Back Boiler Removal and Replacement Cost Guide 2024

If your home still has a back boiler, you may be wondering if you should replace it or leave it be.

Well, we’re about to shed some light on these trusty old contraptions, and help you decide whether to replace your back boiler, how to do so safely, and which new boiler to choose as an alternative.

What Is a Back Boiler?

A back boiler is a type of boiler that’s installed behind a home’s fireplace hearth, and gets its heat from a gas fire, open fire, or an electric heating element. Much like its other boiler cousins, a this type of boiler can provide both heat and domestic hot water.

If you have central heating, can’t see a boiler, but have a fireplace, chances are that you get your heat and hot water from a back boiler.

Why a House May Have a Back Boiler

Like combi boilers today, back boilers enjoyed considerable popularity back in the 1960s. In fact, any new boiler fitted between 1960 and 1980 would’ve likely been a back boiler. But from the 1980s on, regular, system, and combi gas boilers began to take over the market.

Then, the 2005 Building Regulations sealed the fate of the trusted, but inefficient old back boiler. The new building standards required only efficient, condensing boilers to be installed.

Are Back Boilers Now Illegal?

Old, inefficient, non-condensing back boilers are now illegal to install — as all non-condensing boilers are. That said, plenty of back boilers are still in service throughout the nation.

And, believe it or not, there was even a new-ish, condensing boiler that Baxi manufactured, with an energy efficiency rating of A — the Baxi Bermuda BBU HE Boiler. If you’re lucky enough to get your hands on this model, you can legally replace your existing boiler with a new one. Sadly, the model has been discontinued, so the supply may be limited.

Are Back Boilers Dangerous?

Back boilers may be inefficient, but they’re not inherently dangerous — as long as you keep using them.

However, if your back boiler is no longer in use, but you didn’t properly remove and decommission it, then you may have an explosion hazard on your hands. That’s because redundant boilers are often left sealed with residual moisture inside their water jacket.

When the fireplace in front of the back boiler heats this water jacket, the moisture turns to steam. In some instances, this has caused explosions with subsequent property damage, injuries, and even a fatality.

So, if you’ve got a redundant back boiler behind your fireplace, but you’re not sure whether it’s been decommissioned properly, get a Gas Safe engineer to have a look before you light the fireplace.

Back Boiler vs Combi Boiler

The “back boiler vs combi boiler” debate is a simple one to settle, and boils down to this — at some point, all back boilers will have to be replaced by combis or other modern boiler types.

That’s because you can’t really get back boilers anymore. And if your old one breaks, you won’t find replacement parts. Now, given that the back boiler’s most appealing feature was its compactness, a combi is your most logical alternative.

Should You Replace a Back Boiler With a Combi?

Most back boiler models are not energy efficient. And that means you’re losing cash on your utility bills. 

Replacing an old back boiler with an up-to-date A-rated combi boiler will save you cash, as many newer A-rated boilers are over 89% efficient.

If you are having problems with your existing boiler, it’s rarely a financially viable option to fix them.

Due to the age of these units, it’s likely other parts will deteriorate within the next few years and you’ll need to remove and replace your back boiler anyway.

Now, keep in mind — unlike a back boiler, you can’t squeeze in a combi behind a fireplace without major, messy changes to your home’s structure. That said, some combis are small enough to neatly fit into a kitchen cupboard — out of sight, out of mind.

We’d always advise upgrading from a back boiler to a new combi boiler where possible. You can get a fixed price on screen using this form from Heatable.

Back Boiler Removal Costs

The costs to remove a back boiler can vary greatly depending on how much adjacent infrastructure (such as the fireplace hearth) will need to be replaced after the procedure.

Now, if you already have a central heating system installed and want your old back boiler removed, you’ll probably pay around £700-1,000. This will include getting rid of the boiler and capping pipework.

Back Boiler Replacement Costs

Back boiler replacement costs hinge on 2 factors — how complicated (and pricey) the removal is, and what system you’d like as your upgrade. Depending on your needs, you may get a new combi boiler, system boiler, or regular boiler to replace the back boiler.

Cost of Replacing a Back Boiler With a Combi

If you’re removing and swapping a back boiler for a combi boiler, expect to pay around £3000+.

That would assume a Worcester 4000 boiler was fitted, or even the slightly older Worcester 30i.

Swapping a Back Boiler For a Regular or System Boiler

The cost to replace a back boiler with a regular or system boiler is similar to a combi replacement, assuming you settle on a model of the same output. So, you can expect to pay around £3,000 to replace your back boiler with a 30kW system or regular boiler.

That said, keep in mind that fitting a system boiler will also require you to install a hot water cylinder. You can read more about hot water cylinder installation and sizing in our guide here.

Installing Your New Boiler in a New Location

Back boiler replacement cost comprises more than just the price of a new boiler.

All boilers need a flue system to vent harmful gases outdoors. Back boilers expel exhaust fumes through the chimney, whereas newer boilers use a horizontal or a vertical flue.

You’ll need to plan a new location for your boiler. And, most of the time, that’s ideal — you can tuck your new boiler away rather than leaving it out for everyone to see.

If you are looking to replace your back boiler with a combi in a small cupboard (such as in the kitchen), you’re in luck: as we mentioned above, manufacturers design boilers specifically for this purpose. Some examples include the Worcester Bosch CDI Compact range and the Ideal Logic Plus — both boiler ranges will fit in a standard kitchen cupboard.

Normally, you should expect to pay an additional £300-600 to move your boiler to a new location during installation. You can double-check the cost of installing your new boiler in different locations (airing cupboard, loft, kitchen, and so on) here.

Back Boiler Replacement Costs

There are plenty of properties that would benefit from a full heating system installation. Remember, even if the pipework is in place, it’s likely 40-50 years old if a back boiler powers it.

So, how much does back boiler replacement cost, including all the pipework?

That’s not an easy question to answer: the price will vary from property to property.

A typical 3-4 bedroom property with 8-10 radiators, all pipework, and an A-Rated combination boiler, is likely to cost around £5,000. This includes removing the back boiler and replacing it with a combi.

Now, take this number as a guideline. The difficulty of laying pipework, the size of radiators, the size of the boiler (and type) will all contribute to the total cost of a full heating system.

And, if you need to replace a back boiler with a “system” boiler, you’ll also need a cylinder and additional pipework.

Additional Costs for Regular and System Boilers

Regular and system boilers have additional components to make central heating work. These can include cylinders and hot water tanks.

If you need to remove, replace, or repair these, you’ll incur additional costs. For cylinders, we’ve created a cylinder installation cost guide.

How to Replace a Back Boiler

Without visiting a property, it’s hard to determine the right route to take for a new boiler. Some properties will need a small combi boiler (24kW), whereas others will need a large (40kW+) system boiler.

When having any part of your central heating removed and replaced, it’s important to get more than one quote.

Quickest Way to Get a New Boiler

One of the most cost-effective ways to get a back boiler replaced and upgraded for a combi is to use Heatable. Their boiler installation prices here are lower than most national companies. You can get a range of fixed price boiler quotes by filling in Heatable’s anonymous questionnaire.

Heatable have a clickable form that asks several essential details about your property. From there, you get a fixed price on your screen in less than 2 minutes.

Using a Local Installer to Remove a Back Boiler

If you use a local installer for your back boiler replacement, here are a few things you should expect from your engineer:

• Their Gas Safe credentials.
• Where the flue will be located.
• Recommended boiler, and it’s warranty.
• A fixed-price quote.
• The quote includes boiler filter installation (so your system doesn’t gunk up).

Is There a Back Boiler Removal Grant?

There is a new boiler grant that the UK government offers as part of the Energy Company Obligation initiative. This grant is available to certain households who rely on an inefficient, 10+ year-old gas boiler for heat and domestic hot water. You can click here to see if you’re eligible.

If you don’t qualify for the grant, we suggest you find a financing deal from Heatable instead.

More Questions About Back Boilers?

Thanks for reading our back-boiler replacement cost guide.

If you have any questions regarding replacing or removing back boilers, please leave a comment below. We’ll get back to you as soon as we can.