Immersion Heaters – All You Need to Know

All You Need to Know About Immersion Heaters

What is an immersion heater?

Immersion heaters are electric heating elements that are found inside hot- water cylinders and designed to heat water. They act a little like a kettle and heat the surrounding water in the cylinder.

How does an immersion heater work?

Immersion heaters are connected to their own power supply via a cable. A strong electric current is passed through the element which heats the water around it.  Immersion heaters heat water directly from inside the tank and when hot, the water rises to the top.

boiling water

Do immersion heaters use a lot of electricity?

Average running costs for your immersion heater Heating one full cylinder (normally 120 litres) will cost about €1.30 per day. Actual usage costs will vary depending on cylinder size and the demand for hot water.

How long does it take to heat your immersion?

The average gas heater takes between 30 and 40 minutes to fully heat up the water in its tank. The average electric heater takes about twice as long as the average gas heater to fully heat up the water in its tank, so you can expect it to take between an hour and an hour and 20 minutes to heat up.

Is it cheaper to leave your immersion heater on 24/7?

  • Some think that it is more expensive to heat from cold so leave their immersion on all the time believing it is the cheaper option. However, it is almost always cheaper to have your hot water on ONLY WHEN NEEDED, it is not necessary to leave it on all the time as a full tank of hot water will always lose heat and need topping up by the boiler.
  • Turning off your immersion overnight is a better way to save money on heating bills is to set back the temperature of your home at least 8 degrees for 8 hours or longer (while you sleep). In fact, you can save 1% on your heating bill for every degree that you lower the thermostat.
  • The main issue with immersion heaters is that you have to heat a whole tank of water when you may only need a small amount. Heating water using electricity is more expensive than heating water with gas. However, fitting a thermostat and timer alongside the immersion can help to keep energy use under control.
bath with hot water
Benefits of immersion heaters?
  • The main benefit of keeping an immersion heater is as a backup supply of hot water. Immersion heaters have their own electricity supply and do not rely on boilers to work. This means that if your boiler breaks down you will still have access to hot water.
  • Your immersion heater can be turned on and off at the flick of a switch so you can keep its energy use under control when it is not needed.
  • An immersion heater with thermostatic control will automatically turn itself off when the water reaches your desired temperature and turn it back on if the temperature cools too much.
  • If you install an immersion heater timer you can set it to automatically heat up at specific times of the day or night. If your energy tariff is cheaper at night this would be the best time to have it working.

How to improve your immersion’s efficiency?

  • Firstly, make sure you choose the right size immersion heater to suit your family’s needs.  NEVER have an immersion replaced or installed by anyone other than an approved engineer. 
  • Having a thermostat and timer fitted alongside the immersion can help to keep energy use under control.
  • Proper maintenance of your immersion heater will drastically improve performance, efficiency, and increase lifespan.
  • Being proactive about heater care saves money and increases safety.
  • Check for damage to all switches, fittings, insulation and thermostats.
  • Insulate the cylinder and pipes.
  • Install a timer / booster switch.
  • Use the ‘sink/bath’ switch.
  • Buy a pre-insulated cylinder.
Problems with your immersion?

If the water is not heating up efficiently or not heating up at all, then it could be a sign of a faulty thermostat or element. This will need to be tested by a proficient plumber or electrician.

If the water is heating up to an extreme, the thermostat may be stuck on the ‘on’ position and will need replacing.

Another common problem can be the timer switch burning out, which would also require replacement.

Still Need Advice?

Call us today on 01 497 9838. We have over 30 years’ experience in the industry and our team of professional engineers are fully RGII registered. Give us a call for a no obligation chat regarding problems with immersion heaters, gas, and combi boilers, leaking pipes and more!