Increase hot water cylinder insulation

Priority for Completion: Very High

This recommendation is made when a hot water tank is present in the property and it is not insulated to meet current minimum standards. This means that energy used to heat water is wasted as the hot water stands in the tank. In technical terms, this is known as the standing loss of the tank.

You use hot water all year round so insulating your tank will will save you money even in summer. It can even help keep your home cooler during hot weather. If you use electricity to heat your water the savings are even greater. It is easy to do, even for people with limited DIY skills. Installation will not take long and the materials are relatively cheap. As a result, it usually pays back quickly.

My cylinder is already insulated. Is that enough?

Modern tanks generally have insulation already installed at the factory. If you have a brand new cylinder this is usually enough. However, many older tanks can still benefit from an additional jacket.

The insulation requirements have increased substantially over recent years. The current standard is a minimum of 50mm of factory foam or 80mm of loose jacket insulation. Adding an additional layer of insulation could save a significant amount of money if your tank is not up to these standards.

How much can I save with a hot water cylinder jacket?

Going from a completely uninsulated tank to a well insulated one (by simply adding a jacket) can save you around £150 a year or more, so it is an absolute must if you can see your face reflecting off the shinny cooper hot water tank!

Many hot water tank jackets are available for under £15. At this price, the payback is just a couple of months.

For most of us however, our tanks do have some form of insulation, so the savings won’t be as staggering – but that doesn’t mean it’s not worthwhile! Let’s take a few examples:

Current InsulationTop up Savings per yearPayback
(Assuming cost of £5)
None£100-150under 2 months
25mm Loose Jacket£258 months
38mm Loose Jacket£1810 months
50mm Loose Jacket£101.5 years
25mm Spray Foam£151 year
38mm Spray Foam£823 months
Savings information provided by

As you can see, there are significant benefits from some extra insulation. Take a look in your airing cupboard now and see how thick your insulation is. Remember, if you can see bare metal exposed, you could be wasting a lot of money!

Shouldn't I get a combi boiler instead?

A combi boiler produces both heating and hot water on demand. In many cases they are more convenient than regular boilers since you can do away with the hot water tank. They can also be more efficient as you don't heat water when you don't need it. However, one issue with combi boilers is that, if the water pressure is low in your property then your shower or taps might just trickle.

A modern Regular or System boiler with a well insulated hot water tank can be just as efficient as a combi boiler. This is particularly true if you use a lot of hot water in your home and it is used at consistent times. It is also important to make sure your hot water tank is an appropriate size.

In summary, you may wish to consider changing your boiler but you should seek expert advice first. It is also certainly worth considering insulating your hot water tank whilst you arrange any system change.

Should I also insulate my pipes?

Yes. The hot water pipes that run between your cylinder and your boiler can give off a lot of heat if they are not insulated. In most cases it is really easy to buy some pipe insulation from the DIY store and slip it around the exposed pipes.

Insulating cold water pipes can also be beneficial. This can help reduce the risk of harmful legionella bacteria building up in water standing in these pipes. It also stops these pipes taking heat out of your home and prevent condensation forming on them.

In both cases, insulating water pipes well can also help prevent them freezing in winter. Water expands when it freezes so can cause expensive damage. This is perhaps one of the biggest benefits of good insulation.

Again, you should also check that there are not gaps in your insulation where bare pipes are visible. Birds and small animals also love to use pipe insulation for nesting material. If you have any exposed insulation check to make sure it is not damaged.

Remember to check your programmer

Even the most insulated tank will be wasting you money if you are heating water when you don’t need it. Take a look at your programmer and make sure that it is coming on at the right time and for the right duration. Try reducing the amount of time you heat the water for and see if you notice any difference. If you have a cylinder thermostat, make sure you set it to the right temperature (usually between 65-70 °C). These sorts of things can save you even more money that would otherwise go to heating water you will never use.