Storage Combi Boilers & Which Are The Best Storage Combis?

James Elston
Written by James Elston
Updated on 30th January 2024
Posted on 18th September 2023
Storage Combi Boilers – How They Work & Which Are The Best Storage Combis

What are storage combi boilers?

storage combi

Storage combi boilers are a combi boiler that comes with a hot water cylinder within the boiler unit called a cylinder loading system or CLS.

This water storage within the storage combi boiler allows for water to be constantly heated whilst in the cylinder, meaning hot water can be delivered to all parts of the house when needed such as showers, taps and radiators.

The design of a storage combi boiler combines features from a combi boiler and a system boiler, meaning that there are advantages and disadvantages brought along with it.

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How storage combi boilers work

These kinds of boilers are similar to system boilers in the sense that they have a water storage tank.

Storage combi boilers draw water from the mains water supply and heat it up, offering instant hot water whilst also storing some water in the hot water cylinder, making it able to supply water instantly to different parts of a household without the flow rate of the water being affected.

Ideal Logic C30 combi boiler

Differences from a combi boiler

Like a combi boiler, a storage combi boiler gets water from the mains water supply, offering instant hot water when it’s needed, however, a combi boiler doesn’t utilise a hot water storage tank like the storage combi boiler and a system boiler does.

Having the ability to do this arguably makes these boiler replacements more useful than a standard combi boiler unit, especially when having a high hot water demand.

Differences from a system boiler

Worcester Bosch 4000 gas system boiler

Similarly to a system boiler, storage combi boilers have a hot water tank that store hot water so it is ready for use when it’s needed.

The differences between the two are that the storage combi boiler draws water from the mains water supply as well, so hot water is almost always available on demand rather than having to wait if the hot water cylinder runs out of water.

In addition to that, it is an integrated hot water tank rather than an external one much like a system boiler does meaning less room has to be allocated to install storage combi boilers.

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Advantages of a storage combi boiler

Instant hot water

hot water

A storage combi boiler is able to give instant hot water when it is needed, as it draws water from the mains water supply and heats up the water immediately.

This means that you won’t be getting cold water when the storage tank runs out of hot water and can continue to use it when you’re getting a shower or using the hot water tap.

Read more about how a combi boiler works here.

Can meet high demand for hot water

Most households nowadays will have multiple outlets for heating and hot water to be used, some of them may even need to be used at the same time depending on the size of the house and the occupants. Storage combi boilers can easily meet high hot water demands with its multiple methods of heating and storing water.

There is instant hot water heated from the main supply, but also an internal storage cylinder that will store hot water and keep it heated for when it’s needed. This means multiple outlets can be used for water without the flow rate of it being altered.

They are solar thermal friendly

These kinds of boilers are also ideal for households that use solar energy as the main power source, which is better for energy efficiency. Solar panels are used to keep the separate hot water cylinder heated, meaning there isn’t any requirement to use electricity or gas to keep it hot.

The use of solar thermal energy can also reduce the price of your energy bills, making both solar energy and storage combi boilers an excellent long-term investment.

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small home

Ideal for limited space

Having the internal cylinder for water, a storage combi boiler requires much less room than a system boiler would, as its external tank will require room for it to be installed.

This means more room can be afforded to other things whilst being able to achieve the same things as both a combi boiler and a system boiler.

Cheaper than system boilers

Storage combi boilers are not only able to achieve the same thing that system boilers can and more, whilst requiring less space, but are also cheaper on top of that. Due to the system type of boiler having a separate hot water cylinder rather than having an internal cylinder already built in, it will be more expensive to buy and install with the space and all the different parts needed.

installation complete

Easy to install

Due to the efficient design of a storage combi boiler, they are quite easy for any local boiler installers to put in, as there isn’t any need to install a separate cylinder for water storage. This would require time and space to install, like that of a system-type boiler, but with a storage combi boiler, this hassle isn’t considered.

Disadvantages of a storage combi boiler

More expensive than a combi boiler

Although storage combi boilers are cheaper than system-type boilers and can be seen as more effective, they are more expensive than a conventional combi boiler. Despite the advantages that they have over a normal combi boiler system that may make the price seem worth it, it may not be ideal for households with lower budgets.

A combi boiler may not do all of the things a storage combi boiler does, but many combi boilers are capable of doing what is required of it and may better suit certain homes.

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They are larger than conventional combi boilers

boiler size

Again, despite its advantages in size over system boilers, the storage combi boiler is bigger than a typical combi boiler. That means the space that is allocated for the boiler must be taken into account when thinking of installing one.

For smaller homes or flats, it is very difficult to find the space to install a storage combi boiler and maybe a lot more suitable to go for something smaller, such as a standard combi boiler.

Cylinder size can determine the supply of hot water

Depending on the size of the hot water cylinder within a storage combi boiler, the ability to supply hot water can differ. Bigger storage will obviously be able to meet a high demand for hot water, but smaller cylinders may not be able to achieve as much.

The size of the storage tank can also determine the price for different storage combi boilers, as the higher the hot water demands, the more expensive the new boiler will be. Again, this could be an issue for households with lower budgets that cannot afford to spend as much on a new storage combi boiler.

Read our online boiler size calculator guide here for choosing the right boiler for your home.

What are the best storage combi boiler brands?

There aren’t too many manufacturers that develop a wide range of storage combi boilers for people to choose from.

Despite them being very advantageous in many ways, only a few brands actually produce them, however, we’ll guide you through the best storage combi boilers in our opinion and help you decide which one is the best for you.

Viessmann Vitodens 111-W

Viessmann Vitodens 111-W

We think the best storage combi boiler available for people to buy is the Viessmann Vitodens 111-W. With its cylinder loading system that can store up to 46 litres of water, the Vitodens 111-W can meet the high demand for hot easily and do so quickly and efficiently.

It is available in outputs ranging from 4.7 kW to 35 kW, as well as a high energy efficiency class, this boiler can supply instant hot water easily to multiple different parts of the house and can even fill a bath in under 10 minutes!

Not only is it extremely efficient, with a rating of 98%, but the Viessmann Vitodens 111-W also uses great technology, coming with an LCD touch screen and even optional wireless control for easy use around the house.

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Viessmann Vitodens 222-F

Similarly to the 111-W, the Vitodens 222-F is another great storage combi boiler produced by Viessmann. This boiler comes with a stainless steel heat exchanger to heat up the water with maximum efficiency and reliability.

Viessmann Vitodens 222-F

The Viessmann Vitodens 222-F ranges from outputs of 19 kW to 35 kW at a range of different prices and also a MatriX-Plus burner that minimises emissions, making it more friendly for the environment and your finances.

Another great feature of the Vitodens 222-F is it’s quiet operation which makes it ideal to put in many different places within the household. Kitchens especially are a good place for the Viessmann Vitodens as the quietness of it won’t disturb anyone.

Although this is a storage combi boiler, meaning it doesn’t need as much space as other types of boilers, the 222-F is slightly bigger than the Vitodens 111-W. This probably means that it is more suitable for somewhat bigger homes compared to other storage combi boilers.

Vaillant ecoTEC Plus Combi Store


An alternative to either of the Vitodens boilers is the Vaillant ecoTEC Plus, which can supply hot water in just a few seconds and provide it to multiple outlets around the household.

Of the storage combi boilers that are listed, the Vaillant ecoTEC Plus is the smallest of them, making it ideal for people who don’t have much space to offer for storage combi boiler installation. It has also been given the Quiet Mark, making it another boiler ideal for any place around your home, especially those where people will be present.

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What is a Cylinder Loading System (CLS)?

Cylinder loading systems are cylinders that you find in storage combi boilers to heat up and store the water that is being kept in case more water needs to be used. This is a term used for the cylinder built into the boiler, which is great for saving space.

Cold water at the bottom of the cylinder is pumped through the plate heat exchanger to heat up the water, where it arrives at the top of the cylinder.

How much do storage combi boilers cost?

Prices of a storage combi boiler will differ depending on factors such as the brand, type and output of the new boiler. Here are the typical prices of the boilers we have listed and you will see the new boiler cost is generally higher for these specialist units.

  • Viessmann Vitodens 111-W: £1500-£2000
  • Viessmann Vitodens 222-F: £1700-£3100
  • Vaillant ecoTEC Plus: £1600-£1700

We hope that these prices, along with the advantages and disadvantages shown for each of these new boilers, will help you decide whether a storage combi boiler is for you and, if so, which brand is most suitable.

When thinking about your storage combi boiler cost, you should also take into account the running cost that will come along with it.

Running costs of a storage combi boiler are more expensive than that of a standard combi boiler, mainly due to the fact that it can utilise multiple methods of getting heating and hot water.

The price will be higher as you will have to fund the boiler instantly heating the hot water as well as continuously keeping it heated whilst in the hot water cylinder.

Why you should get a storage combi boiler

Storage combi boilers can offer so much that a system or combi boiler can’t as it takes the benefits of having both and combines them into one.

Although suitable for smaller properties, combi storage boilers are capable of providing for bigger homes as well, with some manufacturers and brands even being more suited to them.

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Written by
James Elston
James Elston Director Of Boiler Central
Posted on: 18th September 2023

James Elston is our resident boiler replacement and heating expert here at Boiler Central. With over 20 years experience in the boiler installation industry, James ensures that he knows everything there is about our Gas Safe boiler installations, energy saving and home heating solutions. This can be from simply procuring the latest best combi boilers, to reviewing and ensuring that Boiler Central maintains the highest standards across our boiler installation company.

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