Help & Support

Energy efficient water heating

Immersion heaters

Immersion heaters are a convenient way to heat water as they allow you to heat as much or as little water as you need. However, you can save up to 30% on running costs by taking a few simple steps.

Typical 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.
  • It takes about 2.5 hours to fully heat 120 litres from cold.
  • Heating a smaller quantity (normally 40 litres) using the "sink" switch will cost about €0.45 and take about 50 minutes to fully heat.

How to reduce immersion heater running costs

STEP 1 - Insulate the cylinder

Immersion heater lagging jacket

  • Insulate the hot water cylinder using a good quality, 80mm (3") thick lagging jacket and follow the manufacturer’s fitting instructions carefully. This will save up to 30% on your water heating costs and will pay for itself in months.
  • Look out for international approval standards on a new lagging jacket before buying.
  • As a general guide, you should also insulate water pipes inside the hot press area.
  • Buy a factory-insulated hot water cylinder if you are replacing your old one. Talk to your plumber about the best options.

STEP 2 - Control the immersion heater

Count down timer

  • Install a count down timer for occasional hot water requirements. These need just a simple push of a button to start heating the water.
  • For regular hot water requirements, use a programmable time switch which will supply hot water when you need it. It will also prevent your immersion from running longer than necessary.
  • Choose one with a ‘timed-boost’ facility to allow a manual top up of hot water, if required.

Programmable timer


You should also consider having the sink / bath switch and time switch located outside the hot press for ease of access. If your immersion element regularly fails because of lime build-up, consider buying a replacement element with an Incoloy Sheath. It will cost you a little more than the standard copper element but it will last longer.

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