Heatable uses cookies to give users the best possible experience.

View Policy

Black Friday Boilers
We've knocked £100 off, everything.

COVID-19 Notice
We're still installing boilers, safely. Read more.

Best Boiler for a 3 Bedroom House: Sizes & Costs

Most expensive doesn't always mean most performance. Here, we'll dive in to the biggest factors you should consider when buying a new boiler for your 3 bedroom house. Enjoy.

Do you live in a 3 bedroom house and are curious to know which boiler is the right choice? 

For most people a modern combi boiler will be the best option, hence why it’s the most popular type of boiler in the UK. 

However, depending on your home’s hot water demands a heat only or system boiler may be more appropriate. 

So, let’s uncover which is the best boiler for your 3 bedroom house….

Is a combi boiler the best choice for your 3 bedroom home?

Is a Combi Best 3 Bedroom House

A combi boiler or combination boiler provides both heating and hot water on demand from a single wall-mounted unit. They take their water directly from the mains water supply and modern A-rated models are extremely efficient. 

For the majority of 3 bedroom homes, a combi boiler will perform amazingly well at meeting your home's heating and hot water requirements. 

Worcester Combi BoilerThe average 3 bedroom home will require around 4-10 kW per day depending on how well the property is insulated. Combi boilers are offered in a range of sizes or power outputs ranging from 24 kW to 54 kW, however, this is for hot water. For heating, combi boilers offer much lower heat outputs of around 18 kW. 

This means that if you have multiple bathrooms in your home that are likely to be used simultaneously, a combi boiler may struggle to maintain a good supply of hot water to both outlets. 

In addition, if you have more than 3 bedrooms and therefore more radiators than average, a combi boiler may struggle to maintain adequate heating. 

Does your home have a high hot water demand (multiple bathrooms)? You may want to dodge a combi.

There are other situations where a combi boiler may not be appropriate, but these are less common. They include low mains water pressure, as well as incompatible pipework. 

In any of these scenarios, either a system or regular (heat only) boiler would be more appropriate. 


Sizing a combi boiler for your 3 bedroom home 

What Size Combi 3 Bedroom House

To determine what size boiler you require for your home i.e. what power output (in kW), you can use this formula for an estimation: 

  • 1 kW for small radiators or towel radiators 
  • 1. 5 kW for an average sized radiator 
  • 2 kW for a large radiator 

Using the above scores and the number of radiators in your home, add them all together to determine the total kW required. 

You can read our full guide on “what size boiler do I need?” for more in-depth guidance and information, or use our quick tool to determine the exact boiler that’s best for your home. 

Best combi boilers for your 3 bedroom home

Best Combi 3 Bedroom House

To determine which are the best boilers available in 2021, we considered the following factors: 

  • Warranty period offered by the brand 
  • The overall reputation of the brand based on customer reviews 
  • TrustPilot reviews  
  • Awards and accolades e.g. Which? Best Buy Awards
  • Customer service performance 
  • The price range of their boilers  
  • Efficiency ratings

The cost of a boiler doesn’t always necessarily mean it’s better either, so we have included some brands that are considered “budget-friendly”, yet are still technically brilliant. 

You can read our comprehensive guide in which we rank the best boiler manufacturer’s here

Best combi boilers for smaller homes:

Best condensing boilers for larger homes:

Best offensively large, powerful combi boilers:

  • #1 - Worcester CDi Highflow 44kW / 55kW
  • #2 - Viessmann 111-W 35kW

Is a system or regular boiler better for your 3 bedroom home?

System or Regular Better 3 Bedroom House

As mentioned, if your home has a high hot water demand, a combi boiler may not be able to keep up with the demands, in which case a regular (heat only) or system boiler will be more appropriate. 

System and regular boilers both have someting in common, a separate hot water cylinder.

The boiler supplies hot water to the central heating, while the storage cylinder provides the hot water. 


The storage cylinder is where the hot water is kept before use, since it offers a considerable reserve of hot water, it is more appropriate for situations where two or more water outlets may be being used at the same time. 

Immersion/Hot Water Cylinders

They also have the backup of an immersion heater, which is great.

Sizing a system or regular (heat-only) boiler

Size System or Regular Boiler

The average 3 bedroom property will require between 4-10 kW a day depending on the age of the property and level of insulation.

System and storage boilers are offered in a range of different sizes (power outputs) starting at 11 kW, which is sufficient for most homes of this size. 

The size of the hot water storage cylinder is another important consideration. Most storage cylinders are heated via an internal metallic coil. The coil itself has its own power capacity measured in kW that it requires from the boiler to heat the water in a reasonable length of time, which is referred to as the hot water recovery time.

So similar to a combi boiler, to determine the size boiler you require, use the following formula: 

  • 1 kW for small radiators or towel radiators 
  • 1. 5 kW for an average sized radiator 
  • 2 kW for a large radiator 

Using the above scores and the number of radiators in your home, add them all together to determine the total kW required. Then add 3 kW to account for your hot water storage cylinder. 

The Viessmann 111 - The Hybrid Solution

Viessmann 111

The Viessmann Vitodens 111-W is one of the brands most notable innovations - a storage combi hybrid that is able to meet the high hot water demands of any modern family home, without the need for a separate hot water storage cylinder. 

Viessmann Boilers

The boiler is relatively large and is certainly larger than the average size combi boiler, but if you do want to save space and avoid the need to house a separate cylinder it still offers an advantage. 

Internally, the Viessmann 111 includes a combi boiler on one side, offering 35 kW of central heating power, and a hot water boiler on the other, offering 35 kW of hot water performance. 

Viessmann 111So if you are looking for a boiler that can meet your home's high demand for hot water, but don’t have the room to house a separate storage cylinder, the vitodens 111-W may just be the best boiler for you and your family. 

It offers you the ability to run between two to three showers at once, up to a maximum of 18 litres per minute. 

What happens if you choose the wrong size boiler? 

If you underspec your boiler....

In the case of combi boilers, selecting a combi boiler that is too small i.e. has a lower heat output than your home requires is not typically an issue. 


The majority of combi boilers are designed to heat up to around 14 to 20 radiators. 

The issue is typically going to arise from the boiler not being able to meet your hot water demands, therefore, it’s important to ensure the combi boiler heat output matches your cold water flow rate. 


If you overspec your boiler...

If you choose a boiler that is too large for your home i.e. the heat output, then this generally isn’t an issue. 


Newer boilers have something referred to as modulation. In basic terms, this means that the boiler reads some sensors and is able to adapt e.g. by reducing the heat output if it senses a lower demand. 

Looking for the best deal on a new boiler? 

Heatable New Boilers

If so, choose Heatable, here’s why: 

  • Gas Safe installation within 24 hours
  • Thousands of happy customers – an average score of 4.6 on Trustpilot (that’s better than the market leader)
  • Price match guarantee – if you find a cheaper quote, we will match (must be like for like)
  • Multiple payment options - interest free available
  • 10 year guarantee
  • Fixed price guarantee – no hidden costs
  • Save your quote until later

Use this clickable form to get a fixed price on the screen instantly.

More advice

New boiler deals

Buy your new boiler, better

Get a fixed price on a Which? Best Buy in minutes

Heatable is registered in England and Wales No. 08804726 (VAT No. GB205805920 ). Trading address is 1 Station Road, Great Sankey, Warrington, Cheshire, WA5 1RH. Heatable acts as a credit broker (not as a lender) and offers credit products through a panel of lenders. Heatable is authorised and regulated by the Financial Conduct Authority (reference no. 805259).

[1] Price based on a like for like combi swap in a 2 bed, 1 bathroom terraced home with a standard flue

[*] Installation dates are subject to installer availability

[ยน] only available on combi boiler installations

Financial Support: If you are in receipt of certain benefits, you may be entitled to claim a free boiler grant.