The Cost Of Installing Immersion Heaters

All you need to know about the installation of immersion heaters, including costs of installation, materials, labour and time frames.

The Cost Of Installing Immersion Heaters

What the job entails

Although most homes in the UK have a central heating system, there are some homes which use an immersion heater as a backup hot water source. An electric immersion heater is just like a big kettle, heating the water in the storage cylinder using an element and providing hot water on demand even when the central heating is switched off. Immersion heaters can also be set to come on automatically during the off-peak hours to take advantage of lower electricity prices. Unlike a kettle, most hot water cylinders have two or even three heating elements inside. these heating elements will usually last many decades, but nothing lasts forever and eventually you will need a replacement element. This element is usually referred to as the heater and it is usually just the element that is replaced rather than the entire water tank.

In most cases, replacing the heating element is a straightforward job if you are comfortable with basic electrical wiring and simple hand tools. If you are considering replacing an immersion heater element as a DIY project, then first, check the problem is not in the fuse board/consumer unit. Once you have checked this, isolate the circuit in the consumer unit and turn the immersion heater switch off to make sure the immersion heater is electrically safe before proceeding. Next test the heating element and make sure there is no power using an electrical test meter. Then disconnect the electrical wiring and check the thermostat first by setting it to maximum and measuring the resistance across the terminals. If there is continuity then the thermostat is ok, if not, you need a new thermostat. If the thermostat is ok then you need to test the element for continuity, if the meter shows a very high resistance, then the element is open circuit and the heater is broken, so you will need to order a replacement. Before removing the immersion heater remember to drain the tank first.

Purchasing the correct replacement immersion heater is not always as easy as you may think. Often any part or serial numbers are illegible, and you have to resort to ordering an element which looks to be around the right size. This is where using a professional can really pay off, as they will know exactly which part to order without any trial and error.

When you wire in the new immersion heater make sure all the electrical connections are tight before restoring the power, refilling the tank with water and switching it on. You will soon know if the new heating element is functioning correctly or not. If you do not have the time or patience to carry out this job yourself, you can always call in an electrically qualified plumber to change the immersion heater with no problems.

It's easy to tell when your immersion heater goes as often the whole house will be plunged into darkness as the circuit cuts out. What usually happens is that the protective covering on the element breaks down and allows water in. But water and electricity do not mix well, and a short circuit follows which will throw the circuit breaker in the consumer unit. But sometimes it is not so disastrous, and your water will just take forever to heat as the element has scaled up. Note that the electrical regulations must be followed and if you are not a competent person under the regulations do not attempt any electrical work.

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The Cost Of Installing Immersion Heaters

You can actually buy good quality replacement immersion heaters from £20-£40 (individually) depending on the size and whether or not you need a Titanium element for hard water. But the actual price of the part is just a small part of the overall job. You can expect to pay much more to include parts and labour. Plus, you may need to replace two or three elements at the same time in some hot water cylinders as the chances are if one has failed then the others will soon fail if they were installed at the same time.

For a tradesperson to complete this work, this should only take an hour or two typically, unless there are any complications which requires additional time or materials. As a standard rate, this could be expected to be less than £100, but may vary depending on the tradesperson and the region.

Below are some estimated costs of installing immersion heaters.

Job Description Avg. Cost Duration
Changing A Single Element Immersion Heater £120 1-2 Hours
Changing A Double Element Immersion Heater £145 1-2 Hours
Changing A Triple Element Immersion Heater £170 1-2 Hours

Cost Breakdown

Individual costs of changing a single element immersion heater - Total Cost: £120






Waste Removal


Basically, there is a jacketed heating element that inserts into the water cylinder, usually controlled via an adjustable thermostat, but sometimes just an on/off switch or a timer. The element heats water just like the element in a kettle.
Most plumbers will charge for half a day, even though the job will likely take less time than that. The actual time taken will depend on the accessibility of the hot water tank and the immersion heater, along with the number of elements. Ordinarily, a couple of hours should do it, but if you decide to do the job yourself, it could take a lot longer depending on your skill and experience level.
Yes, but ensure that the power supply is isolated before removing the cover or disconnecting the electrical connections from the thermostat. Once power is isolated, you can remove the thermostat and replace with a new one without removing or draining the water tank.
Unvented water cylinders work directly from the mains water supply; whereas vented cylinders are connected via a vent pipe to the cold-water storage tank usually in the loft space.
The main reasons for the immersion heater not working are no electricity supply to the element, over temperature trip in your Immersion heater thermostat has cut out, faulty thermostat, or immersion heater has failed to earth or gone open circuit.
Elements should have a stamp showing the watts, volts, and possibly manufacturer identification. However, if you cannot read this then you need to order a heater of similar size and should get professional advice.