Deciding on the right boiler model to go for when you need to have a new one installed can be tricky. Before you ask for advice on which boiler model would be the best fit for your home, it’s a better idea to understand what the differences are between a conventional boiler and a combi boiler for yourself so that you can make an informed decision when it comes to it. 

In this post, we’ll provide you with a comprehensive guide about combi boiler vs conventional boiler models. By the end of the post, you’ll understand exactly what each of the models is, get a good overview of the advantages and disadvantages of the two boiler types, and learn how to assess which model will fit into your home better.

Combi Boiler vs Conventional Boiler

When it comes to making the decision of whether to go for a combi boiler or a conventional boiler, you need to understand the key differences between the two types and how they differ in functionality, and how they are installed. 

What is a Combi Boiler?

A combi boiler is the shorter name given to a combination boiler. The name is given to this kind of boiler as the boiler acts as a central heating system as well as a system that heats your water supply. The water is also heating from the mains, which means there is no need for you to have a bulky water tank in the room, taking up extra storage space. Hot water is also heated on demand, given that there is no storage unit that stores the hot water for you. 

If you have a smaller home, a combi boiler is definitely the best solution for you because of its space-saving qualities. The boiler also allows the water to be powered by the mains, which ensures that the water pressure in the main areas of the house, like the bathroom and the kitchen is more than enough. 

Combi boilers can also be powered by either electricity or gas, which means they are very efficient and have the potential to save you a lot of money on energy bills. The fact that they heat water on demand also means they use up less energy than having to heat an entire tank, so in smaller homes, they are usually the better option. 

What is a Conventional Boiler?

A conventional boiler, or a regular boiler, is a heating system that uses hot water from a tank to heat the rest of the home. When hot water is required, either for the heating system or for a hot water tap, water is fed from the hot water tank into wherever it is required. 

The tank is also usually kept at height in order for you to get the most out of the water pressure possible. Having the tank kept in a physically higher location assists in increasing the water pressure. 

These boilers are usually better suited for bigger homes given the fact that the large storage tank usually heats rough water to supply larger households. It’s also easier to heat one lot of water at a time and then feed hot water from there instead of heating little amounts of water at a time every time the hot water taps are turned on. 

Key Differences between Combi and Conventional Boilers

As discussed, the main difference between a combi boiler and a conventional boiler is the way in which they are set up. A combi boiler heats the home and hot water through a single, compact system. On the other hand, a conventional boiler has a hot water tank and a cold water tank. Cold water is heated in the hot water tank and then fed through to wherever the water is required. 

You, therefore, do not need to wait for hot water with a combi boiler because the hot water is heated on demand. With a conventional boiler, you must wait for the hot water tank to heat up before you can get hot water again. 

Combi boilers and conventional boilers also differ in the amount of space they take up, with combi boilers taking up significantly less than conventional boilers. They also differ in the way they generate water pressure, with combi boilers using electrical or gas-powered mechanisms to provide adequate pressure, but conventional boilers use gravity to generate water pressure for the home. 

The two models also differ slightly in costs, with the installation costs usually being lower for combi boilers because there is physically less equipment to install. Conventional boilers need to have the heating system and the two water tanks installed and, therefore, can cost more. However, depending on the hot water demand of the home, it can also be more expensive to run a conventional boiler than a combi boiler. 

Advantages and Disadvantages

As with any model of boiler, here are the advantages and disadvantages of having them installed in your home. Let’s take a look at the advantages and disadvantages of combination versus conventional boilers. 

Advantages of Combi Boilers

Combi boilers are usually highly efficient in their operation. This is for two reasons, namely that they can be powered using either electricity or gas and secondly that they heat water on demand. If they are used in a smaller home, then they are usually the more efficient option. 

For this reason, they are also more cost-effective but are also less costly to homeowners given the fact that they are far easier to install than conventional boilers, given the fact that there is only one unit to be installed. 

Combi boilers are also a popular option for those who want to install a new boiler, as they take up far less space which can be used for more storage space. 

Disadvantages of Combi Boilers

Owing to the fact that combi boilers are a newer, improved boiler model, there are very few disadvantages to having one of these installed in your home. The main disadvantages come from the exterior factors affecting the boiler installation. Firstly, these boilers run off the mains. Therefore the water pressure in your home is determined by whether or not the mains have sufficient power to produce enough pressure. 

Although these boilers are great for saving space, they also do not have a water tank, meaning if the boiler breaks down, you will have to replace the entire unit, and you will be without hot water for the length of time it takes to repair. 

Advantages of Conventional Boilers

Conventional boilers are the ideal solution for larger households as the hot water tank is usually big enough to supply water to the entire home. If the boiler breaks down, you can also rely on the hot water tank to supply your hot water while the boiler unit undergoes repairs. 

These boilers are also usually better for older properties as they are easy to plug into older heating systems, meaning you will not have to replace the entire heating system when you upgrade your boiler.

Disadvantages of Conventional Boilers

Conventional boilers tend to take up a lot of space in the home, which is part of the reason why many people keep them in places like the loft or the attic. They also rely on gravity to supply sufficient water pressure to the household, so having them kept at height helps with this too.  

Hot water is also not supplied instantly and you have to wait for the hot water tank to heat up before you can access hot water. This is frustrating if the entire hot water tank capacity is used. 

Owing to the more complex system, the conventional boiler models are more difficult to install and therefore take a lot more time to set up.

Which is Better: Combi or Conventional Boiler?

If you are looking for a new boiler and worried about whether or not a conventional boiler or a combi boiler is the better solution for you, then you should base your decision on the size of your house. Conventional boilers are usually better for larger households as they are usually more efficient because they only have to heat a single tank. Heating water on demand, as with a combi boiler, in a larger home can cost more. 

However, for newer builds that only have an electricity supply and that are only built for smaller families, combi boilers are the better option as they do tend to be more efficient and also take up less space. Saving space in a smaller household is important as you can use it for other storage purposes.


By now, you should have a better idea about the key differences between a conventional boiler and a combi boiler. Both of the boiler models certainly have their place in home installations. However, this very much depends on the size and age of your home. 

Both types of boiler are also readily available on the market, but you also will need to take into account the amount of time you can spare when having a new boiler installed. If you require more advice on conventional vs combi boilers, don’t hesitate to contact your nearest plumbers.

Get in Touch

If you want to get advice on boilers that you can trust, contact the friendly team at SD Plumbing & Heating today. Our team of gas-safe trained experts is always willing to offer you expert advice when it comes to your boiler installations. We have good relationships with boiler suppliers and are also able to offer installation and servicing for all your boiler needs.