What Is The Cost Of Having A Replacement Boiler?

It’s never a good time to replace a boiler. However, most will scramble to find a replacement boiler as soon as it happens.

There are approximately 23 million domestic boilers installed across the UK. Around 90% of UK homes rely on a boiler system for heating and hot water.

So, what will the cost of replacing a boiler in 2025 be? The answer can vary depending on several factors. A significant factor is the type of boiler you use in your home.

Types Of Replacement Boilers Fuels In 2025

As mentioned, gas is the most common fuel type in the UK market. However, there are other fuel types on the market, which include the following:

Type Of Boiler Fuels In The UK

While gas is still the leading fuel source for most of the UK’s boilers. Other primary fuel sources include:

• Electricity
• Oil

The most common fuel source for oil boilers is kerosene 28, known as “28-second oil.” Older units use gas oil, also known as “Red diesel” or “35-second oil.”

• Air Source Heat Pump (ASHP)
• Ground Source Heat Pump (GSHP)
• Biomass
• And hybrid systems

Each of these fuel types comes with its positive and negative attributes.

Currently, electricity is the most expensive boiler fuel to run. According to Ofgem, the energy price cap for gas from 1 July to 30 September 2025 is 6.33p per kWh, with a daily standing charge of 29.82p.

By comparison, electricity costs 25.73p per kWh, with a daily standing charge of 51.37p.

The UK government has stepped back from banning the new installation of oil boilers in 2026 and extended the deadline to 2035. This delay was due to policymakers deciding that homeowners needed more time to transition to alternative heating methods.

ASHP and GSHP are technically the most economical to run. However, their main downsides are the upfront cost to homeowners and the requirement for more space for equipment to extract heat from the air or ground.

As a great alternative to using an oil boiler, homeowners in England and Wales wanting to install ASHP and GSHP can apply for financial assistance from the Boiler Upgrade Scheme (BUS). Homeowners who qualify can apply for upfront capital grants of up to £7,500.

Biomass boilers are another type of boiler for which residents can apply for additional financial help from BUS up to £5,000. Biomass boilers provide heating or hot water by burning carbon-neutral fuels like wood or pellets. They also require a sizeable upfront investment.

The last fuel type of boiler is the hybrid system. It uses two fuel sources: gas and solar. When heating the water supply, the hybrid systems ensure that they use the most affordable and available heating method. During summer, the systems preheat the water using the sun, while when the weather is overcast and cloudy, it will switch to using gas.

Type Of Boilers

Many UK boilers are available in different types. There are three main types of boilers, which include:

1. Combi Boilers (Combination Boilers)

Combi boilers are the go-to choice for many British homes due to their compact design and dual functionality. They deliver hot water and central heating from a single unit, making them especially suited for flats and small to medium-sized homes.

Combi boilers are popular because they:

• They heat water and rooms on demand
• No need for a separate hot water cylinder or loft tank
• Efficient and ideal where space is limited

Downsides?

Combi boilers can struggle with simultaneous hot water use, such as running two showers simultaneously. Additional equipment, like a pump, may also be necessary in areas with low mains pressure.

2. System Boilers

System boilers are better suited for larger homes with greater hot water needs, thanks to using a separate hot water cylinder. These boilers are often used where multiple bathrooms are frequently used.

Pros for using a system boiler include:

• Consistent hot water supply to several outlets
• No need for a cold water tank in the loft
• Compatible with solar thermal systems

Things to consider:

The heated water isn’t instantaneous and can run out if demand exceeds the tank’s capacity. Additionally, the system requires extra space for the cylinder.

3. Regular (Conventional) Boilers

Conventional boilers are often found in older homes with traditional heating layouts. They use a hot water cylinder and a cold water tank, typically installed in the loft.

Advantages include:

• Handle multiple hot water outlets with ease
• Works well in areas with low water pressure
• Ideal for homes with existing conventional setups

Regular boiler limitations include:

Usually, regular boilers require more room and don’t provide hot water on demand. This is because the water must be stored and preheated in advance.

While alternative designs exist, the types above remain the most widely used.

The average cost for certain types of boilers is as follows:

As you can tell, there is a vast difference between entry-level and higher-end boilers. But what determines these factors?

Factors That Affect the Cost of a Boiler Replacement

Regarding budgeting for a replacement boiler in 2025, several factors come into play beyond just the unit price. Here’s a breakdown of what affects the overall cost:

Brand And Model

Not all boilers are created equal. Premium brands like Worcester Bosch, Vaillant, and Viessmann typically cost more upfront but offer:

• Longer warranties
• Greater efficiency
• Better reliability

While going with a budget boiler brand may reduce the initial outlay, they often come with:

• Shorter lifespans
• More frequent repairs
• Limited aftercare support

Boiler Output Size

Boiler size is measured in kilowatts (kW), which determines how much hot water it can produce. Small homes (1–2 bedrooms) usually need a boiler between 24kW and 28kW. Larger homes (4+ bedrooms) may require a unit between 35kW and 40kW.

The larger the output, the higher the price tag for the boiler and its installation.

Installation Complexity

Labour is a significant cost driver. The more complex the job, the more you’ll pay. A like-for-like swap in the exact location is the most straightforward and affordable.

Costs increase significantly if you:

• Change boiler types
• Move the boiler to a new location
• Upgrade heating system components.

Also, depending on the installation complexity, additional items may also be required, such as:

• New flue systems
• Magnetic filters
• Smart thermostats
• Hot water cylinders

These extras can add hundreds of pounds to your final bill.

Labour Rates by Region

Installation rates can vary significantly by location:

• London & South East: Higher average hourly labour costs
• North England, Wales & Scotland: More affordable rates on average

To ensure you get the best value, make sure to compare at least three quotes from Gas Safe registered installers.

Also, always ask if the quote includes disposal of the old boiler (some companies charge extra for this).

Now that we’ve gone through all the factors that can increase the cost of your replacement boiler, what are the average prices for a new system?

Average Boiler Replacement Costs (UK – 2025)

Based on data from Checkatrade, here’s what you can expect to pay for a new boiler in 2025, including unit and installation costs:

For a standard combi boiler replacement, the total cost generally falls between £2,500 and £4,000, with the average sitting close to £3,000.

However, switching to or upgrading a system or regular boiler can exceed £4,000, particularly if significant changes to pipework or controls are required.

If you need a new replacement boiler quickly in 2025, WarmZilla can help within 48 hours.

Replacement Boilers Installed Quickly

WarmZilla makes replacing your boiler quick and stress-free. Take our simple online survey, and you’ll be served the best boiler options for your home within minutes.

Once you’ve selected your preferred boiler option, we can have it installed within 48 hours and guarantee no hidden fees.

How it works:

• Fill out a quick survey about your home and heating needs
• Get instant, fixed-price quotes tailored to you
• Choose an installation date that fits your schedule.

Gas Safe registered engineers carry out all installations, and we offer flexible finance plans on top-rated boiler brands.