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What Boiler Size For a 3 Bedroom House?


Deciding on the best boiler size can be challenging. Don’t worry. We’re to help you with that.

First and foremost, there are several important factors you have to consider before deciding on the best gas boiler for your 3 bedroom house.

Of course, “size” is a big deal. The unit should be powerful enough to meet your household’s central heating and hot water demands.

Best combi boiler for 3 bedroom houses

Viessmann Vitodens 100W 30kW Boiler

We present to you a “Best Buy” award-holder that has successfully competed with other combi boilers from reputable companies like Worcester Bosch.

It’s an “A Grade” stainless steel gas boiler with an efficiency rating of 89.5%. Additionally, it supports internet connectivity and can link with smart thermostats for a smoother and money-saving experience.

Also, its hot water flow rate of 14.3 litres per minute doesn’t disappoint. Size-wise, this unit is compact and will fit in most kitchen cupboards.

We recommended the 30kW variant. However, if you’re interested, the model offers other more powerful options.

The total cost of purchase plus installation is around £2,500.

Best System boiler for 3 bedroom houses

Valiant ecoTech Plus Boiler

The model offers several output variations. We recommend the 24kW version. Not only does it have an efficiency rating of 89.7%, but it’s also compatible with the vSmart app and several other smart thermostats.

Likewise, it’s also compact and tidy with the standard 5-year warranty.

For this “A Grade” boiler, you should expect to spend around £2,700 for the unit plus installation.

Best Regular Boiler for 3 bedroom houses

Worcester Bosch Greenstar 24Ri Regular boiler

There’s nothing “regular” about this quality boiler. It has been the “Best Buy” regular boiler for 7 consecutive years.

The Greenstar line has several variants in the market. In our opinion, the 24kW unit is ideal for 3 bedroom houses with up to 10 radiators.

The 24Ri boiler is also “A Grade” with an efficiency rating of 89.2%. Additionally, it’s also neat and compact enough to be wall hung or installed in a kitchen cupboard. Also, it’s compatible with several programmable thermostats.

The total cost of the unit plus installation is around £2,000.

Below are some other factors you should consider that are related to boiler size:

  • The boiler type.
  • Physical size (Dimensions).
  • Its efficiency rating.
  • Industry-standard warranty.

Before we get started, we’ll slightly touch on these factors to get them out of the way.

What look for when choosing a boiler for a 3 bedroom house

Efficiency rating

It’s simple. There more efficient the gas boiler, the less you’ll spend on heating expenses. Ideally, you want an “A Grade” unit with an efficiency rating above 89%. Choose correctly, and you can save up to £310 per year on heating expenses.

Additionally, we have other “extra” features that can help you capitalize on your boiler’s efficiency. A good example is the integration of smart and programmable thermostats. Not only will life be more convenient, but you’ll also be able to reduce heat waste and saving more money in the long run.

Warranty Period

Cheers to your boiler’s long life!

Nonetheless, you should be prepared for the worst-case scenario. We know boiler insurance can be expensive for some people. Therefore, we’re advising you to capitalize and save money on boiler warranties. Make sure it’s nice and long. Ideally, it should be not less than 5 years.

Physical size

As things get smaller, physical size has slowly become a big deal for most homeowners. For aesthetic purposes, most people prefer neat and compact units. These days we even have boilers that can fit in kitchen cupboards.

Types of boilers or for a 3 Bedroom house

In case you didn’t know, boilers come in different shapes and sizes. Although they all work to heat our homes and provide us with hot water, they significantly differ in how they go about their business. Currently, there are three main types of boilers:

  • Combination boilers.
  • System boilers.
  • Regular or Heat-only boilers.

“Boiler size” doesn’t refer to physical attributes. Instead, it’s an attribute that explains a boiler’s output power. Kilowatts (kW) is the most widely used metric for describing a boiler’s output ability. One kilowatt accounts for 1000 watts. Therefore, a 30kW-boiler produces 30,000 watts of heat energy per hour of operation.

As you might have guessed, house size is directly proportional to boiler size. The bigger the house, the higher the boiler output should be.

Likewise. the more the occupants, the higher the demand for hot water. If your house has several occupants (+5), you’ll need a relatively more powerful boiler.

  • 3-bedroom houses usually fit the “medium-sized” category. Usually, we expect them to have one to two bathrooms.

A three-bathroom house is an outlier.

Combination boilers

Combination boilers are also known as Combi boilers. They are currently trending because of their impressively high energy efficiency. Did you know that some combi boilers have efficiency ratings of up to 98%?

Additionally, combi boilers are also known for their “dual” trait. A standard Combi boiler combines both the central and water heating systems into one solid unit. That way, it can instantly produce hot water upon activation.

Because of their “instant” hot water production, Combi boilers don’t need separate hot water tanks. Therefore, they take up less living space. Combi boilers are ideal for small to average-sized houses and apartments.

Are Combi boilers good for 3 bedroom houses?

Yes. Most of the combi boilers are perfect for 3 bedroom houses with one to two bathrooms.

However, there be a problem if each bedroom has its separate bathroom.

As mentioned earlier, combi boilers produce hot water instantly without having to store it in a tank. If your home has several bathrooms, your combi boiler might struggle when it comes to simultaneously providing them with hot water.

However, there is no need to worry if you are a big fan of combi boilers. We are pleased to announce that some Combi boilers offer the required output for 3 bedroom houses.

For a 3 bedroom house, you need a combi boiler with a power output in the range of 28 to 34kW. Such a gas boiler should comfortably cater for up to 15 radiators and 2 bathrooms. If your house is rocking more radiators or bathrooms, you should consider getting a system boiler.

System boilers

Unlike combi boilers, system boilers have separated central and hot water systems. Also, they require storage cylinders.

For system boilers, the hot water supply isn’t instant. Usually, the system boiler will turn on twice a day, in the morning and evening.

Once it heats the water in the morning, it stores it in the cylinder for easy access. Thus, unlike combination boilers, it has no problem serving multiple occupants at the same time. However, if the water runs out, you’ll have to wait for it to re-heat the water and re-fill the cylinder.

Technically speaking, system boilers are more wasteful than combi boilers since the water in the storage tank will cool down with time. Later on, the gas boiler might end up using more energy to re-heat the water.

Are system boilers good for 3 bedroom houses?

Yes. Thanks to their hot water storage tanks, they can simultaneously supply several users with hot water.

For a 3 bedroom house, you need a system boiler with an output rating of around 18 to 24kW. It should be enough to handle up to two bathrooms.

You must have noticed that the required output rating for system boilers is less than that for combi boilers. This is because combi boilers tend to work harder than system boilers. Because of their “instant hot water feature,” combi boilers tend to turn on several times a day.

Regular boilers

Also known as Conventional or Heat-only boilers. These are the oldest boilers in the market.

Regular boilers are more or less the same as system boilers. However, there is one major difference. Unlike, System boilers, they lack a dedicated hot water system. Regular boilers solely rely on the central heating system. They need at least two tanks. One to supply water to the central heating system, and another to store heated water.

Are regular boilers good for 3 bedroom houses?

Regular boilers are more suited for larger houses than Combi boilers. Because of the hot water tanks, they have no problem simultaneously supplying hot water to several users.

For a 3 bedroom house, you’ll need a Regular boiler with an output of around 18kW to 24kW. The storage should have a capacity of at least 250 litres.

Note: You have to be keen on your house’s insulation. If your house is poorly insulated, the rate of heat loss will always counter your boiler’s hard work. Therefore, make sure it’s up to par as far as insulation is concerned. Pay attention to window and door sealing, loft insulation, and glazed windows. If you’re not careful, you might only incur unnecessary heating costs.


Indeed it’s not easy determining the accurate best boiler size for your 3 bedroom house. There are just too many factors to consider. Hopefully, this article has helped you make the right decision.

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