Boiler Replacements 2023 Re February 3, 2023

Boiler Replacements 2023

Boiler replacement

Why are boiler replacements a minefield?

The dreaded boiler breakdowns and inevitable boiler replacements costing anywhere between £1500-£4000 are never fun. So when it’s time to take the plunge, we’ve got everything you need to know to take some of the hassle out of buying a new boiler. This guide will talk about the options to replace your boiler and how much it will cost to get a shiny new one.

Signs you need to replace your boiler

Let’s start with the most obvious question: ‘Do you need a boiler replacement?’ We’ve compiled a list of signs you need to replace your boiler. 

If your boiler stops working and can’t be fixed, you’ll have to replace it immediately, but remember that many other less obvious signs let you know it’s time to say goodbye! Here are the six warning signs

  • An unexplained rise in energy bills – naturally, boilers lose efficiency over time, which means your energy bills will go up regardless, but if your energy bills are creeping up out of control, this might be a sign that your boiler needs replacing.
  • Your boiler makes odd noises such as banging, whistling, popping or hissing sounds.
  • Your boiler is leaking – while leaking doesn’t mean you have to replace it; it is a sign of issues in one of the internal components. We recommend calling a heating engineer to check it out before it becomes more serious.
  • Frequent breakdowns – this happens a lot towards the end of the boiler’s lifespan, and it may be time to start shopping around for a new boiler.
  • The boiler doesn’t heat your home as it used to and doesn’t provide hot water either.
  • Finding replacement parts for your boiler is a nightmare.
  • Low energy efficiency – If your boiler is less than 90% efficient, it may be worth considering a replacement to save money on your energy bills.

But before you commit to the big purchase, ask a heating engineer to check that there isn’t a build-up in your heating system stopping your boiler from working as it should.

Generally speaking, your boiler could last 10-15 years, or even longer, if it is well maintained and serviced. By this point, if it has served its time, it’s fair to say that you’ve got your money’s worth.

Should you repair or replace your boiler?

If your boiler keeps breaking down, it may be cheaper, in the long run, to cut your losses and get a new one. Imagine having to fork out £400 to repair your wonky boiler and then have to replace it the next year!

You’ll also need to remember that when you replace your boiler with a new condensing boiler, you’ll see a drop in energy bills because modern boilers are more energy-efficient. 

According to the Energy Saving Trust, you could save up to £305 per year by upgrading your old boiler to an energy-efficient A-rated boiler, which typically operates at 90% and over energy efficiency, which is obviously much better for the environment too.

What is the average cost of a replacement boiler?

Getting a new boiler quote isn’t one-size-fits-all. Boiler replacement costs vary based on many factors such as;

  • The boiler type you’ve already got
  • The new boiler type you’d like to have
  • If you’re going to convert your boiler 
  • If you want to relocate your boiler
  • If you need to upgrade your boiler pipework
  • Boiler add-ons

Other factors can also affect the cost of replacing your boiler, i.e. where you live.

Boiler swap costs

As a rough guide, these are the kind of boiler conversion prices you can expect to pay for different boiler installation types from WarmZilla, including VAT:

  • Combi to combi boiler swap – £1,529
  • System/Standard boiler to combi conversion – £2,249
  • Back boiler to combi conversion – £2,499
  • System to system – £1,995 (Free Hive Smart Thermostat Inc.)
  • Standard to standard – £1,649 (Free Hive Smart Thermostat Inc.)

Moving boiler costs

You can expect to pay £300-800 to get your boiler relocated. This depends on how far the heating engineer will move your boiler and the type of boiler you have.

Moving the boiler is a complicated process; the pipework leading to the boiler must be rerouted and reconnected, which can mean pulling up floorboards.

Costs could increase if additional parts are needed for the new location.  For example, moving the boiler from the kitchen (where the flue is horizontal) to the attic (where the flue will have to run vertically) will increase the cost.

Generally speaking, the further you move your boiler from its current location, the higher the cost due to the labour of running the new pipework and the cost of the materials needed.

If your new boiler location is in the same room or reasonably close to the old one, moving your boiler should take half a day (or a day max).

And if you’re moving a boiler from the kitchen to the loft, expect it to take a minimum of one day or probably two days.

Here at WarmZilla, we charge £150 to move your boiler within the same room, £300 for other rooms, and £500 to move your boiler into the loft.

New boiler costs

Many factors contribute to the price you’ll pay to get a new boiler, including;

  • The boiler size you’ll need
  • The boiler brand you’d like
  • The boiler type
  • And the cost of replacing your boiler

To know how much a new boiler will cost, fill out the WarmZilla online survey. You’ll get a free quote in seconds.

What you need to know when buying a boiler replacement

Finding the right boiler could be a minefield. You might ask yourself, “do I need a 32kW boiler?” or “maybe I should get an Ideal boiler because it sounds… ideal?”. 

We’re here to help! After reading the next part, you ideal-ly know the right boiler for your home.

1. Boiler Size

The size of the boiler is measured in kilowatts (kW). A kilowatt is a unit that defines how much energy your boiler outputs in the form of heat.

As a general rule, the size of the boiler indicates how powerful it can be. Choosing the right size kW boiler will ensure that your home is warm enough and you always have enough hot water when you need it. To find out what size kW boiler you need to heat your home, take a look at our guide.

Here are our guidelines on the boiler size you’ll need for your home;

Combi Boiler kW Size Guide

No of bedrooms and bathrooms

Poorly insulated property

Moderately insulated property

Well insulated property

1 bed + 1 bath


2 bed + 1 bath




2 bed + 2 bath

3 bed + 1 bath28kW26kW24kW
3 bed + 2 bath28kW28kW24kW
4 bed + 1 bath30kW30kW28kW
4 bed + 2 bath32kW32kW30kW
5 bed + 2 bath40kW35kW30kW

System Boiler kW Size Guide

No of bedrooms and bathrooms

Poorly insulated property

Moderately insulated property

Well insulated property

1 bed8kW7kW5kW
2 bed8kW7kW6kW

3 bed

4 bed12kW10kW7kW
5 bed15kW12kW9kW
6+ bed18kW15kW12kW

Regular Boiler kW Size Guide

No of bedrooms and bathrooms

Poorly insulated property

Moderately insulated propertyWell insulated property
1 bed7kW6kW4kW
2 bed8kW7kW5kW
3 bed9kW8kW6kW
4 bed10kW9kW7kW
5 bed14kW10kW9kW
6+ bed16kW14kW10kW

With better home insulation and more efficient boilers, there’s no need to oversize your boiler unless you are considering; 

  • an extension
  • converting a room into an en-suite
  • adding another shower
  • adding additional radiators into your home
  • or anything else that could increase your boiler’s hot water or heating demand.

 In a nutshell, there is no need to oversize your boiler anymore; you would just be wasting energy – it’s terrible for your bank account and the environment!

2. Boiler Type

The first step of the journey is to know the type of boiler you’ve got. Put simply, there are three types of boilers on the market; combi, system, and conventional boilers. Here’s a quick breakdown to help you understand these three boiler types; 

  • Combi boiler, short for combination boiler, is a type of boiler that provides both heat and hot water without the need for a separate water tank or cylinder. It works by heating water on demand, as it flows through the boiler, rather than heating and storing a large amount of water in a tank.
    When a hot water tap is turned on, cold water enters the boiler and is heated by a gas burner or electric element. The heated water then travels through the pipes to the tap, providing hot water. When the heating is turned on, the same process occurs, but the heated water is sent to the radiators to provide heat to the home.
    Combi boilers are efficient because they only heat the water that is needed, rather than keeping a large tank of water constantly hot. They also save space because they don’t require a separate tank or cylinder. However, they may not be suitable for larger households with a high demand for hot water, as they may struggle to keep up with demand.
  • System boiler, also known as a sealed system boiler, is a type of boiler that heats water directly from the mains and then pumps it to the radiators and hot water cylinder. It uses a stored hot water cylinder to supply hot water to the central heating and hot water systems, rather than heating water on demand as a combi does. This means that it doesn’t need a cold water storage tank or hot water cylinder in the loft, making it a more compact and space-saving option. A system boiler typically includes a built-in expansion tank and pump, which helps to maintain the proper pressure and flow of water throughout the system.
  • Conventional boilers (known as regular boilers) have a hot water tank and a cold water storage tank (usually in the attic). Conventional boilers are useful for homes with low water pressure as they utilise a ‘gravity-fed’ system but due to the tanks involved, most homes switch to a combi boiler when replacing a regular boiler.

After you’ve figured out the type of boiler you currently have, you need to think about the type of boiler you’ll want to replace it with. 

Generally speaking, it’s usually easier to swap boilers if they’re the same type, for example, swapping out a combi boiler for another combi boiler. Sometimes, this might not be doable, so your boiler will take longer to fit.

Check out our blog to learn about boiler swaps and how much they cost.

3. Energy Efficiency Rating

Choosing a highly-rated, energy-efficient boiler is a great way to lower your heating bills and ensure you’re doing your bit for the environment. If you want to maximise your boiler’s energy efficiency, read our blog here.

The efficiency of your boiler can depend on a number of factors such as whether your boiler is a condensing or non-condensing unit, the age of your boiler, whether your boiler’s kW size is compatible with your homes needs and demands, and how many people are using the heating system at one time, etc.

When buying a replacement, always look for the highest energy efficiency boiler you can find because that will save you money on your heating bills. Check out our most energy-efficient boilers in 2023.

The top 5 replacement boiler brands

1. Worcester Bosch Boilers

Worcester Bosch is by far the best boiler brand out there. It is the Rolls-Royce of boilers!

YouGov ranked Worcester Bosch in the top 3 as one of the most popular home appliance brands (Q1 2022).

It’s no surprise that Worcester Bosch came first according to Which? Best Boiler Brand survey 2022.

Here’s why they are the best;

2. Viessmann Boilers

Viessmann offers a full range of high-quality products representing German engineering at its finest.

They manufacture highly reliable boilers with outstanding performance, which is one reason Viessmann constantly picks up the Which? Best Buy award.

Why choose Viessmann? 

  • Stainless steel heat exchanger* 
  • 10 years guarantee (with WarmZilla)
  • Great customer reviews (rated 4.4 on Trustpilot)
  • Energy-efficient boilers
  • Easy to service and repair
  • Known for its great aftercare

*The benefits of a Stainless steel heat exchanger

There are many benefits of using stainless steel for the heat exchanger. First, stainless steel offers impressive resistance against corrosion, meaning your heat exchanger is more likely to last for longer and maintain its efficiency, saving you money on your heating bills.

Second, stainless steel heat exchangers can withstand a higher flow rate than exchangers made from other materials. If more gas or water can pass through faster, your water can be heated up more quickly. This increased flow rate also minimises the risk of blockages within the exchanger from debris or rust, and this could again increase its lifespan.

Finally, stainless steel is self-cleaning and a very lightweight material, making it ideal for various appliances that require water to be heated.

All Viessmann’s condensing boilers have stainless steel heat exchangers, so you can be assured that your boiler will run at maximum efficiency.

3. Vaillant boilers

Vaillant is another great German-owned brand. Although Vaillant offers German engineering and design, all its boilers are made in the UK.

The Vaillant boiler range has been given a Which? Best Buy award has also been awarded a Quiet Mark Accreditation from the Noise Abatement Society.

Why choose Vaillant?

  • 10 years guarantee (with WarmZilla)
  • Great customer reviews (rated 4.6 on Trustpilot)
  • Parts are relatively easy to find
  • Energy-efficient boilers
  • Easy to service and repair
  • Brilliant aftercare

4. Baxi boilers

Baxi Heating have been manufacturing boilers in the UK since 1866. According to Which?, “Baxi is one of only three brands to earn five stars for ease of servicing”. Their boilers are known for their reliability and durability. They offer great customer service.

Why choose Baxi?

  • 7-years guarantee
  • Good customer reviews (rated 4.5 on Trustpilot)
  • Made in the UK – Parts are relatively easy to find
  • Energy-efficient boilers
  • Easy to service and repair
  • Great aftercare

Note – unfortunately, WarmZilla does not currently sell Baxi boilers.

5. Ideal boilers

Ideal boilers were founded in 1905, giving them over 100 years of experience in delivering boilers to homes throughout the UK.

Ideal offers budget-priced boilers at mid-range quality, with exceptional customer service. WarmZilla is proud to offer Ideal boilers as they meet the WarmZilla standards for reliability, price, and aftercare.

Why do we recommend ideal boilers?

  • Affordable boilers – pricepoint suitable for landlords and those on a budget 
  • 10 years guarantee (with WarmZilla)
  • Fantastic customer reviews (rated 4.8 on Trustpilot)
  • Parts are relatively easy to find
  • Energy-efficient boilers
  • Easy to service and repair
  • Excellent aftercare

To sum up, here is a side-by-side comparison of the top 5 replacement boiler brands

BrandOverall ScoreReliability ScoreBrand Customer ScoreBrand Engineer Overall ScorePrice for a 30kW Combi
Worcester Bosch84%5 stars  5 stars  4 stars £800-£2,460
Viessmann81% 5 stars  5 stars  4 stars £780-£1,280
Vaillant76% 4 stars  4 stars  5 stars £1,160-£1,410
BAXI76% 5 stars  4 stars  4 stars £880-£1,000
 Ideal74% 5 stars  4 stars  4 stars £590-£1,270

Here at WarmZilla, our mission is to give you all the help and support you’ll need to find the best boiler for your home at the best price, that’s why we’ve written blogs about the best combi boilersbest system boilers and best conventional boilers in 2023. So make sure to check them out!


You can expect condensing boilers to last around 15 years or even longer if it was well maintained.

Look at the boiler type, size, flow rate, boiler price, installation costs, efficiency rating, reputation, longevity, warranty and aftercare. 

All WarmZilla boiler prices include Gas-Safe installation as standard. Each price also includes a system filter, system cleanse, guarantee, smart thermostat, and any other bits and bobs you need to get your boiler up and running. 

The best boiler brands are; Worcester Bosch, Viessmann, Vaillant, Baxi & Ideal.

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