network operator. Asking someone to pull a larger fuse in on a Saturday is how seals get broken and supplies get condemned. A fuse upgrade is an application, with a lead time, and it is a different invoice from the wallbox.
Say whether the quote assumes the existing fuse is enough. Two prices that differ by the cost of a board often differ because one of them has looked at the shower circuit and the other has not.
- Photo of the cut-out rating before the visit
- Shower kilowatts from the unit, not from memory
- Whether a clamp is included, and what it pauses
- Whether a network application is included or excluded
A heat pump makes the same evening busier
If a heat pump is going in the same year, give the charger electrician that load too. Both want long runs of current in cold weather, which is when the shower and the hob are also in use. Sequencing two contractors who each assume spare capacity is how the second one condemns the first one's quote.
None of this changes the charger type for a normal single-phase house. About 7kW is still the sensible ceiling unless the supply and the car are both three-phase.
How to live with a pause
Put the car on to charge when you get home if the supply can take it, and let the clamp do its job during the shower rather than running a 3 pin lead from the landing to avoid the issue. The landing lead is how the shower circuit and the car end up on protection that was never designed for either.
After the install, run the shower while the car is charging once, with the installer still there. You should see the charger back off and then recover. If nobody is willing to demonstrate that, the clamp is a box in a photograph.
Frequently asked questions
Can I just charge after 9pm so the shower is finished?
A habit helps, and an off-peak schedule helps, but it is not a substitute for a supply that can survive the evening you forget. The design should stay safe when the shower and the car overlap.
Does a new consumer unit increase the fuse size?
No. A new board is the house installation. The cut-out rating is the network's limit until they agree to change it.
Will load management slow every charge?
It should only ease off when other loads are high. Overnight, with the shower off, a 7kW charger on a suitable supply can still run at its normal rate.
Core buying guides
Start with these high-intent guides, then dig into the rest of the library.
Related guides
Sources and further reading
How this guide was prepared
This guide was written by the Local EV Installers Editorial Team. We compare official guidance, legislation and established consumer information, separate general information from project-specific advice, and show publication dates and sources. We do not accept installer accreditation claims at face value.