Why a Home Charge-Point Survey Fails — and What Each Fix Costs

Sam Whitfield, UK EV writer & Tesla owner · published 2026-08-28 · figures checked 2026-07-13.

A home charger install is quoted from photos and answered in a survey. The gap between those two moments is where most of the unpleasant surprises live — and almost all of them are electrical rather than anything to do with the car. Here are the six that come back most often, what each one actually is, and how to get a straight number for fixing it.

The order things actually happen in

It helps to know the sequence, because five of the six failures below are decided before anyone visits:

1. You pick an installer and send photos of the meter, consumer unit (fuse board), main fuse and the proposed charger position.
2. A desk survey produces a quote. This is the optimistic number.
3. The installer notifies your Distribution Network Operator (DNO) — the company that owns the cables in the street, which is not your energy supplier.
4. A site visit confirms or revises the quote.
5. Install, then certification and notification to building control.

The published UK install band we use in the Home Charger Cost Calculator is roughly £800–£1500. That band assumes none of the six below applies. Each one moves you up it or past it.

1. Earthing arrangement (the PME / PEN problem)

This is the most common technical objection and the least intuitive. Most UK homes use a supply earthing arrangement called PME (TN-C-S). Wiring regulations treat an outdoor EV charge point on a PME earth as a specific risk, because a fault in the street network could put a dangerous voltage on anything metal you are touching — including a car on your driveway.

There are two accepted resolutions: a charger with built-in PEN-fault detection (most current units have this, which is why it is far less often a problem than it was), or an earth rod driven at the property to create a separate earth. If a survey says you need the rod, ask which of the two the quote assumes, because the price difference is real and the choice is the installer's, not yours.

2. The main fuse is too small — or nobody can see it

A 7 kW charger draws around 32 A on its own. Add a shower and an oven and a modest main fuse runs out of headroom. Installers want to see the fuse rating, and the two failure modes are: it is genuinely too low, or it is sealed and unlabelled and cannot be confirmed.

Upgrading it is not the installer's job — the main fuse belongs to the DNO, and it is a separate application with its own timescale. The workaround is usually load-limiting (a current-transformer clamp on the incoming supply that throttles the charger when the house is drawing heavily) which is cheaper and quicker, at the cost of occasionally slower charging. If you are told you need a supply upgrade, always ask whether load-limiting was assessed first.

3. DNO approval — notify or apply

Charge points up to a certain rating are usually installed under notification: fit first, tell the DNO afterwards. Above that, or where the supply is already loaded, it becomes an application: permission first, which takes weeks and can come back requiring reinforcement work.

This is the single biggest cause of a charger not being live for delivery day. If your car has a delivery estimate, start the charger process at the point the order is placed, not at the point the delivery date firms up. There is nothing you can do to accelerate a DNO queue.

4. Consumer unit condition

A charge point circuit needs the right protective device, and it has to go somewhere. An older board with no spare ways, no RCD protection, or a design that cannot accept the required device means either a new consumer unit or a separate small enclosure next to it. Both are legitimate; they are priced very differently.

Get this one itemised. "Board work" as a single line on a quote is the least transparent thing on the page.

5. Cable route and distance

Every metre from the board to the charger is cost, and the expensive part is not the cable — it is what the cable has to cross. Going through a wall is cheap. Going under a driveway is not. A detached garage on the far side of a block-paved drive is the classic case where a £800 desk quote comes back at multiples of that.

Measure the route before you request a quote and say what it crosses. It costs you nothing and it makes the first number honest.

6. The grant rules are the opposite of what people assume

The EV chargepoint grant is worth up to £350 and is claimed by the installer, applied to your invoice — you never handle it. The part that catches people is eligibility: the current scheme is aimed at renters and flat owners, not at owner-occupiers of houses with off-street parking, who were the original target years ago and largely are not eligible now.

Check the live rules at GOV.UK before you build it into a budget, and confirm your chosen installer is authorised to claim it — not all are, and it cannot be claimed retrospectively.

How to get a quote that does not move

• Photograph the meter, the main fuse, the consumer unit with the cover off if it is safe to do so, and the charger position.
• State the cable route length and what it crosses.
• Ask explicitly: does this quote assume an earth rod, a consumer-unit change, or load-limiting?
• Ask whether it is a DNO notification or an application, and what the current lead time is.
• Ask for the grant to be shown as a separate line, so you can see the pre-grant price.

Five questions, asked before the survey, remove most of the variance. Then put the resulting figure into the Home Charger Cost Calculator against your own mileage and tariff — at a home rate of 7.5p/kWh off-peak versus 41p/kWh at a Supercharger, the payback arithmetic is what decides whether a bigger install quote is still worth accepting.

Where the referral fits — and where it does not

It does not fit here at all, and that is worth being clear about. The 650 free Supercharging miles are a Tesla benefit attached at order time; no part of the charger install touches them, and no installer can affect them. They do change the arithmetic in one direction though: 650 miles of free public charging buys you time, so a DNO delay that would otherwise be painful is more survivable than it looks.

A verified code, if you have not ordered yet

This post discloses referral links plainly: they are marked rel="nofollow sponsored", and we (or the pooled owner) may earn Tesla credits if you order through one — it costs you nothing extra. Tesla VoltBench is not affiliated with, endorsed by, or sponsored by Tesla, Inc. Full referral disclosure.

Next: run the numbers on the Home Charger Cost Calculator, or start from the full calculator hub.