When should I use my electric immersion heater?

If you have a fairly old boiler in your home, you may have a hot water tank too. The hot water tank stores the hot water as the boiler produces it, which you can then use as and when you need it.

On the face of it, storing large volumes of hot water is not particularly efficient, since if you don’t use it, it will quite quickly get cold. It is the same principle as boiling a kettle. The more water in the kettle, the more expensive it will be to boil it. There is no point boiling an entire kettle of hot water for one cup of tea, since the rest of the water will quickly cool down and therefore it will waste money.

The major advantage of this type of boiler (and hot water tank setup) over newer combi boilers (which produce hot water on demand), is that you can still get hot water even if the boiler breaks down.

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If a combi boiler breaks down you will have no hot water – that is the bottom line! If you have a hot water tank, provided it has an immersion heater, you can still produce hot water even if the boiler breaks.

Immersion heaters mean you can still get hot water

On top of the hot water tank is an immersion heater. This is nothing to do with the boiler; instead it runs on electricity directly and essentially acts as a huge kettle. This means that even if the boiler is on the blink, you can turn on the immersion heater at the switch and still warm up enough water for a shower or bath.

Heating water with immersion heaters is expensive!

The problem is that heating water with electricity is about four times the price of heating it with gas; therefore it is not advisable unless absolutely necessary!

The number of homes we go into that have the immersion heater on 24/7 would surprise you. This is essentially like boiling an enormous kettle constantly – and it is normally the result of the kids in the family finding a button that a parent in a moment of weakness admits guarantees hot water whenever they need it!

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Often, the two most costly electric items in the home are electric showers (which a few of you might find surprising) and the immersion heater.

If you can keep the immersion heater turned off unless absolutely needed then you are going to save yourself plenty of money.

How do I know if my electric immersion is on?

The first thing to do is follow the wire (where possible) from the immersion heater element at the top of the hot water tank to the wall, where hopefully you will see a switch. If it is on, flick it off!

If you can’t see any wires, then the process is a bit trickier. Since immersion heaters use a lot of electricity though, they normally get fed from a supply directly from your fuse box. You should be able to see a circuit breaker of fuse labelled ‘immersion’ – if this is on the on position, flicking this will stop power going to the unit.

Immersion elements are great for emergencies, but expensive for every day use

Obviously immersion heaters are great as backup – but we really suggest trying to heat water with the boiler where possible. If your boiler is on the blink, you may be happy that you are creating hot water as you need it with the immersion heater. You need to remember that the increased cost you will pay for the electricity would probably cover the cost of calling out a plumber to repair the boiler!


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