Best Combi Boiler For A 3 Bedroom House

Last updated: November 15, 2023

Wanting to know what the best boiler for a 3 bedroom house is? Here we explain how boiler sizing works and what you’ll need.

To ensure a comfortable, perfectly heated home, you need the right boiler.

Heating accounts for over half of your household energy bill, and the right boiler can make a huge difference.

With so many boilers available, choosing the right one can be difficult.

This guide will help you choose the best boiler for a three-bedroom house.

Types Of Boilers Available

You can install three main types of boilers in your home, including:

Combination (Combi Boilers)

Combi boilers provide both heating and hot water on demand from a single wall-mounted unit, hence the name combination boiler.

They’re the most common type of boiler installed in UK homes and take their water directly from the main supply.

Combination boilers use metallic heat exchangers to instantly heat hot water on demand through combustion by burning fuels like oil or gas.

Combi boilers don’t require a separate hot water storage tank like traditional boilers. Instead, the water is heated immediately from a single unit.

Learn all about the different types of boilers, including condensing boilers, LPG boilers, oil boilers, Opentherm boilers and calculating boiler size in our guide.

Conventional Boilers (Regular Boilers)

Also called heat only or regular boilers, conventional boilers are a traditional form of central heating.

A regular boiler consists of three main components, the boiler and hot and cold-water storage cylinders.

It works by feeding hot water directly to the central heating system, including radiators, and storing hot water within the hot water storage tank for on-demand use.

The boiler receives cold water from the cold-water tank, usually located in the loft or attic, to fill the boiler with the help of gravity.

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System Boilers

System boilers are typically an upgraded version of the heat only or regular boiler. They provide heating water for your radiators and hot water on demand.

System boilers have an unvented separate hot water tank.

Water is supplied to the boiler through the mains, meaning they don’t require a cold-water tank. All parts like the expansion vessel and pump are internal.

Are Combi Boilers The Best Choice For Your 3 Bedroom House?

The average three-bedroom house requires around 4-10 kW per day, depending on how well your property is insulated.

Modern, A-rated combi boiler models are incredibly efficient and will perform amazingly well at meeting home heating and hot water requirements for a three-bedroom house.

For hot water, you can get combi boilers in power outputs from 24kW to 54kW. For heating, they offer heat outputs of around 18kW.

If your home has a high-water demand with multiple bathrooms that are likely to be used simultaneously, the combi boiler may struggle to maintain an excellent hot water supply to both outlets.

Wondering how much a new boiler costs? Check out our guide on options available if you need a new boiler but can’t afford it, as well as boilers on finance and government boiler grants here.


Pros of Combi Boilers

  • You can heat your home and the water and save a wedge on heating bills.
  • You don’t have to wait for that hot shower since they instantly heat the water you need.
  • Combi boilers also feature a compact size ideal for even the smallest 3-bedroom properties.
  • You’ll not need to make space for cumbersome water cylinders or tanks since they use the mains to heat water.

Cons of Combi Boilers

  • The water flow rate is reduced when two or more outlets are used simultaneously.
  • Combi boilers only heat water from the mains, so it may not work very well if your mains water pressure is low.
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When Is A System Or Regular Boiler Better For Your 3 Bedroom House?

A regular or system boiler can be more appropriate if your home has a high hot water demand.

System and regular boilers both have a separate hot water tank, and the boiler supplies hot water to the central heating while the storage cylinder provides the hot water.

The hot water is kept in the storage cylinder before use, offering a considerable reserve of hot water.

This makes it more appropriate for situations where two or more water outlets may be used simultaneously.

Pros of Regular Boilers

  • Provide a greater flow rate and are suitable if you have greater hot water demands like multiple bathrooms.
  • They’re suitable for older heating systems that may not tolerate high pressure.
  • They’re suitable for areas with low water pressure mains supplies that struggle to provide adequate water pressure required in combi and system boilers.

Cons of Regular Boilers

  • It may not be compatible with newer heating systems
  • You’ll need extra room for the cylinder or water tank
  • It can limit where you install the boiler since the cold-water cistern needs to be directly above the boiler.

Pros of System Boilers

  • The hot water storage cylinder makes them ideal for high hot water demands.
  • They don’t require a cold water cistern, meaning you require less space than a regular boiler with more flexibility on installation location.
  • They don’t require any components in the attic, and you don’t have to worry about freezing or potential leaks.

Cons of System Boilers

  • The hot water flow rate in your home will depend on the pressure of the main supply.
  • The high-pressure nature makes it unsuitable for properties with older systems
  • They need a hot water storage tank, meaning you need to find adequate storage space.
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Sizing A Boiler For Your 3 Bedroom House

The boiler size refers to the output and is measured in kilowatts (kW).

To determine the boiler size you require for your home, use the following formula to estimate:

  • 1 kW for towel radiators or small radiators.
  • 1.5 kW for averagely sized radiators.
  • 2 kW for large radiators.

Add the above scores according to the number of radiators in your home to get the total kW you require.

Factors To Consider for The Best Boiler For A 3 Bedroom House

  • The overall brand reputation from customer reviews.
  • The warranty period offered by the brand.
  • The price range of the boilers. The cost of the boiler doesn’t always mean it’s better.
  • Boiler efficiency ratings.
  • Customer service performance.
Boiler upgrades

What Are Condensing Boilers?

Condensing boilers recycle the heat from waste flue gases to preheat the water entering the boiler.

Boiler legislation established in 2005 in response to increasing environmental and energy costs concerns mandates all new boilers to be condensing for vast improvements in boiler efficiency.

All modern boilers are condensing, including combi, regular and system boilers, and the sale of non-condensing boilers is banned in the UK.

Check out our boiler brand price guides and comparisons:

Best Boiler for a 3 Bedroom House Final Thoughts

The best boiler for your three-bedroom house will depend on various factors, including your property size, the hot water demands, and available water pressure.

Most UK homes use gas combi boilers followed by regular and system boilers.