April 01, 2021

Which Boiler is Best for a 4 Bedroom Home?

When your old boiler breaks down and it comes time to replace it with a new one, it might seem difficult to choose which boiler is best for your home, especially now there is such a wide range of boilers available on the market.

Which Boiler is Best for a 4 Bedroom Home?

Selecting the wrong boiler for your home could lead to issues such as inadequate heating, failure to meet the demand for hot water and high energy bills. In this guide, we’re going to be looking at which boilers are best for a four bedroom home. If you're more interested in which boilers are most suited for a 3 bedroom home, take a look at our alternative guide.

To make sure you get the right boiler for your home, there are a few things you should consider before buying. This includes the:

  • Type of boiler
  • Output size
  • Physical size
  • Efficiency
  • Warranty available

Type of Boiler and Boiler Size

When discussing boiler size, we are often referring to the output in kilowatts (kW) as opposed to the physical dimensions of the boiler itself. Kilowatts are the measurement of energy that is output by the boiler in the form of heat. The correct size of boiler for your home depends on your demand for hot water and the number of bedrooms, bathrooms and radiators you have. The general rule of thumb is the higher your demand for heat and hot water, the higher the output you’ll require.

The kW outputs are measured differently for each type of boiler, so you should choose the appropriate kW for the type you will be buying.

Combi Boilers

A combination or ‘combi’ boiler is a gas boiler that combines a water heating system and a central heating unit into a single body to produce hot water instantly, so there is no need for a separate hot water tank. An advantage of combining two different boilers into one body is that they take up much less room in your home compared to system or regular boilers, making them ideal for homes where space and storage is an issue.

Output in kW Bedrooms Bathrooms Radiators
24-28 1-2 1 Up to 10
28-35 3-4 1-2 Up to 15
35-43 4+ 2+ Up to 20

As your home has four bedrooms, you would require a combi boiler with an output between 35-43kW. If you live in a medium sized home with up to 15 radiators, you would most likely need a 35kW boiler, whereas if you live in a large house with up to 20 radiators, you’ll need a 43kW boiler.

System Boilers

System boilers heat your central heating system and produce hot water for a water storage cylinder, directly taking the water from the mains as opposed to using a feed and expansion tank like a regular boiler.

Output in kW Bedrooms Bathrooms Radiators
12-15 1-2 1 10
18-24 3-4 1-2 15
30+ 4+ 2+ 20

As your home has four bedrooms, you’ll need a boiler with an output between 24kW and 30kW+. If you have 1-2 bathrooms, you’ll likely just need a 24kW system boiler, whereas a home with 2+ bathrooms will likely need a 30kW boiler.

Regular Boilers

Regular boilers are also known as ‘conventional’ or ‘heat only’ boilers because they don’t provide domestic hot water on demand the same way combi boilers do. Instead they store hot water in a cylinder until it needs to be delivered to a tap or shower. An advantage of this is that they can meet a high demand for hot water at once, making them ideal for properties with multiple bathrooms, though when the water does run out, you'll have to wait for it to fill up again.

Output in kW Bedrooms Bathrooms Radiators
10-18 1-2 1 10
18-26 2-3 2-3 15
27-40 4+ 3+ 20
Cylinder Capacity (Litres) Bedrooms Bathrooms
120-150 1 1
180 2 1
210 3 2
250-300 4 2
300+ 4+ 2+

As your home has four bedrooms, you’ll need a boiler with an output between 27kW-40kW and a cylinder with a 250-300 litre capacity. If you have 2-3 bathrooms, you’ll likely just need a 27kW system boiler, whereas a home with 3+ bathrooms will likely need a 40kW boiler.

There are some exceptions when it comes to choosing the right kW, such as if you have a very large family which has a high demand for hot water or lots of radiators (20+) and lots of bathrooms, in which case you’ll need a bigger boiler output to accommodate your additional heat and hot water needs.

A lack of cavity wall insulation, loft insulation, double/triple glazed windows and decent sealing around doors and windows could mean that you are losing a lot of heat from your home and will therefore also require a higher output if you are not intending to make those changes in the near future. For more information on choosing the right size boiler for your home, read our helpful boiler size guide.

Physical Size

If storage space is a problem in your home, finding room for a physically large sized boiler can be difficult and inconvenient. Luckily, many manufacturers offer compact sized boilers for smaller spaces, such as in a kitchen cupboard or in a small airing cupboard. The Viessmann Vitodens 050-W 35kW is an example of a high output boiler that is small in physical size.


The efficiency of your boiler plays an important part in how well your boiler operates as well as the cost of your fuel bills. The higher the efficiency of your boiler, the lower the wasted fuel and therefore the lower your fuel costs. The Energy Saving Trust estimates that you could save up to £380 a year by replacing your old inefficient boiler with a new A-rated one.

If cutting fuel costs and boiler efficiency is an important factor to you, you should make sure you purchase an A-rated efficient boiler, meaning it is 90%+ efficient. iHeat only installs A-rated boilers because we believe efficiency is incredibly important. For more information, why not read our helpful guide to the most energy efficient boilers.


Boiler insurance can be expensive and sometimes unnecessary, so long as the boiler you purchase has a good warranty period. At iHeat, all of our boilers have warranties between 7 and 10 years, during which time the warranty covers your boiler against manufacturing/material defects for both parts and labour. To claim under the warranty, you must ensure that the boiler has been maintained and inspected by a Gas Safe registered engineer on an annual basis. See our terms & conditions for more information.

Our Top Boiler Picks for Homes with 4 Bedrooms

Viessmann Vitodens 100-W 35kW

- From £2,465 (Including installation)

Efficient, compact, quiet and affordable, the Vitodens 100-W gas condensing boiler is the most popular solution available at iHeat.

Featuring innovative technology and services combined with reliability and longevity and comes ready for smart technology, helping you to optimise your heating and save on energy costs. Vitodens 100-W 35kW Combi reviewed as a Which? Best Buy 2019.

Viessmann Vitodens 050-W 35kW

- From £1,920 (|Including Installation)

With compact dimensions, low weight and quiet operation, the attractively priced Vitodens 050-W is a low-cost gas condensing boiler that will integrate effortlessly into any living space and does not compromise on quality; making it ideal for both new build homes and modernisations.

Worcester Bosch 8000 Style 35kW

- From £2,740 (Including Installation)

The latest Worcester Bosch boiler features a modern new design whilst being packed with innovative new features that help keep your home warm and your boiler working at its best.

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