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Combi Boiler Conventional Boilers Better

When you are about to purchase a new boiler, it is important to know about the different types of boilers and how they work. Most of the households get the choice to switch from their conventional boiler to a combi boiler. If this sounds familiar, understand your options before you do anything else.

In order to make a better decision, you should know how a combi boiler and a conventional boiler work. Also, what are their pros and cons?This post explains the combi boiler and conventional boiler in detail for all beginners.

What Is a Combi Boiler?

A combi boiler is short for a combination boiler. It is a combination of a water heater and the central heating boiler system in a single unit. As soon as you turn on the hot water tap, it heats hot water on demand. This eliminates the need for a storage tank.  Storage tank required in the case of a conventional boiler.

How Does Combi Boiler Work?

Combi boiler is one compact system without any external cold-water tank or hot water cylinder. Combi boiler heat water and warm home through radiators. Combi boilers provide instant hot water, by constantly being on standby. As soon as you turn the hot water tap, the boiler will start and the hot water will available immediately.

When some open the hot water tab and request hot water, this will signal the boiler to start heating water inside of the system and hot water supply begin quickly. The heat exchanger inside the combi boiler will transfer the majority of the heat from the burnt gas inside the boiler to the cold water, make it hot, and then delivers the hot water to taps as required.

Inside the combi boilers, the control valves operate in different directions. These valves either allow water to flow through the central heating system or divert it to the hot water tap as required. Combi boiler can’t do both at the same time. You can also pre-set your desired temperature and the boiler will work with the room thermostat to ensure your home will heat, as you like.

Pros of Installing Combi Boilers

Combi boilers are the most popular choice of modern households in the UK because they offer the following advantages:

High Efficiency: Combi boilers are highly efficient. You can save money on your heating bills by switching from a conventional boiler to a combi boiler.

More Affordable: The installation cost of a combi boiler is low as compared to a traditional heating system. Combi boiler parts are easy to find as well. The whole combi boiler system is less complex, and few manhours are required to install them.

Faster & Quick Operation: Combi boilers are faster than the convention boiler. There is no need to wait to get hot water. You will get the unlimited supply of hot water on demand.

Less Space Requirement: Combi boilers are compact in size. They don’t have a separate cold & hot water storage tank. This makes them ideal for small homes.

Clean Water Supply: As the water is directly supplied from the mains and it is not stored in a tank, you don’t have to worry about built-up sludge. The water that runs through the taps will be much cleaner.

Safe to Drink Water: The cold water supplied by the combi boiler is safer to drink. There is no storage tank involved and the water comes directly from the mains supply makes it safer for drinking.

Fewer Pressure Issues: You won’t have to worry about air locks or low pressure when using a combi boiler system. The hot water comes from the mains directly.

Cons of Combi Boilers

Combi boilers are popular but they also have a few issues that you should be aware of.

Depends on Mains Pressure: The combi boiler works properly when the pressure at the mains is good. Before getting a combi boiler installed, it is a good idea to get the pressure in the mains tested.

No Water Tank: Combi boiler doesn’t have a hot water storage tank that can store hot water for later. If the boiler breaks down, your house will be without hot water & heating.

What Is a Conventional Boiler?

Also known as, a traditional boiler, a conventional boiler is a heat-only boiler. Mostly older homes have these because they fit into the design and structure of the property. The boiler is attached to the traditional heating and hot water system of the house.

How Does Conventional Boiler Work?

A conventional boiler has two tanks. One is a cold-water supply tank that feeds the water and another is a hot water storage tank. Water is supplied through a cold water supply tank, heated and then stored in the hot water tank. To keep the house warm, the water from the hot tank pumps around the central heating system.

Since it stores hot water, the whole house gets a consistent supply of hot water as and when needed. The boiler does not rely on pressure from the mains. Conventional boilers are suitable for homes that have storage for hot and cold-water tanks.

Pros of Conventional Boiler

These pros explain why conventional boilers are still used in so many households:

Store Hot Water: If your boiler breaks down, you will still get hot water supply. You can also install an immersion heater in the hot water cylinder to heat water.

Enough Hot Water for Multiple Users: Even if multiple taps are open and in use of hot water, there is no need to worry. It does not affect the temperature or water pressure. Conventional boilers are best in meeting higher demands for hot water. Everyone will get hot water until the cylinder needs refilling.

Work with Old Heating System: If you have an old house with a traditional heating system, the conventional boiler will be compatible with the system. You might not have to change the pipework at all.

Cons of Conventional Boilers

Conventional boilers have some cons, that’s why they are no longer the first choice:

Space Constraints: Conventional boilers need a lot of storage space. You will need a loft for placing the water tank and need a cupboard for the hot water cylinder. In case you live in a flat or a small house, this is not an ideal option. 

No Instant Water Supply: Once all the hot water from the cylinder is consumed, you will have to wait until the tank heats the water up. This could take a while.

Frequent Heat Loss: As the cylinder stores hot water and if a cylinder is not insulated properly, it could lose heat. In other words, water will become cold very fast.

Complicated System: Conventional boilers are complicated to install. They have different parts and pipework. Installation can be time-consuming and require more manhours.

Performance Constraints: There must be a sufficient amount of pressure from the main water supply to ensure you get a steady flow of hot water in the taps. Water pressure is not always good. To increase the flow, many households install a pump. This is an extra expense.

Combi Boiler Vs Conventional Boiler – A Brief Comparison

Take a look at this comparison between a combi boiler and a conventional boiler. This will help you decide which one’s better:

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Should I Replace My Conventional Boiler with a Combi Boiler?

If you have a small home, a combi boiler would be an ideal purchase. When you are moving into a new house and carrying out extensive renovations, it is a good time to have a new heating system installed as well.

The most common reason that users switch from conventional to combi boilers is energy efficiency. According to Energy Saving Trust, you can save up to 40 percent on your energy bill if you replace your 10 to 15 years old boiler with an A-rated combi boiler.

The efficiency of your old boiler can come down from 70 to 50 percent over the years. You will be losing £30 to £50 of every £100 you are spending on energy bills.

Switching to a combi boiler can save you not just the bill, but a lot of trouble. The boiler produces hot water on demand. A conventional boiler certainly stores hot water in the tank but eventually, the water cools down. You have to turn on the boiler again to heat the water. This wastes a lot of extra energy. A combi boiler, on the other hand, works only when hot water is required.

Is Combi Boiler Worth It?

Whether a combi boiler is worth it depends on the needs of the consumer. When you switch to combi, you get rid of cylinders, tanks, and extra pipework. You will have a lot of free space in your house.

If your hot water requirements suit a combi boiler, it is certainly worth installing it in your home. Even if you have a large house with 2 to 3 bedrooms, you can find a boiler that can handle high flow rates. This would ensure everyone gets a sufficient supply of hot water whenever you need it.

How Do I Know Which Boiler is Right for Me?

A few factors can help you determine which boiler is suitable for your home:

Available Space: The amount of space available in your property will tell which boiler would be the right fit. If you have limited storage space and you can’t store a separate hot water tank, a combi boiler is what you need.

If you have already decided to have a larger model of a conventional boiler, you must make sure there is sufficient space to install the system.

Existing System: Do you want to keep the same system that is already in place? Chances are the existing system that needs an upgrade depending on the boiler you are planning to install. Different systems require a different amount of space. You must ask yourself are you willing to spend money on the upgrades.

Hot Water Needs: Do people living in the house demand hot water simultaneously? Along with the hot water demand, you must also take into account the available space. If you have less space and multiple users, you will need a combi boiler with a higher output. On the other hand, if you have extra space and multiple users, you can select a conventional boiler.

Number of Bathrooms: The number of bathrooms in the house will affect the size and type of boiler. The more the bathrooms, the higher the demand for hot water. Thus, you will need a large boiler.

If you have 3 or more bathrooms, a conventional boiler is a better choice. Combi boilers can provide a single water flow only. The water pressure diminishes if the flow is split between multiple bathrooms.

Combi Boiler Conventional Boilers Better


Combi boilers are compact, quick to install, and they provide hot water on demand. They don’t have storage tanks or cylinders, which makes them ideal for small homes.

Conventional boilers, on the other hand, are ideal for large households. They work with a water tank and a cylinder. You will need extra space for the cylinder and storage tank.

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