Combi boiler controls

Combi boilers are more energy efficient than older types of boilers, but how much do they cost? (Image credit: Adobe)

Combi boilers, also known as combination boilers, are the most popular type of boiler across the UK because of their smaller size and being more economical than regular alternatives. These boilers provide both central heating and hot water from the same compact unit.

Combi boilers supply hot water directly to your taps or radiators without the need for a separate hot water cylinder or cold water storage tank in your loft. These boilers are popular because they are economical, highly energy efficient and cost-effective. This is because they only supply hot water on demand; therefore, you only pay for what you use. 

The compact size of these boilers make them ideal for smaller properties. In addition, homeowners don’t need a lot of pipework to get the boiler working, which reduces the installation costs.

What types of combi boilers are there?

Boiler companies make combi boilers that are compatible with different fuel types. For instance, Worcester Bosch has a number of combination boilers in its range that are compatible with gas, oil and LPG fuel. We can differentiate the combi boilers based on whether they use gas, oil, LPG (Liquified Petroleum Gas) or electric.

Gas combi boiler

These combi boilers run on natural gas that is supplied to homes via the national gas grid network. It’s the most commonly used boiler fuel in the UK because most homes are connected to the grid; therefore, it’s easy to fuel. While it’s known to be damaging to the environment, it’s a cleaner and cheaper fossil fuel than oil and coal. 

LPG combi boiler

Liquefied Petroleum Gas (LPG) is a combined product of natural gas and oil extractions. More manufacturers are producing LPG compatible combi boilers because they are slightly cleaner than oil. It’s a good alternative if you are unable to access the gas grid. 

Oil combi boiler

If you are not connected to the gas grid, you can also use the oil combi boiler. The oil supply must be stored in an external tank on your property; therefore, you need to have additional space for this. You can sink the tank into the ground to save on space. Additionally, you’ll need to order refills before the tank is empty; otherwise, you won’t have hot water or heating in your home if the oil runs out. 

Electric combi boiler

Electric powered combi boilers are highly energy efficient. Water is heated without any waste because all the energy is transferred from fuel to heat. However, this could be expensive because you need to pay electricity bills to keep the boiler up and running, and electricity is typically more expensive than gas or oil.

How much does a combi boiler cost?

Installing a new A-rated combi boiler has a varied price range and there are many things that affect the cost. Things like the size of your new combi boiler will greatly affect the cost. Different brands also carry different price ranges too, so this is something to consider when you’re choosing which combi boiler is right for you.

Based on our research and using the costs from our reviewed brands, the below table is the average cost you can expect to pay for a combi boiler in the UK.


Boiler typeAverage combi boiler costCombi boiler installation priceAverage cost of combi boiler including sundries and installation
Combi boiler£848 – £1,800£300 – £1,000£1,648 – £3,000

What affects the cost of a new combi boiler?

As well as the average cost of installing a combi boiler which can cost between £1,648 and £3,000, you should also consider the additional parts. According to Energy Saving Trust, adding other parts could cost up to £4,000.

Thing’s to consider when choosing your new combi boiler:

  • Fuel type
  • Add ons
  • Boiler size
  • Brand and model

Fuel type

As already mentioned, combi boilers can be compatible with gas, LPG, oil or electric. Homeowners will choose their preferred fuel source depending on the infrastructure in their neighbourhood. If you live near the national gas grid, it would be cheaper to use gas-compatible combi boilers.

Oil combi boilers could be a bit more costly because you need an additional tank to hold the oil. Additionally, oil prices fluctuate regularly, which can affect your spending. On the other hand, electric combi boilers use electricity; therefore, they are more energy efficient. However, they can increase your monthly electricity bill and may not be powerful enough for larger homes

Added features & replacements

You could incur more costs if you need to add features or replace an old boiler. These costs could include adding electrical wires, installing new pipes, modifying the power source or purchasing additional tanks. This happens mostly when you need to switch from one fuel source to another. 

For instance, if you are moving from oil to gas, you need to install new pipes and dig out old oil tanks. In addition, replacing a regular or system boiler with a combi boiler may be more costly depending on whether the pipework in your home needs to be changed. 

Boiler size

If you live in a large home with several bathrooms, you might need a more powerful boiler. The larger the boiler, the higher the cost. In addition, larger heaters need more infrastructure to install and additional labour, which can increase the upfront costs. To get the correct boiler size for your home, you can consult a certified boiler installer for recommendations.

Brand and model

There are different brands in the UK dealing in combi boilers, including Vaillant, Ideal Heating, Worcester Bosch and Viessmann. Every boiler brand has a different price point. While some models are cheaper, others might be out of your budget. When choosing a brand, ensure that it’s reliable, affordable and ideal for your home. 

Here’s the price comparison of different combi boilers.

Brand and modelAverage Cost
Worcester Bosch Greenstar 4000£1,200–£2,500 (excluding installation)
Viesmann Vitodens 111-W£1,575–£3,000 (excluding installation)
Vaillant ​​ecoTEC Green iQ 835From £1,525 (excluding installation)
Baxi Platinum Combi£850–£1,250 (excluding installation)
Ideal Logic+ 24kWFrom £848–£1,011 (excluding installation)

What is the cost of replacing an old boiler with a combi boiler?

What does a combi boiler cost

Replacing an older boiler with a combi boiler could cost more if your house needs new pipework. (Image credit: FMB)

If you already have a boiler in your home that you need to switch, you can replace it with a combi boiler, which can be much cheaper to run. For instance, if you are replacing a regular boiler with a combi one, this could cost you from £2,500 to £4,000. The initial costs are higher because you need to pay for the new boiler itself, installation costs and removal of the older boiler.

In addition, your installer might need to change the pipework or location of your boiler, which can be costly and time-consuming. You should replace your boiler if the efficiency has deteriorated, to boost longevity, improve reliability and potentially add to the value of your property. Before replacing an old boiler, ensure that you budget for any extra costs.

What are the advantages of combi boilers?

Highly efficient: Modern combi boilers are highly energy-efficient. For instance, Vaillant produces an ErP A rated combi boiler with up to 94% efficiency, which reduces fuel bills and saves money. 

Small size: A combi boiler is compact and doesn’t require extra water tanks, so it’s small enough to be stored inside a cupboard in your kitchen. This also makes installation very quick and easy, potentially reducing the cost and time spent during installation.

Hot water on demand: The combi boiler takes its water supply directly from the mains; therefore, your hot water is delivered whenever you need it.

What are the disadvantages of combi boilers?

Not always compatible with old pipework: If you plan to upgrade the heating system in an older house, the existing pipework might not be compatible with the new, more powerful boiler. Therefore, you have to replace the pipes, which will add to the overall cost of the installation.

How much can you save with a new combi boiler?

Installing a new combi boiler could save you hundreds of pounds on your energy bills per year. The exact amount that you’ll save will depend on your house and boiler size.

According to Energy Saving Trust, this is how much you can save if you replace your old gas boiler with a new A-rated combi boiler based on October’s energy prices.

Energy rating
Property typeD (78-82%)E (74-78%)F (70-74%)G (<70%)
Detached house£375£460£590£840
Semi-detached house£305£335£380£540
Mid-terrace house£235£260£290£420

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