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Hot water tank insulation and jackets

Friday, October 9, 2015

“If you are cold, put a jacket on!” That was often the advice of my mother when I was feeling a little cold.  This is also the best advice for your hot water tank!

Unlike our heating systems, we use and need hot water all year round.  If you have a “combi-boiler”, and have no hot water tank, you can stop reading now.  For everyone else that has a dual hot water/heating system read on and find out how insulating your hot water tank can be one of the easiest, and most cost effective methods of saving money and energy.

Your hot water tanks stores heated water for you to use throughout the day when you need it.  But, the hot water that you have heated may sit there for a few hours before you need it and may cool down, therefore wasting the energy required to heat it, and costing you money.


How much could I save?

The savings that you could make depends on if your hot water tank is currently insulated, and if so, how much insulation is currently on it. Use the table below to see how much you could save.  The savings are based on installing a 80mm (just over 3 inches) thick loose hot water tank jacket, that typically costs about £15 from a DIY store (e.g. B&Q or Wickes).

Current insulation

Approximate savings (per year) Payback time

None (uninsulated)

 "£100 – £150" 2 months

25mm (1") loose jacket

 "£25" 6 months – 1 year

38mm (1.5") loose jacket

 "£18" 1 year – 18 months

50mm (2") loose jacket

 "£10" 18 months – 2 years

25mm (1") foam spray

 "£15" 1 year

35mm (1.5") foam spray

 "£8" 2 – 3 years

If you already have some insulation on your hot water tank great it is not wasted.  You cab simply install another jacket on top of the existing one and increase the thickness up to 80mm.

Installing a hot water jacket is not a complex DIY task and is in fact very simple.  Jackets usually come in one of two sizes: 1050 mm x 450 mm (42″ x 18″) and 900 mm x 450 mm (35″ x 18″).  Make sure to measure your tank before you head off to the shops. Simply follow the manufacturers instructions and make sure that it is tied tightly and is a snug fit.

Don’t forget your pipes!

The hot water pipes going into and out of your hot water tank are also important to remember.  Adding insulation, also called pipe lagging, is another simple way of making sure you keeping your water as hot as possible and not wasting energy and money.  Adding insulation to your pipes is another really simple task.  DIY stores sell pipe insulation in a range of lengths, typically about £5 for 2m (6.5 ft) which simply need pushing around your hot water pipes. Typically you can expect to save about £15 a year and it should cost about £10 to install depending on the size of you hot water tank and length of exposed hot water pipes.

Next steps…

This post has been an in-depth look into hot water tank insulation.  There are still a lot more simple ways to save money and energy around your home. Don’t forget to check out our other in-depth guides in the Know-How section.

Remember that in the meantime you can ask us any questions on Twitter and Facebook.  Follow us for all the latest site updates, and don’t forget to share this story with your friends so we can help even more people save energy and money.


  • Andrew Timmis
  • Posted by
    Andrew Timmis
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