EV Charging

EV Charger Tripping for No Reason? Your Neighbour's Solar Panels Might Be Why

You plug the car in overnight, the charger lights up as normal, and by morning there's barely any extra range. Before anyone assumes the charger is faulty, it's worth knowing that a surprising number of these cases trace back to something several doors down — a neighbour's solar panels.

The grid was never built for two-way power

For decades, the local electricity network only had to move power one way: from the substation into homes. Add solar panels, batteries and EV chargers to the same street and that's no longer true. Power now flows in, out, and sideways depending on sunshine, time of day and who's charging what. On a bright afternoon, houses with solar panels can generate far more electricity than they're using — and most of that spare power gets exported back onto the local network.

Why export pushes the voltage up

To push electricity back through a cable rather than pull it, a solar inverter has to raise its output voltage slightly above the local network voltage. One house doing this barely registers. Ten or twenty houses on the same feeder all exporting at once, on a sunny day, can push the voltage along that stretch of cable noticeably higher — and that affects every property on it, not just the ones with panels.

Why that trips an EV charger specifically

Most UK homes are wired with a PME (Protective Multiple Earthing) supply, where the neutral and earth are combined into one conductor on the network side — the PEN conductor. If that conductor were ever to fail, exposed metalwork on anything connected to the installation's earthing — including a plugged-in car — could become dangerous to touch. EV charging equipment is required under BS 7671 Regulation 722.411.4.1 to guard against exactly that, usually with a device that disconnects the charger if it detects the fault.

The simplest and most common way of building that protection is to monitor voltage: if it rises above roughly 253V or drops below around 207V at the charger, disconnect. It's a sound, low-cost approach — but voltage alone can't always tell a genuine broken PEN conductor apart from a street full of solar panels exporting on a sunny afternoon. To a purely voltage-based protection device, both situations can look identical, so it trips either way.

So is the charger actually faulty?

Often, no. It may simply be doing exactly what it's designed to do, in response to conditions on the wider network rather than anything wrong with the car, the charger or the installation. That's cold comfort when you need the car charged for the morning, but it does mean an installer checking the unit, or even a DNO engineer checking the supply later, can both find nothing wrong — because at that moment, there genuinely wasn't anything wrong.

What can actually be done about it

Newer PEN-fault protection devices monitor both voltage and earth-loop/earth-current behaviour rather than voltage alone, which lets them tell a real broken-PEN fault apart from a voltage rise caused by solar export — and keep charging safely through the latter instead of disconnecting unnecessarily. If a charger is tripping repeatedly with no other explanation, it's worth having a qualified electrician check which type of protection device is fitted, and whether the installation and local supply would benefit from one of the newer dual-sensing devices. In persistent cases it's also worth asking your District Network Operator (DNO) to check voltage levels on your section of the network.