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What Boiler Size For 4 Bedroom House?


Indeed, there are several important factors you have to consider before deciding on the best gas boiler for your 4 bedroom house.

Of course, size is up there among the most important factors. Your unit should be powerful enough to meet your household’s central heating and hot water demands.

Best combi boiler for 4 bedroom houses

Viessmann Vitodens 100W 35kW Boiler

This Viessmann boiler is a “Best Buy” award-holder that has successfully competed with other boilers from big 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.

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 35kW 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 4 bedroom houses

Valiant ecoTech Plus Boiler

The model offers several output variations. We recommend the 30kW 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 4 bedroom houses

Worcester Bosch Greenstar 24Ri Regular boiler

Trust us, there’s nothing “regular” about this quality boiler. It has been the “Best Buy” champion for 7 consecutive years. The Greenstar line has several variants in the market. In our opinion, the 24kW unit is ideal for 4 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 £2000.

Below are some other factors that are related to boiler size:

  • The boiler type.
  • It’s physical size. Dimensions.
  • The boiler’s efficiency rating.
  • Industry-standard warranty.

Types of boilers for a 4 bedroom house

Indeed, not all boilers are the same. 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.

When we talk about “boiler size,” we’re not referring to its physical attributes. Instead, we are referring to the boiler’s output power. Kilowatts per hour (kWh) is the most widely used metric for describing a boiler’s heating ability. One kilowatt is 1000 watts. Therefore, a 35kW boiler means it produces 35,000 watts of heat energy per hour of operation.

Of course, house size is directly proportional to boiler size. The bigger the house, the more powerful the boiler needs to be.

Likewise. the more the occupants, the higher the demand for hot water. Therefore, the boiler needs to be big enough to meet the demand.

4 bedroom houses usually fall in the “medium-sized” home category. Usually, we expect them to have one to two bathrooms. As far as the demand for hot water is concerned, we expect it to be average to slightly above average.

Combination boilers

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

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

Because of their “instant” hot water production, Combi boilers don’t need separate hot water tanks. Therefore, they take up less of your precious space. Combi boilers are ideal for houses where space is a scarce resource.

Are Combi boilers good for 4 bedroom houses?

If your home has one to two bathrooms, then yes. However, combi boilers might not be the best option if your house has three or more bathrooms.

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

However, there is no need to worry if you are a big fan of combi boilers. We are pleased to announce that there are some Combi boilers with the required output for 4 bedroom houses.

Ideally, for a 4 bedroom house, we advise you to buy a boiler with an output of about 35kW to 45kW. The number of radiators in your home will also affect the boiler size. If there are up to 15 radiators, then a 35kW-boiler is ideal. For a larger house with up to 20 radiators, then a 45kW combi boiler is perfect.

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 the boiler to re-heat the water and re-fill the cylinder.

Additionally, system boilers are more wasteful than combi boilers since the water in the storage tank will cool down when unused. Later on, the boiler might end using more energy to re-heat the water.

Are system boilers good for 4 bedroom houses?

Yes, their hot water storage tanks enable them to simultaneously supply several users with hot water. Ideally, you’ll need a system boiler with an output rating of around 24kW and 30kW. The 24kW variant suits 4 bedroom houses with 1 to 2 bathrooms. On the other hand, the 30kW unit can comfortably handle more than 3 bathrooms.

Regular boilers

You might also know them as Conventional or Heat-only boilers. These are the longest surviving boilers available in the market.

Regular boilers are more or less the same as system boilers. However, there is one major difference. Unlike, System boilers, they don’t have a dedicated hot water heating system. Regular boilers solely rely on the central heating system. It needs at least two tanks. One to supply water to the central heating system, and another to store heated water.

Are regular boilers good for 4 bedroom houses?

Just like system boilers, Regular boilers are also 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.

Unfortunately, they also share the same drawbacks as system boilers. Once the hot water runs out, you’ll have to wait for the tank to refill.

For a 4 bedroom house, you need a Regular boiler with an output of around 27kW to 40kW. Likewise, you’ll also need a bigger hot water tank if the hot water demand is high. Nonetheless, a 250 to 300-litres water tank should be enough.

Take Note: Despite the recommended boiler sizes, you’ll always need a more powerful boiler if there are a significant number of people in the household.

Likewise, you also be keen on your house’s insulation state. If your house is poorly insulated, the rate of heat loss will always counter the work done by your boiler. Therefore, make sure is 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 more heating costs.

What look for when choosing a boiler for a 4 bedroom house

Good. So you’ve now known the ideal boiler size for your 4 bedroom house. Next, we’ll decide on some of the factors to look for in individual boilers.


It’s simple. There more efficient the boiler, the more you’ll enjoy spending less on heating expenses. Ideally, you want an “A Grade” unit. Its efficiency should not be below 89%. With the right boiler, you can save up to £310 per year on heating expenses.

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


Long live your boiler! Nonetheless, you should be prepared should the unexpected happen. We know that boiler insurance can be expensive. Therefore, we’re advising you to capitalize on boiler warranties. Make sure it’s nice and long. Ideally, buy a boiler with a minimum warranty period of 5 years.

Physical size

Depending on your property, size might be or might not be a big issue. Nonetheless, we know for aesthetic purposes, most people prefer neat and compact units. These days we even have boilers that can fit in kitchen cupboards.


There is no simple one-word answer for the “best boiler size for 4 bedroom houses.” There are a lot of factors to consider before coming up with a suitable figure. Hopefully, this article has helped you make the right decision.

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