This year, the papers are predicting a bleak winter in what has been termed the “big freeze.” Waking up on a freezing morning and preparing for work or school would be virtually impossible without the prospect of a hot shower.


How do immersion heaters work?

A gas heated water tank is fitted with a burner underneath that helps it to heat water. Conversely, an immersion heater heats water directly inside it. Here, there is a heating element immersed in the water, and a strong electric current is passed through it which causes it to heat the water in contact with it. Compare it to your regular kitchen kettle if you will, just on a larger and slightly more advanced scale. There is a thermostat fitted in the tank that helps to keep the water at a preset temperature.

Basically, you get heated water out of the tank when the influx of cold water supplied from underneath the bottom of the reservoir pushes the hot water out from the top of the tank with enough pressure to move it out of the cylinder. Hot water will naturally rise to the top when heated, In this case, by the immersion element.

The immersion heater wiring will often include an isolating switch where it is connected to the mains electrical supply. While a natural gas heater may be less expensive, an immersion heater does not require as much ventilation. However, it will save cost if a timer is attached to the tank. This ensures that water can be heated up and kept warm in the insulated tank for use when needed.

Who needs an immersion heater?

A central combined heating/hot water boiler is popular amongst many households for the provision of heating and hot water. Although an immersion heater may also be present in some homes as a backup.

However, it is not uncommon to find several flats without gas supply relying primarily on the immersion heater as the only source of hot water.


  • The thermostatic control on an immersion heater will ensure that the temperature of the water is kept constant, by automatically switching on and off the heater as required.
  • Unlike a central heating system, immersion heaters are not connected to a boiler, so even if you have a faulty boiler you can still have a hot shower.
  • A well-insulated immersion heater can keep water warm even after several hours of it being turned off.
  • You can set the immersion heater to heat water at convenient off-peak hours when energy charges are lesser.
  • Immersion heaters are extremely easy to operate and use. They commonly only require you to turn off and on a switch, and regulate the thermostat.


  • Immersion heaters use electricity, and electric heating is generally more expensive than gas heating.
  • A standard immersion heater will cost an average household 50p hourly since on average, it will consume around three kilowatts of energy per hour.
  • Immersion heaters take a while to heat water. This process will cost an average household not less than £360 annually.
  • Despite the unpopular advice of some heating engineers, leaving your immersion heater always on can be quite expensive, unless you have a functional thermostat.
  • The immersion heater would have to heat the water to at least 50°C to effectively kill off any bacteria present in the water.

Skill Training Group offers comprehensive and detailed training on how to fix, maintain and install immersion heaters as a part of one of our plumbing courses.

Find out more by calling FREE now on 0808 164 2780 or filling in the form on the right.

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