Boiler Installation Guide

Need a new boiler?

In this guide, we'll explore everything you need to know about new boiler installation costs, what's involved in fitting a boiler, how long it takes, and whether it's DIY-friendly.

We'll also discuss how a boiler is maintained, and what you should consider when hiring a boiler specialist.

Let's get into it.

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What Is Boiler Installation?

Boiler installation involves connecting a boiler to your home's central heating and hot water system.

A boiler provides heat for your home's radiators and supplies hot water for taps and showers.

Depending on the type of boiler, it may be connected to your home's hot or cold water storage tanks.

Types of Boiler

There are several types of boiler found in UK homes. Let's take a closer look:

Combi Boiler

A combi, or combination boiler, makes use of a single compact central heating boiler unit and water heater.

Since combi boilers heat the water straight from the mains, a water storage tank is not required.

Pros

• ✔ Relatively inexpensive to install.
• ✔ Highly efficient, and heats up water quickly.

Cons

• ✖ Not compatible with power showers or immersion heaters.
• ✖ Pressure can be limited if multiple taps are used at the same time.

System Boiler

A system boiler heats water for your home's central heating and hot water cylinder.

There's no need for a separate cold water tank, just the boiler itself and a hot water cylinder.

Pros

• ✔ No cold water tank required.
• ✔ Easy to install compared to heat-only boilers.

Cons

• ✖ Needs more room than a combi boiler.
• ✖ Hot water isn't instant.

Heat-Only Boiler

A regular, heat-only boiler, also known as a conventional boiler, needs a hot water cylinder and a cold water tank.

With a heat-only boiler, it's possible to get hot water regardless of the water's pressure in the mains. You can have hot water for multiple sources simultaneously with this type of boiler, too, making it suitable for large households.

Pros

• ✔ Provides hot water, even with low mains pressure.
• ✔ Suitable for large households.

Cons

• ✖ Lots of space needed for a tank and cylinder, as well as the boiler.
• ✖ Can be less efficient than other boilers.

Electric Boiler

An electric boiler uses electricity instead of gas or oil to run.

Electric boilers are typically small and compact, quiet in operation, and easy to maintain, but their running costs are typically higher than gas.

Pros

• ✔ Easy to install.
• ✔ Compact, no external flue required.

Cons

• ✖ Running costs are higher than gas.
• ✖ Not cost-efficient for large households.

Oil Boiler

Oil boilers require an external tank, filled with oil, which is burned to provide hot water and central heating.

If you can't access a gas connection or live in a rural, off-grid location, oil boilers can provide a good heating alternative.

Pros

• ✔ Useful heating solution for off-grid homes.
• ✔ Good efficiency for large households.

Cons

• ✖ Needs an external storage tank.
• ✖ Higher running costs than gas.

Biomass Boiler

Biomass boilers work by burning wood pellets, logs, or chips.

They're a renewable heating option, and are useful for off-grid homes.

Pros

• ✔ Renewable energy.
• ✔ Reduces reliance on fossil fuels.

Cons

• ✖ Much higher installation cost compared to other boiler types.
• ✖ Requires fuel storage.

How to Tell if You Need a New Boiler

A few signs can suggest it's time to think about a replacement rather than another repair:

• Age — A boiler that's serviced every year will usually last 10 to 15 years, so one nearing the end of that range is more likely to need replacing than repairing.
• Frequent Breakdowns — If you're calling an engineer out several times a year, or repair costs are adding up, a new boiler could work out cheaper in the long run.
• Poor Heating Performance — Radiators that take longer to warm up, or rooms that never quite reach temperature, can point to a boiler that's struggling to keep up.
• Pilot Light or Error Code Issues — If the pilot light keeps going out or the boiler repeatedly displays fault codes, this may signify a fault that isn't worth repairing on an older model.

If any of these sound familiar, it's worth getting a heating engineer to assess whether a repair or a full replacement makes more sense.

Why Should I Install a New Boiler?

Improved Efficiency

One of the advantages of fitting a new boiler is that it will offer significantly improved efficiency over what you're currently getting, especially if you have an old boiler.

As a general rule of thumb, the newer the model, the better the result.

Technical Upgrades

Many modern boilers allow multi-zone heating, advanced scheduling, and compatibility with smart home integrations, giving you better control over your home's heating.

Changing Boiler Type

You may wish to change boiler type to improve efficiency, save on money, or lower your carbon footprint.

How Much Does It Cost to Install a Boiler?

The average cost to install a new boiler is around £2,400.

Depending on the type of boiler and the complexity of the installation, this figure can change. See our boiler installation cost guide for a full breakdown by boiler type.

Who Can Install a Boiler?

Boiler installation is not a DIY job.

Depending on your boiler's fuel type, you'll need different contractors to install it. The below rules apply in England, so those elsewhere in the UK should check laws locally. The only exception is Gas Safe, which applies across the whole UK.

• Gas Boilers — Only Gas Safe registered engineers can legally install gas boilers in the UK.
• Electric Boilers — The legal requirement is that the work meets Building Regulations Approved Document P, which you can satisfy by hiring an installer registered with a competent person scheme (such as BESCA, Certsure, or NAPIT) or by having building control inspect the work.
• Oil Boilers — As above, the installation must meet Building Regulations. You can do this by hiring an engineer registered with a competent person scheme that covers oil (such as OFTEC, APHC, or NAPIT) to self-certify the work, or by having the job notified to building control.
• Biomass Boilers — Biomass installations must also meet Building Regulations. HETAS is the main competent person scheme for solid fuel appliances, although other approved schemes may also cover this type of work. If the installer cannot self-certify, building control will need to approve the installation.

How Long Does It Take to Install a New Boiler?

A boiler installation typically takes 1 day.

If you're having a new fuel type installed, this timeline will be increased and will depend on factors like ease of access, coordination between energy suppliers, and the complexity of the installation itself.

Do You Need New Radiators or Pipework?

In most cases, you can keep your existing radiators when you install a new boiler, whatever type you choose, even an electric one. It's the heat source that changes, not the radiators themselves.

What often does change is how the system is protected and controlled. A new boiler installation will usually include cleaning or flushing the system, adding a magnetic filter, fitting thermostatic radiator valves (TRVs), and balancing the radiators. Under the Building Regulations, the system must be cleaned and treated with an inhibitor when a boiler is replaced, and each heated room should have suitable thermostatic controls.

Pipework is usually reused too, if you're swapping like-for-like. It's more likely to need changing if you're converting between boiler types, as this can mean removing a cylinder and tanks and re-routing the pipework to suit.

Building Regulations and Planning Permission for Boiler Installation

New boiler installations need to meet building regulations in the UK.

In England, building regulations approval is usually free, since an installer registered with a competent person scheme can self-certify the work rather than pay for a separate application. If an unregistered installer carries out the work, it needs to be notified to building control instead, which typically costs £370 to £400.

Planning permission is usually not required for boiler installations, as long as:

• Flues on the side or rear elevation of a property are not more than 1 metre higher than the tallest section of the roof.
• In a conservation area, an Area of Outstanding Natural Beauty (AONB), or another designated area, the flue isn't fitted on the front of the house or on a side wall that faces a road.

Listed homes are treated differently, so check with your local council before a new flue is fitted. You'll usually need listed building consent, which is separate from planning permission and has no application fee.

If planning permission is required, the current rate is £548 in England. Those based in other parts of the UK should check local laws and fees.

How to Maintain a Boiler

Here are some ways to keep your boiler healthy over the years:

• Book an annual boiler service.
• Run the heating regularly.
• Bleed your radiators once a year.
• Keep an eye on your boiler pressure, and top it up if needed.
• Protect the condensation pipe from freezing in extreme temperatures.
• Ensure a carbon monoxide alarm is fitted near your boiler.
• Hire professionals if you have any concerns.

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Questions to Ask When Hiring a Heating Engineer

Before you settle on a heating engineer to hire, make sure you bear the following in mind:

• Make sure your contractor is qualified/certified for your boiler's fuel type (e.g., gas boilers need Gas Safe registered engineers).
• Find out if the contractor has public liability insurance.
• Ask if there are any guarantees or warranties on the labour and parts.
• Check if waste disposal (e.g., of the old boiler) is included, or charged as an extra.

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