Earthing arrangements and what they mean for EV charging
How your property's earthing arrangement affects EV charger installation, open-PEN protection and earth rods — explained without jargon.
Two identical houses on the same street can get different EV charger quotes, and the usual reason is earthing. Your property either takes its earth from the supply network or from an electrode in the ground, and charge point requirements differ between them.
This is not an upsell — it is the single biggest technical variable in a domestic charger installation, and it is why we survey before quoting.
- TN-C-S (PME): earth supplied by the network, needs open-PEN protection outdoors
- TT: earth from a local electrode, needs a verified rod and appropriate RCD
- Many modern chargers include open-PEN protection built in
- The arrangement is confirmed by inspection, not assumed
Why outdoor equipment is treated differently
With a PME supply there is a rare but real risk that a break in the network's combined neutral-earth conductor makes exposed metalwork live. Indoors this is contained; outdoors, with someone touching a car, it is not. Regulations therefore require either open-PEN protection or a separate earth arrangement for the charging equipment.
What that means in practice
Most current charge points include open-PEN detection, which resolves it without an earth rod. Where a unit does not, an electrode is installed and tested. Either way it is designed in at survey rather than improvised on the day.
TT properties
Properties on a TT arrangement — more common on rural and some older supplies — rely on an electrode. We measure the electrode resistance rather than assuming the existing rod is still doing its job.
Common questions
How do I know which I have?
It's identified at the incoming supply. We confirm it during the survey — photos usually show it.
Does TT earthing cost more to charge on?
No difference in running cost; it can affect installation cost if an electrode is needed.
Can any charger be fitted to any supply?
No — the earthing arrangement partly determines which units are suitable, which is why we survey first.
Get a fixed price
Photo of your incoming supply and consumer unit is usually enough for us to confirm your earthing arrangement and quote accurately.