Electric water heater not working: causes and what to do

An electric water heater that gives out means a cold shower — literally. The good news is that in most cases the appliance isn't dead: it's one specific part that has failed, and it can be replaced. Before calling anyone, a few simple checks often reveal where the fault is. We'll explain everything, honestly — including what you can sort out without us. For our general method, see our electrical troubleshooting page too.

How an electric water heater works (in 30 seconds)

To understand the fault, you need to understand the beast. An electric water heater — also called a tank or cylinder — is an insulated tank full of water, heated by an electric heating element. A thermostat cuts the power when the water reaches the right temperature and switches it back on when it cools. A magnesium anode protects the tank from corrosion, and a pressure relief valve releases overpressure (that's the part that drips a little during heating — perfectly normal).

Four parts, then, and the fault almost always comes from one of them — or from the electrical supply upstream.

The most common causes of a breakdown

The breaker tripped. The silliest and most common cause. The water heater circuit has its own breaker in the panel; if it has tripped, no heating. Sometimes it's a one-off, sometimes it's the symptom of a real downstream problem (an element shorting to earth).

The day/night contactor is to blame. If you're on an off-peak tariff, a contactor triggers heating at night. If it sticks, your water never heats. Most have a "forced run" position made precisely for testing.

The heating element has burnt out. Over time, and especially with limescale, the element tires and then breaks. The result: no heating at all, or a breaker that trips the moment you switch it back on.

The thermostat is dead. Electronic (with a temperature probe) or mechanical depending on the model, it can stick in the off position (no heating) or, more rarely, never cut off (overheating). Many thermostats have a thermal cut-out with a small reset button.

Limescale has clogged everything. Paris water is hard. A tank that's never serviced ends up accumulating kilos of scale coating the element: it heats less and less, takes hours, then dies. It's the silent cause behind many element failures — the build-up is invisible until the day it gives out.

A leak on the tank. More troublesome: if the tank itself is pierced (corrosion), there's a real leak and replacement is usually unavoidable. Not to be confused with the relief valve dripping, which is normal.

What you can check yourself

You don't need to be a technician for these checks, and they may save you a call-out:

1. Check the breaker dedicated to the water heater in your panel. If it's down, flip it back up. If it trips again immediately, don't force it: there's a fault, and that's where we step in.
2. Check the day/night contactor. On the panel, switch it to forced run (often the "I" or "on" position). Wait an hour or two: if the water heats, your problem is with the off-peak tariff or the contactor, not the heater itself.
3. Look for the reset button of the thermal cut-out. Under the heater's cover (which unclips without tools on many models), a small red button may have tripped after overheating. One press can restart everything.
4. Check for a leak at the foot of the appliance. A puddle, corrosion marks, abnormal water pressure: all worth flagging to us.

If after all that you still have no hot water, the issue is internal — element, thermostat or supply — and it's time to measure.

💡 In doubt, send a photo. Send us a photo of your panel and the heater's label: we can often tell you over the phone whether it's repairable, before even coming out.

What needs an electrician

From here on, we're past DIY: testing an element or a thermostat is done with a multimeter, with the power off, dismantling carefully. That's our job.

In practice, when we step in for a water heater that's stopped working, we measure the element and the thermostat to identify the faulty part, check that the circuit and supply are sound, and replace what needs replacing — element, thermostat, contactor, sometimes the relief valve. If the appliance is heavily scaled, descaling the tank and element often brings back years of service. And if the panel feeding it is dated, we'll tell you what bringing it up to code would involve, without forcing anything on you.

The goal is never to replace for the sake of it. An element and a thermostat are parts costing a few dozen euros: a repair is almost always smarter than swapping the whole appliance.

Repair or replace: we'll tell you straight

There are still cases where replacement is the right call, and we'll say so without beating around the bush: a pierced tank that leaks, an appliance over fifteen years old and fully scaled, or a model whose parts are no longer available. Repairing a heater at the end of its life means buying six months for the price of half a repair — not a good deal.

In every other case — the vast majority — a precise diagnosis and a single part swap will do. The lifespan of a water heater that gets regular servicing (a descale and an anode check every few years) easily passes the decade.

Electrician or heating engineer: who to call?

A quick note that saves pointless calls: we work on electric water heaters (the resistance-heated tanks). If your hot water comes from a gas water heater or a boiler, then you need a heating engineer or a plumber, not an electrician — we don't touch gas, it's a different qualification. If you're unsure about your appliance, call us anyway: we'll point you to the right professional rather than waste your time. On the other hand, if it's a radiator or another piece of electric heating that's stopped responding, that's squarely our domain.

We'll come and run the diagnosis

For a water heater that's stopped heating in Paris or the inner suburbs, we come out to run a proper on-site diagnosis: identify the fault, quote the repair before doing it, and carry it out straight away if you agree. No replacement sold under pressure, no part swapped "just in case".

A glance at our pricing gives you the ballpark for a call-out, and for an intervention or simple advice, contact us by phone or through the form — we usually reply within 48 working hours with a slot and a clear quote before any repair.