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Last Updated on January 24, 2021

Changing From Conventional Boiler To Combi – Here is How and Why

Zac Houghton

Zac Houghton

Heating expert and founder of Loftera.

From saving an average £310 on energy bills every year, to getting instant heat and hot water, and being environmentally friendly too, swapping your old boiler for a combi boiler is a no-brainer.

And it’s not as costly or as disruptive as you think. But just how do you do it? Well, here’s our four-step how to guide to help you.

Changing From Conventional Boiler To Combi

Table of Contents

How to decide if you should change from a conventional boiler to combi boiler

There are huge benefits to changing from a conventional boiler to a combi one.

It’s worth remembering that conventional boilers are often old and will need replacing at some point and they will cost more over the years to maintain and repair. Also, because they become more inefficient as they age, it means that you pay more on energy bills, up to a whopping 40% more in some cases.

Look at the age of your current boiler – the average boiler works well for 10 to 15 years – and then it is worth looking at when you need to replace it and building this into your financial planning.

It also makes sense to consider changing your boiler before you do any new cosmetic or decorative work to your home, so you don’t have to patch up any redecoration caused by its installation.

Combi boilers save the average Brit £310 annually on their energy bills and a modern combi system will also add value to your home, so the long-term financial benefits also need to be considered.

Combi boilers also give you instant heat and hot water making life more comfortable and they are better for the environment as boilers release CO2 gasses. The older and less efficient your boiler, the more CO2 it will release adding to your carbon footprint.

How to choose the best combi boiler for you

The first thing to consider is your budget, remembering to factor in that your boiler will need replacing at some point and that you will save money on future bills.

The average cost to switch from a conventional boiler to a combi boiler is between £2,700 to £3,000 which is more expensive than just replacing an existing conventional boiler but with an estimated saving of 40% on energy bills annually by making the switch, the upgrade will pay for itself.

Combi boilers heat up water straight from the mains which means you get instant hot water and heat and are 90% efficient, whilst conventional boilers heat up water in tanks which takes longer and uses much more energy, making them more expensive to run. Old conventional boilers also are cumbersome and can take up attic and other space that you can free up, again adding value to your property.

There are different sizes and types of combi boilers and what works for you should factor in the cost and size of your property.

It’s a good idea to sound out a few companies and give them an indication of how often you have your heating on and how often you use hot water. This will enable them to see the size of boiler you need and other features such as heat up times that will suit you most.

The best thing to do is get three quotes from three different firms to establish what your options are and so you can see which is the most competitive.

Check companies have the right qualifications such as being BOAS qualified and are approved to work with gas.

It is also worth checking whether they have good customer reviews and asking friends and families for recommendations.

How to swap to a combi boiler

Believe it or not, it can take as little as a day to swap your conventional boiler to a combi boiler! This does depend though on external factors such as how good the gas and electricity supply are, which could delay matters if there are issues with either.

It is a big task and one best tackled by experts as the first thing you must do is, is close off your existing boiler and pipework. This means draining the system so you will be without water and heat for this part of the process.

Ideally, you will probably want the old boiler and tank removing too, so it frees up space which is one of the major advantages of making the switch.

The combi boiler will then be installed and fitted to new or existing pipework and energy supplies. This is then tested and cleared for use on health and safety grounds and is one of the key reasons you need to bring in experts who specialise in this work.

It’s also possible to add features here such as making your new combi boiler work with a smart home by incorporating the thermostat controls with your smart phone or other smart products. This means you can run your heating and hot water remotely if you want, even through voice commands!

How to save money on switching to a new combi boiler

There are ways that you can save money if you are looking to swap your boiler to a combi one.

One way is to buy the boiler yourself looking for bargains in sales if you know what type and make you want and then you can get this installed by professionals, so you are just charged labour for that.

You should also investigate whether you might be eligible for financial help from your local authority as there are grants and benefits to help people upgrade their heating systems because this will make homes more energy efficient and less environmentally damaging.

And many companies offer finance schemes with payments from under £10 a month to make the swap, which again is a good option if you want to reap the benefits of a combi boiler but don’t have the initial investment money.

Obviously swapping your conventional boiler to a combi will save ongoing costs with up to 40% off your heating bills, as well as adding value to your home.


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