Cheap New Boiler Replacement and Installation Costs 2021

new boiler installation
Credit: Worcester Bosch

Is it time to replace your current boiler?

It might be if, lately, you’ve heard it making strange sounds, there are cold patches on your radiators when they should be warm, or you’ve noticed your gas bills rise in recent months.

So are you considering swapping your old boiler for a new boiler, and are you always on the lookout for a bargain?

If so, you might want to look at the cheapest new gas boilers in the UK at the moment, and how they compare against the more expensive market leaders.

In this article, HomeSage covers:

  • what a combi boiler is – and why you should go for one
  • what to look for when choosing a cheap combi boiler
  • the top 10 least expensive boilers for small, medium, and large properties
  • how much a boiler costs to install
  • the most commonly asked questions about cheap combi boilers

Nothing brings down prices like competition and we’re pleased to report that HomeSage users have reported savings of up to 54% on their boiler supply and installation costs by using our service. How do they make these savings? 

Just fill in the form anywhere on this page and we’ll send your details to three or four established local installers.

They’ll find out what you need your boiler to do, recommend a system, and leave you with a quote. Our service is free and there’s no obligation to accept any offer made by a partner installer.

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What is a combi boiler?

Credit: Worcester Bosch

There are three types of boilers most commonly installed in the UK – combi boilers, regular boilers, and system boilers.

Regular boilers and system boilers rely on the installation of one or two water storage and heating cylinders to operate.

The problem with this is that, as UK houses are some of the smallest in the world, not many people live in properties large enough to warrant having one, let alone having the space required for the extra tanks.

A combi boiler system, unlike a regular or system boiler, is actually an all-in-one unit.

In this article, therefore, we’re looking exclusively at Britain’s cheapest combi boilers.

Most combi boilers simply draw water from the mains when you or a member of your household wants hot water or heating.

The water drawn from the mains then passes through an exchanger which heats up that water on demand – it’s like one of those instant-boiling taps which heats the water as you’re pouring it into your cup.

A few combi boilers have a water storage tank installed inside them as well as a heat exchanger. These types of boilers are really only suitable for the very largest properties though.

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What to look for when choosing a cheap combi boiler

new boiler quote
Credit: Worcester Bosch

An installer will visit you ahead of giving a final quote.

They will recommend which boiler unit you should choose, based upon how big your home is and how many bathrooms, bedrooms, and radiators are in your property.

Although every property is different, installers will recommend a combi boiler with the following “output levels” on the following criteria:

Property sizeBedroomsBathroomsRadiatorOutput recommendation
Small1-21up to 1224kW-27kW

The “output” is the amount of energy a boiler uses to heat the water which passes through it.

The larger your property, the larger the output level you should select.

You should also consider the “flow rate” – this is how much water can actually pass through your boiler measured in litres per minute.

The higher the flow rate, the more water your boiler can pass through to the exchanger to heat it up.

A higher flow rate means that if two or more people are using hot water taps at the same time, the chances of both taps losing pressure, or the water not being hot enough, decreases.

Please bear in mind that your mains water pressure is also a factor on the amount of water your boiler can process.

If your boiler has a flow rate of 14 litres per second but the water pressure equivalent of the mains is 12 litres per second, your actual flow rate will be that of the mains water.

Another important factor is a boiler’s environmental efficiency.

Each boiler is graded from A (the most environmentally efficient) to G (the least).

The more efficient your boiler, the more energy it uses on the heating of water and not other operational functions and the less you pay on your gas bills.

Finally, the dimensions of your boiler. One of the reasons why combi boilers are so favoured by UK homeowners and landlords is that they are generally so small and easy to conceal.

Where do you intend for your installer to fit your combi boiler?

Let him or her know if you want it hidden in a cupboard in the kitchen or the bathroom so that they can recommend a boiler which will fit snugly in it.

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The top 10 cheap boilers for smaller properties

Credit: Worcester Bosch

On the market right now, there are seventy seven gas-powered combi boilers available to choose from with an average price of £1,035 before installation.

The boilers listed below are around half that price and their HomeSage scores are impressive given the complexity of equipment inside each piece of machinery.

What is the HomeSage score?

This is an exclusive grading system unique to this website which assigns each boiler a percentage rating based upon a number of important factors including price, warranty length, energy efficiency, and more.

Make and ModelEfficiency RatingParts and Labour Warranty (months)Output kWFlow RatePrice fromTOTAL
Vokera Easi-Heat Plus 25Ci Boiler93.00%602510.2£44082.21%
Biasi Riva Plus ErP 24kw Boiler88.00%242411.6£51576.15%
Glow-worm betacom4 24kw Boiler89.20%602410£51582.08%
Ravenheat WH80 25kw Boiler90.30%602510.2£51579.88%
Ravenheat WH90 30kw Boiler90.30%602512£51579.88%
Ravenheat CS80 25kw Boiler90.30%242511.9£53577.34%
Vokera Compact 25A Boiler89.10%242510.2£53576.97%
Ravenheat CSI 120 25kw Boiler92.00%362513.2£54078.16%
Ariston E-One 24kw Boiler90.00%242412.1£56575.89%
Intergas Rapid 25kw Plus Boiler93.00%722515£58082.81%
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Honourable mentions

What are our highest scoring boilers in this category?

The Worcester Bosch 2000 25kw boiler is our top performer with a score of 91.89% and it’s just £180 more expensive than the 10th cheapest boiler on our chart.

Make and ModelEfficiency RatingParts and Labour Warranty (months)Output kWFlow RatePrice fromTOTAL
Worcester Bosch 2000 25kw Boiler93.00%60259£76091.89%
Baxi 624 Boiler89.00%842410.2£72090.56%
Baxi 424 Boiler89.00%60249.8£61589.15%
Baxi 224 Boiler89.00%36249.8£62087.47%
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The top 10 cheap boilers for medium-sized properties

Credit: Worcester Bosch

There are 80 gas-powered combi boilers available for medium-sized properties with an average selling price before installation of £993.

As you can see from our chart below, there are some significant savings to be made with our cheapest boiler achieving a higher HomeSage score than the nine other boilers on the list.

Make and ModelEfficiency RatingParts and Labour Warranty (months)Output kWFlow RatePrice fromTOTAL
Vokera Easi-Heat Plus 29Ci Boiler93.00%602911.9£46582.15%
Biasi Riva Plus ErP 28 Boiler88.00%242813.6£51576.15%
Glow-worm betacom4 30 gas boiler89.20%603012.4£55581.98%
Alpha EVOKE 28 Boiler88.90%602812.1£56570.46%
Ravenheat CS90 30 Boiler90.30%243014£58077.23%
Alpha EVOKE 33 Boiler89.00%603314.1£58070.42%
Ariston E-One 30 Boiler90.00%243014.5£59075.82%
Vokera Compact 29A Boiler89.00%242911.9£60576.79%
Vokera Easi-Heat Plus 32Ci Boiler93.00%603212.9£61081.79%
Biasi Advance Plus ErP 30 Boiler88.60%603016.2£61578.41%
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Honourable mentions

The mid-sized boilers finishing the highest measured by our HomeSage ranking system are only marginally more expensive than the boilers which make up our top 10 list.

Make and ModelEfficiency RatingParts and Labour Warranty (months)Output kWFlow RatePrice fromTOTAL
Baxi 428 Boiler89.00%602811.5£64091.59%
Baxi 228 Boiler89.00%362811.5£62087.47%
Intergas Rapid 32 Plus Boiler93.00%723218£63082.69%
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The top 10 cheap boilers for larger properties

Credit: Worcester Bosch

For the biggest properties, the leading UK manufacturers produce a range of 49 different gas-powered combi boilers with an average price before installation of £1,370. The top four boilers in our list are actually under half that price.

Make and ModelEfficiency RatingParts and Labour Warranty (months)Output kWFlow RatePrice fromTOTAL
Ferroli Energy Top W60 Boiler98.00%24656.97£59078.09%
Biasi Advance Plus ErP 35kw Boiler88.60%603519.2£63578.36%
Ferroli Energy Top W80 Boiler98.00%24757.94£67577.88%
Biasi Inovia ErP 35kw Boiler88.60%603519.2£68080.75%
Ariston CLAS HE evo 38kw Boiler90.00%603815.6£73577.97%
Glow-worm Ultimate3 35kw Boiler89.70%1203514.4£76085.64%
Ferroli Modena 38c HE Boiler90.30%603821.8£83079.98%
Ariston E-COMBI evo 38kw Boiler90.10%243815.6£88075.11%
Viessmann BPJD Vitodens 050-W 35kw Boiler89.00%363514£89077.79%
Glow-worm Energy 35kw Boiler89.20%843514.4£89582.81%
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Honourable mentions

And the boilers finishing top of the HomeSage ranking are all at least £400 below the average supply-only price – indicative of a healthy marketplace with lots of competition.

Make and ModelEfficiency RatingParts and Labour Warranty (months)Output kWFlow RatePrice fromTOTAL
Baxi 636 Boiler89.00%843615£97592.43%
Potterton Titanium 40k Boiler91.10%844016.4£91579.57%
Vokera Unica i36 Boiler89.20%603614.7£90078.57%
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How much does a boiler cost to install?

Credit: Worcester Bosch

Now you know the prices of the cheapest gas combi boilers, you’ll now need to save for installation and other costs connected to the fitting.

A good rule of thumb to use in assessing the likely budget you’ll need to set aside is as follows:

What you might see on your quotePrice range
Boiler installation cost£630-£780
Cost of moving pipes£190-£310
Mechanical flush before installation£440-£535

New radiators/radiator replacement – £325 to £410 per radiator

You may wish to add extra radiators to your property or replace any existing ones to bring them into the general aesthetic styling of your home.

Each radiator will cost in the region of £325 to £410 across manufacturers’ standard ranges. Don’t forget that you will need to also budget in an hour or two’s labour charges for each new radiator you install or existing one you replace!

Piping work – £190 to £310

Most boiler replacement jobs involve removing an existing boiler and installing the new one in the very same place in your home.

If you decide that you want to replace your boiler and have its replacements installed in a different location around your property, there will be additional piping work for your fitters to carry out.

Likewise, if you are installing new radiators into your property at locations where no radiators are currently located, they will need piping to your new boiler too.

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Mechanical flush – £440 to £535

For very old boilers, particularly those which have been in constant use for a decade or more, an installer might recommend that you perform a mechanical flush. This helps you get the very best value out of your new system. This is sometimes referred to as a powerflush.

Why would a mechanical flush be needed and what does one do?

Since the time your current boiler was installed, water has constantly moved around the system and this movement creates rust and other debris which hinders the movement of hot water through your pipes and to your radiators and taps.

It means that your boiler has to work a lot harder to do the job it’s meant to do well.

Your home will not be benefiting from the smooth and constant delivery of heat and hot water you and your family want with your cheap new boiler.

It will also push up your gas bill each quarter.

If you have any of the following issues, please let your installer know and ask him or her to include the cost of a mechanical flush on your quote:

  • your pipes are hot but your radiators are cold
  • you find yourself having to restart your boiler a lot
  • your boiler makes a lot of noise when it’s in use
  • some radiators are hot while other radiators are just warm or even cold.

Programmer and thermostats – £150 to £225

Credit: Worcester Bosch

Modern domestic heating is much more sophisticated than it’s ever been because of its increasing integration with the “internet of things”.

Because they’re now connected, you can better control the temperature of your home and individual rooms in it using everything from control panels to mobile phone apps.

Thermostats are more connected than ever before.

You can tell your thermostat to stop providing hot water to radiators within a room if it gets too hot or you can tell it to provide more hot water if it starts to feel chilly.

In the past, thermostats really only controlled the overall temperature in your home but now you can ask your installer for individual thermostats for each room.

A programmer works differently to a thermostat.

Central heating programmers allow you to stop and start hot water and heat provided by your boiler on select days and times – they’re very easy to programme too even if you’re not confident with technology.

Adding thermostats and a programmer to your boiler installation should cost between £150 and £225.

Thermostatic radiator valves (TRVs) – £15 to £25 per radiator

You may already have thermostatic radiator valves in your home but, if you don’t, they’re worth considering at £15-£25 a time.

TRVs are another way to control a room’s temperature – they do so by changing the amount of water flowing to a radiator within a chosen room.

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Cheap new boilers – FAQ

boiler after care service
Credit: Worcester Bosch

Why do people get a new boiler?

According to Energy UK, even newer and more energy efficient boilers can take 60% off your energy bill.

If your current boiler is 10 years old or more, then that percentage can be even higher.

In addition, although boilers manufactured a decade ago were state-of-the-art, many of them will now require regular maintenance – an extra expense on top of what are already too high gas bills incurred as a result of using them.

What are the disadvantages of combi boilers?

The three main downsides to buying a new combi boiler are:

Water pressure

Despite the expertise and experience your installer brings to making a choice for the right boiler, they can do nothing about the pressure of the water coming into your home.

Sometimes, using two hot taps or more may mean that the water pressure to each tap drops as well as the temperature.

If you want hot water coming out of multiple taps at the same time at a reasonable pressure, you might want to choose a regular or system boiler instead if you have the space.

System failure

If your system breaks, you’ll be left without both hot water and central heating.


Combi boiler replacement parts are expensive.

Ideally, you should choose a boiler whose manufacturer provides a long and generous warranty on their products.

Should my installer have any particular qualifications?

Credit: Worcester Bosch

All boiler engineers must be Gas Safe registered – before going ahead with a particular installer, check that they are approved for the work on the Gas Safe Register website

If you use a heating technician, you might also want to check if they are OFTEC accredited and MCS certified.  

If you get your quote through us, you can be assured that all of our partners and their installers are fully Gas Safe Registered.

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How long does it take to fit a new boiler?

If your new boiler will go in the same place in your home as the existing boiler, the whole job should take about a day.

When you want to install it in a new location in your home, you should budget for 2-3 days’ worth of disruption to your home because of the need to cap existing pipework and install additional piping.

In some cases, your engineer may also need to change piping to your radiators.

If you want to swap one type of boiler for another (for example, switching from a regular boiler to a combi boiler), this may take about 3-5 days because of the need to remove the water and/or heating cylinders and lay new pipework.

As mentioned above, an installer may recommend a mechanical flush for your radiator system.

Check out our article on how long it takes to fit a new boiler for more info.

Getting yourself the best boiler deals

Getting a new boiler is a big investment for any household so make sure that you ask all the questions you need to before going ahead with any quote.

We understand that homeowners and landlords want to save money and we feel that it’s important, as an impartial website, to show you the full range of boilers available to you, particularly if you are on a budget.

Fill in any of the forms on this page and we’ll contact three to four local Gas Safe installers to quote you.

Competition maintains service levels and product quality but it reduces prices. Many HomeSage users have reported to us a difference of up to 54% between their highest and lowest quotes so it always pays to shop around.

Our service is free and you’re not obliged to accept any offer made by one of our partner installers.

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Andy is one of the HomeSage founders and an occasional content contributor. His love for boilers is only just outweighed by his love for football.