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A Complete Guide to Storage Combi Boilers

If your household has high hot water demand and you want to make the most of your home with limited space, a storage combi boiler could be a suitable fit for your property. 

Before you jump in and purchase a new boiler, you should do some research to determine whether a storage combi boiler is an appropriate solution for your home. 

This guide explains everything you need to know about storage combi boilers to help you decide on a suitable new boiler for your home and needs. 

What is a storage combi boiler?

A storage combi boiler works similarly to a combi boiler but comes with a cylinder for storing hot water. The hot water cylinder is within the boiler itself, meaning it doesn’t require a separate cylinder. 

This type of boiler combines the benefits of a combi boiler and a system boiler and can deliver hot water to multiple taps, baths and showers at once while maintaining the flow rate. 

How does it differ from a combi boiler and a system boiler?

Like a storage combi boiler, a combi boiler draws water directly from the mains supply and heats water on demand. However, a combi boiler does not have an internal cylinder and cannot store hot water. A combi boiler is often the ideal choice for homes without a high demand for hot water because it struggles to support multiple taps or showers that are in use at once.  

A system boiler requires a separate cylinder for storing hot water, whereas a storage combi boiler stores hot water inside a built-in cylinder. So, because a system boiler needs extra equipment (a separate cylinder), it requires more space than a storage combi boiler.  

How does a storage combi boiler work?

A storage combi boiler gets cold water from the mains and heats and stores it inside its internal cylinder. The hot water is then sent to your radiators or taps and showers when required, meaning you can enjoy hot water on demand. 

Since a storage combi boiler contains a hot water cylinder, it can deliver hot water to several taps or showers at the same time without losing any pressure or affecting the flow rate. 

Advantages of a storage combi boiler

If you’re thinking about purchasing a storage combi boiler for your home, you should consider the advantages of getting one installed.

The advantages of a storage combi boiler include:

Its built-in hot water cylinder

With a storage combi boiler, you don’t need to find space in your home to store a separate hot water cylinder because it has a built-in cylinder. 

Can meet high heating and hot water demands

Combi storage boilers can meet high heating and hot water demands, something most combi boilers cannot do. So, if you tend to use a lot of hot water at home, a storage combi boiler will provide enough hot water for multiple users and deliver a constant supply of hot water to any number of taps at one time.

Costs less than system boilers

If you have a high demand for hot water, a boiler engineer may recommend getting a system boiler for your home. However, a system boiler requires a separate cylinder that will increase the cost of your new boiler and the installation. The alternative is to opt for a storage combi boiler with a built-in cylinder, which is a more affordable option when it comes to costs. 

It is solar thermal compatible

As a combi boiler does not store water, you cannot use solar power to heat water. But when you get a combi storage boiler installed, you can use solar thermal heating panels to keep the water inside the boiler’s internal cylinder warm. The benefits of using a solar thermal compatible combi storage boiler include making your home more energy-efficient, lowering your carbon footprint and reducing your heating bills.

Disadvantages of a storage combi boiler

Storage combi boilers have several advantages over combi boilers and system boilers, but there are a few downsides you need to be aware of as well. 

The disadvantages of a storage combi boiler include:

More expensive than a combi boiler

We mentioned above that a storage combi boiler is cheaper than a system boiler but will likely be more expensive than a standard combi boiler because it contains a storage cylinder. 

It is bigger than a standard combi boiler

A combi storage boiler is larger than a standard combi boiler because it has a storage cylinder, something a combi boiler doesn’t have. Some combi storage boilers are wall-mounted units, and the boiler dimensions will depend on the size of its cylinder. 

The cylinder size determines how much hot water you can access

Not all storage combi boilers are the same because each model varies when it comes to the size of the built-in cylinder. The bigger the cylinder, the more hot water it can store. That means you need to consider how much hot water you will use at once and how long it will take for the cylinder to refill to determine the correct size for your home and needs. 

Which brands manufacture storage combi boilers?

The short answer is – not many. Very few manufacturers offer storage combi boilers as an option, but the brands that do are well-known for making reliable boilers. These brands include Viessmann, Vaillant and Glow-worm. 

Let’s look at all of the storage combi boilers available on the market right now.

Viessmann Vitodens 111-W

The Vitodens 111-W from Viessmann is a wall-mounted combi storage boiler ideal for homes with two bathrooms and high demand for hot water. With superior hot water performance equivalent to a separate 150-litre cylinder, this boiler comes with a 26kW or 35kW output and a 46 litre integrated stainless steel storage cylinder. In addition to having the capacity to fill a standard bath in 8 minutes, the Vitodens 111-W can supply hot water to multiple taps or showers at once.  

Dimensions: 900mm (H) x 600mm (W) x 480mm (D)

Warranty: 5-year guarantee with the option to extend by a further 7 years 

Viessmann Vitodens 222-F

Available with outputs of 19kW, 26kW or 35kW, the Viessmann Vitodens 222-F is a floor standing storage combi boiler that has a built-in hot water storage cylinder with a capacity of 100 litres. It comes complete with an integrated Wi-Fi interface for internet connection and an Inox-Radial stainless steel heat exchanger to provide exceptional reliability and high condensing efficiency. 

19kW and 26kW boiler dimensions: 1425mm (H) x 600mm (W) x 595mm (D)

35kW boiler dimensions: 1625mm (H) x 600mm (W) x 595mm (D)

Warranty: 5 year guarantee

Vaillant ecoTEC Plus Combi Store

The Vaillant ecoTEC Plus 38kW combi storage boiler has a 15-litre actoSTOR cylinder and can produce 20 litres of hot water per minute. Built with premium components and manufactured in the UK, this combi storage boiler from Vaillant can be fitted to a wall if you wish and has been awarded the Quiet Mark accreditation thanks to its quiet operation. 

Dimensions: 720mm (H) x 440mm (W) x 625mm (D)

Warranty: 5-year guarantee, with 7 to 10 years available if installed by a Vaillant Advance installer

Glow-worm Energy 35 Store Combi

Perfect for medium and large-sized homes with multiple bathrooms, the Glow-worm Energy 35 Store Combi has two 21 litre water storage cylinders and provides a short re-heat time of under 5 minutes. It can be mounted on a wall, has a stainless steel heat exchanger to ensure excellent performance and exceptional reliability and is LPG compatible without a conversion kit.

Dimensions: 890mm (H) x 470mm (W) x 561mm (D)

Warranty: 5-year guarantee out of the box with the option to extend

How much does a storage combi boiler cost?

The table below includes each combi storage boiler we mentioned above, their central heating outputs and their typical prices. Please be aware that the prices in the table do not include installation costs. 

Storage Combi BoilerCH OutputTypical Price
Viessmann Vitodens 111-W 26kW£1,518
Viessmann Vitodens 111-W 35kW£1,632
Viessmann Vitodens 222-F19kW£2,474
Viessmann Vitodens 222-F26kW£2,516
Viessmann Vitodens 222-F35kW£2,606
Vaillant ecoTEC Plus Combi Store 38kW£1,695
Glow-worm Energy 35 Store Combi35kW£1,555

If you’re still unsure whether a storage combi boiler is ideal for your needs, you should ask a Gas Safe registered engineer to visit you in your home and make a recommendation. 

Once your engineer has helped you choose a boiler they think best fits your requirements, you can compare installation quotes to find the best deal and save money on a new boiler. We suggest you get quotes from different trusted boiler installers, which you can do for free by completing our online form.