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The Immersion: The Most Expensive Switch You Might Be Using Without Realising

The Immersion: The Most Expensive Switch You Might Be Using Without Realising

Why Older Immersion Systems Cost You More

 

 

In many older homes, immersion heaters were installed long before modern heating controls existed.

That means:

 

  • A manual on/off switch

  • No timer

  • No thermostat control

  • Often no label (so it’s anyone’s guess)

 

 

If you don’t know whether it’s on or off, the immersion can quietly heat water all day long, using electricity continuously — even when nobody is home.

 

That’s money literally being burned behind the scenes.

 

 

The “Set It and Forget It” Problem

 

 

Because immersion heaters work silently, people often leave them on “just in case”.

But here’s the truth:

 

An immersion left on unnecessarily can add hundreds of euro a year to your electricity bill.

 

It’s one of the most common causes of unexpectedly high energy costs in older homes.

 

 

Modern Timers Change Everything

 

 

This is where modern controls make a huge difference.

 

By installing a timer, your immersion only heats water when you actually need it:

 

  • Morning showers

  • Evening use

  • Short heating cycles instead of all-day power draw

 

 

You decide:

 

  • When it turns on

  • How long it runs for

 

 

No more guessing. No more forgotten switches.

 

 

Add a Thermostat = Even Bigger Savings

 

 

A thermostat takes things a step further.

 

Instead of heating water endlessly, it:

 

  • Stops heating once the water reaches the set temperature

  • Prevents overheating

  • Reduces wasted electricity

 

 

Connecting the Immersion to Your Heating System

 

 

Even better again — your immersion can be linked to your heating controls.

 

That means:

 

  • Your boiler does most of the work

  • The immersion acts as a backup, not the main source

  • No more accidental all-day electric heating

 

 

It’s a smarter, more efficient way to run your home.

 

 

Why This Upgrade Makes Sense Now

 

 

This isn’t about fancy tech or unnecessary upgrades.

It’s about:

 

  • Control

  • Clarity

  • Saving money every single month

 

 

For many homes, this is one of the simplest and quickest improvements you can make — with savings you’ll feel immediately.

 

 

The Bottom Line

 

 

If your immersion:

 

  • Is controlled by a mystery switch

  • Has no timer

  • Has no thermostat

  • Or hasn’t been touched in years…

 

 

…it’s probably costing you far more than you realise.

 


 

 

A Gentle Word from King Electrical

 

 

At King Electrical, we regularly help homeowners take control of their immersion and heating systems — making them safer, smarter, and far more efficient.

 

If you’d like to:

 

  • Reduce your electricity bills

  • Understand what’s actually controlling your hot water

  • Upgrade an older immersion system properly

 

 

We’re always happy to give honest advice and practical solutions — no pressure, no jargon.

 

Sometimes, saving money really is just about turning the right thing off at the right time. 

Kate Scully

23.01.2026

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