Storage combi boiler – What are they and how do they work?

storage combi boiler internal

Storage combi boiler with a built-in tank – Are they any good?

A storage combi boiler is simply a combi boiler that has an integrated thermal water store. This is basically a hot water tank housed inside the boiler unit instead of outside, combining the best of both worlds.

A standard combi boiler heats cold water from the mains supply, but a storage combi boiler stores hot water in an internal tank meaning it can deliver lots of hot water to multiple outlets at the same time, something that a normal combi boiler would struggle with.

Let’s find out why this may be the perfect option for your home if you don’t want a system boiler but the combi boiler can’t cope with your hot water demands.

How do storage combi boilers work?

Storage combi boilers produce pressurised hot water and deliver it to your home, just like a system boiler that uses a separate hot water cylinder. The main difference is that the storage combi boiler unit houses the hot water cylinder within.

vaillant storage combi boiler inside

These boilers can store heated water in this manner, allowing them to provide hot water to multiple taps, baths, and showers simultaneously without affecting the flow rate.

The boilers can produce up to 25l/min flow rates, but this depends on the flow rate of your cold water.

Many boiler manufacturers used to offer larger floor-standing storage combi boilers. Because of their size, there was limited space where they could be placed. Many boiler manufacturers now offer compact storage combi boilers, which can be wall-mounted and installed anywhere.

Why choose a storage combi boiler?

There isn’t enough space to install a hot water cylinder

Storage combi boilers can supply hot water equivalent to a 150L unvented boiler and cylinder with an integrated hot water tank.

This is possible without the need to have a separate cylinder like a system boiler. You can still have all the benefits of a system boiler but without the hot water cylinder taking up space in your airing cupboard.

What are the components of a storage combi boiler?

Here are some of the main components that set apart these boilers from a normal combi boiler or system boiler. Storage combi boilers combine the following over a typical combi boiler.

  • Steel loading cylinders that store hot water
  • Built-in powerful heat exchangers for high water flow rate
  • Variable speed combustion fans
  • Integral expansion vessel for controlling the increase in excess pressure
  • High-efficiency pump for delivering lots of hot water at once
vaillant storage combi boiler

A system boiler is not suitable or wanted

This type of boiler can be used as a substitute for a system boiler in households that do not have enough space. With this heating system, the hot water tank is built-in, so even if you do have space, you could remove a hot water cylinder and create space.

The property has multiple bathrooms and showers

A storage combi boiler should be considered if your property has more bathrooms. This is because it can provide multiple outlets at the same time without a drop in pressure, unlike a conventional combi boiler such as the Worcester Bosch 4000 or the Viessmann Vitodens 050-w

Good for the high demand for hot water

A storage combi boiler is ideal for large families or those with growing children. You will find that multiple members of your family will need hot water simultaneously which means you have high hot water demand.

A storage combi boiler can deliver hot water at the right time to all outlets, regardless of whether you are using the hot water tap for the bath, the shower, or the kitchen sink.

They are simple to install

Storage combi boilers can be set up quickly and easily for the engineer. This means that you’ll have hot water and heating sooner. This saves time too as there is no connecting or installation or a hot water storage tank.

What properties is a combi boiler with a storage tank suitable for?

Combi boilers with tanks of smaller sizes are best suited for larger apartments and flats that have limited space but require lots of hot water at once. If you are unsure, get a Gas Safer registered installer to have a quick look for you.

Storage combi boilers with larger water storage capacities are best suited for larger families with multiple bathrooms.

No matter if you live in an apartment, semi-detached, detached, or terraced house, a storage combi boiler will work for you if your household has high hot-water demands. If you can work out how much hot water you need at any one time then it would really help in the decision making.

The advantages of a Storage Combi Boiler

  • Open vent and system boilers are cheaper to buy and install
  • It is great for saving space, no need to install hot water cylinders or attic tanks.
  • It is easy to set up and install.
  • Some models are compact and can be fitted inside a kitchen cupboard
  • There are options available for properties of any size
  • They can simultaneously deliver hot water from multiple sources.
  • These boilers offer the same savings as a standard combi boiler but only provide hot water when it is needed.

Advantages and Disadvantages of a Storage Combi Boiler

  • Storage combi boilers are more expensive than standard ones
  • These combi boilers are larger than the standard ones.
  • There is less choice of boiler system than conventional combi boilers

How big a storage combi boiler do I need?

It is important to take into account the dimensions of your property and how much water you will be heating throughout the boiler before choosing a storage combi boiler. If you have the space, don’t hesitate to use it.

One of the main new storage combi boiler advantages and significant benefit is its space-saving. This is why CLS (Cylinder Loading System) or built-in hot water storage tank has been so popular in the industry.

Storage combi boilers like the Viessmann 242-F and 222-F provide domestic hot water convenience with double the capacity (200 to 300 L).

What is CLS (Cylinder Loading System Technology)?

This term is often used to describe storage combi boilers. But what does it really mean? Unvented cylinders are heated by a heating coil. CLS technology replaces the heating coil with a plate heat exchanging unit. A DHW (Domestic Hot Water Pump) circulates cold water from the bottom to the top of the cylinder through the plate heat exchanger, and then returns the hot water to the top.

Storage combi boiler prices

The storage combi boilers cost can have a major impact on your decision to install a new boiler. Storage combi boiler cost is higher than conventional combi boilers due to the size and technology

A decent storage combi boiler will set you back around £1,400, not including installation. This price will vary depending on the model and technical features of your boiler. Price will also be affected by the size of the storage tank for the boiler.

How much does a storage combi boiler cost including installation?

Storage combi boiler installation costs are around the same as a normal combi boiler plus the cost of your boiler. So if a normal combi boiler installation costs around £1,000 including all the parts and labour then expect to pay over £2,500.

The installation cost is important. It is expensive to install a boiler. An accurate estimate of the cost of installation is important if you want to avoid unexpected expenses that could impact your budget.

What is the running cost of a storage combi boiler?

A storage combi boiler costs slightly more to operate than a combi boiler. This is due to the fact that the boiler must keep the tank’s water hot. Solar thermal can be used to heat the tank water.

A storage combi boiler has a lower energy consumption than a combi boiler, but the long-term costs of operating a storage boiler are much the same. Storage combi boiler installation, servicing, and maintenance are three of the most expensive costs.

The Best Storage Combi Boilers in the UK

1. Viessmann 111-W Storage Combination Boiler

We believe the Viessmann Vitoden 111-w is the best storage combi boiler in terms of cost, space-saving and performance.

viessmann vitodens 111-w storage combi boiler

This high-performance storage boiler is ideal for larger homes or families who require hot water frequently.

This storage combi boiler, which features CLS technology (Cylinder Loading System), produces 18 litres per minute of hot water and a 46 litre stainless steel storage tank. It can also supply a sink and washbasin.

All Viessmann boilers can modulate energy consumption between 5kw to 30kw when they are not in use.

This saves you money on energy bills. Advanced sensor technology ensures that constant output temperatures can be maintained, even when there is high demand.

The storage combi boiler can be controlled by the Viessmann ViCare smartphone app and a thermostat.

Viessmann Vitodens 111-W Storage Combi Boiler Key Features

  • Dimensions (HxWxD): 900mmx600mmx480mm
  • Cylinder loading system with integrated stainless steel storage tank
  • Control via backlit LCD touchscreen
  • Hot water capacity with an average flow rate of 18 L/min
  • Available in outputs ranging from 4.7 to 35.0kW
  • Hot water performance comparable to an installed 150L cylinder
  • Dials that are easy to use for quick adjustment of heating or hot water
  • The Viessmann 111-w is Energy efficiency class A
  • A wireless remote control is an option
  • Optional solar thermal backup
  • Extended warranty up to 10 years available for Boilerhut

Read more in our Viessmann-111-W Storage Combi Boiler Review

Vaillant ecoTEC plus Combination Store

The Vaillant combi boiler comes with a hot-tank from Vaillant and delivers outstanding performance at a lower cost. The boiler produces 20 litres of hot water per minute when it is needed. It then modifies to use only 16% power, which saves you money and fuel.

Vaillant ecoTEC plus Combination Store Key Features

vaillant ecotec store combi boiler
  • Rated for heating efficiency and hot water, ErP A
  • Dimensions (HxWxD): 720mmx440mmx600mm
  • An integrated hot water storage device is located at the back the boiler
  • Hot water in 5 seconds
  • Up to 20 l/min flow rate
  • There are many heating control options available
  • Vaillant Advance Installers offer a 5-year standard guarantee, and 7-10 years if you choose to upgrade.

The Vaillant boiler is thicker than the Viessmann. Because there are so many options available, it is important to measure your home and talk to a heating specialist before you buy a boiler.

Viessmann Vitodens 222-f floor standing storage combi boiler

The Viessmann Vitodens 222F floor-standing gas storage combi boiler is designed to provide heat and hot water to larger homes through its 100-litre hot tank.

Vitodens 222F is designed to fit easily into a kitchen. Its standard dimensions allow for easy integration.

viessmann vitodens 222-f storage combi boiler

Viessmann Vitodens 222-F Key Features

  • Rated heating output: 1.8-35 kW
  • Integral loading cylinder
  • Inox-Radial stainless Steel Heat Exchanger
  • Modulating Matrix Cylinder Burner
  • Thermal insulation for a 100-litre cylinder
  • Compatible with ViStart and ViCare apps by Viessmann

Touch-screen in colour with graphic representation of energy consumption

  • No LPG conversion kits are required
  • Installed by Viessmann-trained installers, 10-year warranty

Storage combi boiler installation quotes online

Most local boiler installers can install one of these boiler systems. You can get free boiler quotes on these wall-mounted beasts in under 10 seconds online now with one of our recommended local Gas Safer registered heating engineers. If you want a more conventional combi boiler, then check out some of the best combi boilers we have right now.

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