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Last updated: 13 March 2024

Changing From Conventional Boiler to A Combi: Costs & Tips

Changing to a combi boiler

Replacing an existing conventional boiler with a combi can drastically improve the quality of heating and hot water comfort in your home. 

Removing the old conventional boiler and fitting a newer combi model does take some time and careful planning. However, once completed, you can enjoy a more efficient heating system that delivers heat and hot water much faster, with less fuel being consumed as it does so. 

In this article, we'll explore all the reasons you should consider this boiler swap, what's involved in the installation process, and the best ways you can save when choosing between installation companies. 

In fact, Household Quotes has the perfect solution for anyone looking to land a good boiler installation deal. Rather than spending countless hours researching who the best installers are in your area, checking their credentials, and waiting for them to provide you with quotes, our speedy service can provide you with multiple quotes in a few simple steps. 

Start by filling in our form, and then within 48 hours, you'll hear back from up to 3 installers from our vetted network. With multiple professional quotes to compare, you are primed to find the best deal possible. All the installers in our network are pre-vetted by our team, and we will only connect to those based in your local area. 

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Why change to a combi boiler?

There are several reasons to consider a boiler replacement. Before delving into the advantages of a combi boiler over a conventional boiler, let's look at the benefits of a new combi boiler more generally: 

Energy efficiency

Upgrading to a new boiler brings about a significant improvement in energy efficiency. Combi boilers directly heating cold water from the mains, eliminating the need for constant hot water storage which requires significantly more energy to maintain. This not only minimises energy waste but also helps you earn savings on your energy bills.

Cost savings

Opting for a new boiler replacement can bring in some substantial financial benefits. By swapping out your outdated conventional boiler with a modern and highly efficient combi model, you can gain savings of up to £540 annually on your annual energy bills (Energy Savings Trust, as of October 2023). 

The advanced technology of condensing boilers ensures they consume less fuel, resulting in reduced central heating costs for your home. 

Environmental impact

A new boiler replacement journey not only benefits your wallet but also helps reduce your home's carbon footprint. The increased efficiency of new condensing boilers results in lower overall fuel consumption which help minimise your environmental impact. 

Condensing boilers are the standard for new boiler across the UK. These boilers come with at least 92% efficiency. This means for every pound you spend on heating costs, only 8p will be lost in waste gases. Compared to an old G-rated boiler with 70%, new condensing boiler are at least 17% more efficient. 

What is a combi boiler?

A combination, or just "combi", boiler delivers hot water through your central heating system to provide heat and hot water as and when you need it. Combi boilers provide water directly from the mains supply and heat it on demand. 

These are the most commonly found boiler types throughout the UK because they operate entirely from one unit and do not require any additional units. 

This makes them easily installed and spatially efficient. In fact, their compact dimensions make it possible to keep them neatly in a standard kitchen cupboard. 

Combi Boiler Square

Advantages of combi boilers

Compared to a conventional boiler, there are several advantages that a new combi boiler can offer you. 

  1. Fewer components

Combi boilers consist of one compact boiler unit, whereas a conventional boiler comes with an additional hot water cylinder and a cold water cistern. With fewer components, you can expect a speedier and more cost-effective installation. In terms of ongoing maintenance, combi boilers are also more straightforward to service and maintain. 

Combi boiler
Conventional boiler
  1. Space-saving

Combi boilers come with a compact design, often fitting inside standard kitchen cupboards. This space-saving feature eliminates the need for hot water storage cylinders and cold water tanks that come with conventional boilers. The absence of these components saves space within your home. This is especially useful for those in smaller homes where space is precious. 

  1. Instant hot water

Combi boilers provide hot water on demand. With conventional boilers, you may encounter delays in hot water delivery when the storage tank is refilling. However, with a combi boiler, this shouldn't ever be a problem, as long as your local mains supply is reliable.

  1. Energy efficiency

Combi boilers are highly energy efficient because of their direct mains supply, meaning they only heat the required amount of water. This results in cost savings on energy bills and annual running costs. On the other hand, regular boilers use more energy because they store hot water and work to keep it warm even when you're not using it.

  1. Reliable hot water flow rate

With a combi boiler, you can count on a dependable hot water flow rate. Unlike conventional boilers that rely on gravity to deliver water from a cold water tank, combi boilers ensure a consistent and efficient hot water supply without the fluctuations associated with gravity-fed systems. This is because combi boilers provide water at mains pressure.

While there are many advantages to choosing a new combi boiler replacement over a conventional model, this kind of boiler swap will likely cost considerably more than a like-for-like replacement. To help you save on installation, use Household Quotes to get the best deals in your area.  

We can provide you with up to 3 professional boiler replacement quotes from the most suitable options from within our vetted network. You are then free to compare their quotes and choose the one that offers the best deal for you. Getting your quotes directly from us saves you all the countless hours that it would usually take to scour the internet for the best options in your area on your own. 

Our service is free, fast, and comes with no obligations. Get started today by clicking the button below. 

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Considerations when replacing a conventional boiler with a combi boiler

Here are some important factors to consider before deciding to install a new combi boiler. 

  1. The size of your home 

Combi boilers are most suitable for smaller homes with less energy demands. While some combi boilers are powerful enough to supply for large homes, these models are generally more energy intensive and come without any hot water storage. Therefore, you may be better off with a system boiler. 

Another option to consider is a storage combi boiler. Functioning similarly to a traditional combi boiler, it stores hot water in a cylinder, creating a hybrid of combi and system boilers. 

  1. Fuel type 

Combi boilers are typically run on gas, oil, LPG (Liquified Petroleum Gas), or electricity. When it comes to running costs, oil boilers currently offer the cheapest heating of these options. However, in terms of upfront boiler costs, oil fired boiler prices are the most expensive. 

As shown below, opting for an electric combi boiler will result in higher energy costs compared to a gas-fuelled one.

Fuel price UK
Fuel typeGasOilLPGElectricity (standard rate)
Average price (pence/kWh)12.077.2811.1227.35
Source: Energy Savings Trust

What is involved in changing to a combi boiler?

Converting your conventional boiler to a combi can be a somewhat lengthy process, at least when compared to a straightforward like-for-like boiler swap. That's because swapping your boiler for one of the same type often means that the surrounding pipework and external units can stay in place.

The process of swapping a conventional boiler for a combi can be summarised into the following steps.

Change to combi boiler

How long does converting to a combi boiler take?

As we mentioned earlier, swapping to a new type of boiler adds some time and complexity to your boiler replacement. While a straight forward boiler swap takes about a day, swapping your conventional boiler for a combi will likely add another days work. Therefore, you can expect the whole process to take 1-2 days

One way to make sure the boiler replacement goes as smoothly as possible is to try and clear the space around the boiler and the external units as much as you can before the engineer arrives. 

You should also install the new boiler in the same location as the previous one, otherwise you could risk adding more days to the installation process. Therefore, moving your boiler to a new location is not advisable unless absolutely necessary. 

How much does a boiler conversion to combi cost?

Combi boilers prices in the UK typically range from £500 – £3,000, before installation. Installation costs, which will usually range from £1,500 – £2,500 for a boiler conversion, bring the total costs for a conventional-to-combi boiler replacement to £2,000 – £5,500.

How much is a new combi boiler?
Cost excluding installationCost including installationAverage, inc. installation
£500 – £3,000£2,000 – £5,500£2,750

Compared to conventional or system boiler prices, combi boilers tend to be less expensive. New boiler prices vary depending on the boiler size, model, brand, and warranty length. 

To find out more about prices offered by some of the most popular and reputable boiler brands in the UK, check out our dedicated boiler brand pages:

A boiler swap to a new type of boiler will usually cost more than a like-for-like swap since it requires considerably more time to remove the external units and specialist labour to adjust the surrounding pipework. 

Generally, installation rates are determined by the companies installation rates, which can vary depending on the size of the company and their location, relative to yours. 

Want to convert your conventional boiler to a combi boiler?

Before handing over your project to an installer, it's important to compare numerous options by checking the credentials of at least 3 different companies, reading previous customer reviews, and requesting tailored quotes. By doing so, you can be sure that you've found the best possible option that offers quality parts and labour as well as a good deal.

However, the process of finding multiple reputable options and reaching out to them for quotes can be time-consuming, requiring hours of research. That is unless you get your quotes through Household Quotes.

Using the information you provide in our quick 30-second form, we can provide you with up to 3 quotes from the top-rated installation companies in your vicinity. All of the installers in our network are Gas Safe registered and are vetted by our team. We will only connect you with the most suitable options in your local area, allowing you to benefit from the best local rates.

Click the button below to get your free, no-obligation quotes.

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