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Last updated: 10th April, 2024


Are Boiler Hot Water Storage Tanks a Necessity?

Are Boiler Hot Water Storage Tanks a Necessity?

Key takeaways

  • Storage tanks provide a steady stream of warm water, perfect for households or buildings with a high hot water demand.
  • Storage tanks may waste energy due to the nature of retaining and heating water constantly.
  • Combi boilers do not require storage tanks as they have all the components needed for a home's central heating and hot water inside the unit.

You may be wondering, are hot water storage tanks essential to home heating and the running of your boiler?

Hot water storage tanks have been a popular feature in many households for years. They allow for a ready supply of hot water and can be especially useful in households or buildings with high hot water demand.

However, some people have questioned whether these tanks are truly a convenience, particularly with the rise of combi boilers.

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What is a hot water storage tank

To start with, let's look at what a hot water storage tank is and how it works. 

Hot water storage tanks are typically used in systems where the water is heated by a boiler or other heat source, then stored in the tank until it is needed. 

This allows for a consistent supply of hot water and can be especially useful in households or buildings with high hot water demand.

Advantages of hot water storage tanks

One of the advantages of hot water storage tanks is that they can provide a more consistent supply of hot water than other systems. 

Because the water is preheated and stored in the tank, there is less of a delay when hot water is needed. This can be particularly important in larger households or buildings where multiple people may need hot water at the same time.

Disadvantages of hot water storage tanks

However, there are also some disadvantages to hot water storage tanks. One of the biggest is that they can be inefficient

Because the water is constantly being heated and stored, energy can be wasted if the tank is not properly insulated or if the temperature is set too high. 

Additionally, if the tank is too small or if the demand for hot water is particularly high, the tank may run out of hot water, which can be inconvenient.

Despite these disadvantages, hot water storage tanks are still a popular choice for many households and buildings. They can be particularly useful in areas with unreliable water supplies or in areas where there is high hot water demand. Additionally, many newer hot water storage tanks are designed to be more efficient and can help reduce energy costs.

What is a combi boiler?

A combi (combination) boiler is a type of domestic boiler that ‘combines’ a home’s central heating and hot water production into one succinct unit.

A combi takes water directly from the mains and heats it upon usage. After detecting a hot water request, the combi begins to burn gas in a combustion chamber. 

The hot gases rise and move through a series of pipes and into a component called a heat exchanger, the hot gas running through the exchanger then heats the surrounding cold water.

In a conventional boiler system, this process is done according to a programme and the water is stored in a separate cylinder until it’s needed. 

A combi only starts this cycle upon request (initiating the heating or turning on a hot water outlet), therefore the hot water is almost instant.

Advantages of a combi boiler

Compact Size

Combi boilers are popular due to their compact size and the ability to perform the functions of two appliances.

They save storage space as they are designed to be compact, fitting seamlessly into a standard kitchen cupboard and blending in with the decor.

Direct Water Supply

Combi boilers draw water directly from the mains, providing high flow pressure that guarantees a rapid and uninterrupted supply of hot water. 

Unlike conventional boilers that rely on gravity to collect water, combi boilers do not pool or heat water slowly.


Remote Control

Homeowners can remotely control combi boilers using technology such as smart thermostats or smartphone apps, offering convenience and peace of mind.


Safe to Drink

The hot water produced by combi boilers is safe to drink as it has not been stored in a tank for long periods, reducing the likelihood of contamination.


Combi boilers are cost-effective and energy-efficient to run as they primarily use gas, which is relatively inexpensive.

Quiet Operation

Modern combi boilers are designed to operate quietly, making them quieter than traditional boilers.


Combi boilers are versatile as they can run on various fuels and have abundant replacement part availability, ensuring quick and affordable repairs when needed.

That being said, combi boilers also have some disadvantages. Because they heat water on demand, there can be a delay in hot water delivery if multiple people are using hot water at the same time. 

Additionally, combi boilers can struggle to provide hot water at high pressure, which can be a problem for some households or buildings.

Despite these disadvantages, combi boilers are becoming increasingly popular, particularly in smaller households or buildings with lower hot water demand. 


In conclusion, both hot water storage tanks and combi boilers have their advantages and disadvantages. 

Hot water storage tanks can provide a consistent supply of hot water but can be inefficient and take up space. Combi boilers, on the other hand, are efficient and save space but can struggle to provide hot water at high pressure. 

The choice ultimately depends on the specific needs and circumstances of the household or building.

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Frequently Asked Questions

Does a Boiler Need a Storage Tank?

Whether a boiler needs a storage tank depends on the type of boiler system. Combi (combination) boilers heat water directly from the mains on demand and do not require a storage tank. System and conventional (regular) boilers, however, are designed to work with a hot water cylinder (storage tank) to store hot water for use when needed.

Why Do I Have a Boiler and Hot Water Tank?

Having both a boiler and a hot water tank typically means you have a system or conventional boiler setup. This configuration allows the boiler to heat water that is then stored in the hot water tank, providing a supply of hot water ready for use. It's especially useful in homes with higher hot water demands or where hot water needs to be drawn from multiple outlets simultaneously.

How Long Does a Boiler Water Tank Last?

The lifespan of a hot water tank can vary but generally lasts between 10 to 15 years, depending on the tank's material, water quality in your area, and how well it has been maintained. Regular maintenance, including inspecting for corrosion and sediment buildup, can help extend its life.

Can You Have a Hot Water Storage Tank with a Combi Boiler?

Traditionally, combi boilers are not used with a separate hot water storage tank as they are designed to provide hot water on demand directly from the mains. However, in some specific setups designed to meet high hot water demands or to integrate solar thermal systems, a combi boiler might be used alongside a storage tank, though this is not common.

How Does a Combi Boiler Work with a Hot Water Tank?

A combi boiler typically does not work with a hot water tank in the conventional sense. If a system is designed where a combi boiler is used with a hot water tank, it's usually for specific purposes, such as supporting solar thermal systems or meeting very high hot water demands. In such cases, the combi boiler provides heating, and the tank stores hot water, possibly pre-heated by another source like solar thermal panels.

Is a Combi Boiler Cheaper to Run than a Hot Water Tank?

Yes, a combi boiler can be cheaper to run than a system with a hot water tank. Combi boilers eliminate the need to heat and store a volume of water in a tank, reducing energy losses associated with heating water that isn’t used. They heat water directly from the mains when you turn on a tap, which can be more energy-efficient for homes with lower hot water demand.

What is the Cheapest Way to Run a Hot Water Tank?

The cheapest way to run a hot water tank involves several strategies:

  • Insulate the Tank and Pipes: Reducing heat loss with good insulation can significantly cut energy costs.
  • Lower the Water Temperature: Setting the thermostat on your tank to a lower but comfortable temperature can save energy.
  • Use Off-Peak Electricity: If you're using an electric tank and your energy provider offers off-peak rates, heating your water during these times can be more cost-effective.
  • Regular Maintenance: Draining the tank annually to remove sediment and checking the anode rod can improve efficiency and extend the tank's life.
  • Integrate Renewable Energy: If possible, using solar thermal panels to help heat the water can reduce the use of gas or electricity.
Stephen Day profile photo
Article by
Stephen Day | Co-founder
Gas Safe registered and FGAS certified engineer with over 20 years experience in the heating and cooling industry.