Warranty People: Simple, Reliable & Straight Forward Cover For All Your Home

Choosing the right size or power of your boiler is just as important as choosing the right type of boiler. There is no convenient rule of thumb as to what size boiler would be the perfect fit for your home. The most commonly used type of boiler in small houses or flats is usually a combi boiler. This type of boiler is compact, easy to install, and does not take up too much space. However, that still does not tell you what size boiler you would need.

Choosing the Best Boiler for a Two Bedroom House or Flat

A good way to figure out what size boiler you need is to look at some basic points. But before we do that, let us first look at what “size” really means. It does not necessarily mean a larger surface area. Size is actually an interchangeable term for output.

Size/Output Explained

The size or output of your boiler is measured in kilowatts or kW. , the higher the output or kilowatts, the more powerful your boiler is. Choosing the right “size” of the boiler means choosing the one with sufficiently powerful output to heat your home. In this case, you need to choose a domestic boiler for a two-bedroom house or flat.

In the United Kingdom, there are a number of domestic boilers to choose from with power varying from 24 to 42kW. This makes the job of choosing the right boiler slightly more confusing because of the huge number of choices. It is easy to make two kinds of mistakes. You can either try to save money and end up with a boiler that is not powerful enough to heat your home. Alternatively, you are tempted to buy the most powerful boiler out there and end up with something that is expensive to run and maintain.

Choosing the right balance between price and output is very important. When buying a boiler for your two-bedroom house or flat, you want to get a boiler with the most suitable output at the best price.

How to Choose the Right Size?

People often end up asking questions about what is the most suitable type of boiler for a semi-detached or terraced residence. These can seem like very valid queries, but in reality, installers look at a different set of indicators.

When recommending the right size boiler for your home, an installer is more likely to consider the following:

  • The number of people in your home
  • The number of radiators in your home
  • The number of bathrooms in your home

Most installers rely on roughly the above factors to decide what boiler would suit you best. A two-bedroom house or flat is likely to have one bathroom, and at most four radiators. Based on this, the most suitable boiler size should be between 24-27kW.

A combi boiler with an output of 24 kW can easily run up to 10 radiators. It can also comfortably supply hot water to one bathroom at mains pressure. Best of all, a combi boiler does not take up much space, so you do not have to worry about your living space shrinking.

Types of Combi Boilers

So, you know you need a combi boiler with an output between 24-27kW. But there are still other things to factor in, such as what type of combi boiler you should get. There are three types of combi boilers:

  • Gas-powered
  • Oil-powered
  • Electric

Gas combi boilers use your gas connection to heat water. If you live in a house or apartment connected to the gas network, a gas combi boiler should work best. Gas is relatively cheaper than other fossil fuels and is readily available across the United Kingdom. A gas combi boiler is easy to install and can supply heating to your home easily.

An oil combi boiler uses oil to heat water and supplies it to radiators and taps. It works similar to a gas combi boiler and requires a constant fuel source. A gas combi boiler gets this from your gas connection. It will be different for an oil combi boiler. You will need a tank of oil, as well as a fuel-supplier to keep it topped up. Oil combi boilers are useful when you live in a home without a connection to the gas network.

Electric combi boilers are popular in British homes without access to gas or oil. Electric combi boilers have an almost 100% efficiency and do not have any harmful emissions. This is because they use electricity to heat water instead of fossil fuels. However, since electricity is not cheap, an electric combi boiler will drive up your energy bills. However, it is still one of the best choices if you don’t have access to a gas network or an oil supplier.

The Best Boilers in the Market

The following table shows some of the best domestic boilers for a two-bedroom home or apartment:


Size Type Efficiency Warranty *Price

Viessmann B2KB Vitodens 200-W

26kW Gas Combi Boiler 97.9% 3-5 Years


Grant Vortex Pro Internal

26kW Oil Combi Boiler 94.5% 2 Years


Ferroli LEB TS 12kW Electric Combi Boiler 99.5% 2 Years


*All prices and specifications are accurate as of the time of this writing 5.8.2019

Energy Efficient Boilers

When looking at the output and price of the boiler, a very important factor is to consider its energy efficiency. The more energy efficient a boiler is, the less energy it wastes when heating your boiler. UK and EU regulations require a very high standard of efficiency from new combi boilers.

The Viessman B2KB Vitodens is one of the most energy-efficient domestic combi boilers on our list. It has an energy efficiency of 97.95%. That means less than 3p go to waste for every £1 you spend on heating. The Grant Vortex has an efficiency of 94.5%, meaning that out of every £1 less than 6p goes to waste. The Ferroli LEB TS has the highest efficiency at 99.5%. This means less than 2p is wasted out of every £1 you spend on heating.

The energy efficiency of the boiler you consider for your two-bedroom home is very important. The higher the boiler’s energy efficiency, the more you save on your energy bills. Because high-efficiency boilers waste less energy, you are not spending much more than you need to supply heat to your home.

Energy efficiency also has a more important impact. Less efficient boilers waste heat and have harmful emissions that increase your carbon footprint. Newer combi boilers are condensing boilers that reuse flue gases to heat water efficiently. They are eco-friendlier with a smaller carbon footprint than older, inefficient boilers. 

Warranty Period – Why It Matters

Most boiler manufacturers offer standard warranties or guarantees with their boilers. Warranties offer assurance to buyers that the manufacturer stands by its boiler. It also helps protect you against unexpected breakdowns during the warranty period.

The specific conditions of your warranty will vary based on your choice of manufacturer and boiler. However, most warranties generally become void if:

  • You do not get the boiler serviced
  • You do not get it installed by an accredited installer
  • Damage to the boiler through poor workmanship
  • Damage to the boiler due to DIY projects
  • Getting the boiler repaired or serviced by an independent or unregistered engineer

Most warranties offered by boiler manufacturers include an annual service. An annual service helps maintain the boiler’s good working condition. It also helps identify any minor faults that could turn into major problems with time. An annual boiler service is very important if you want to extend the standard warranty that comes with your boiler.

Other Factors to Consider

There are a number of factors to consider other than the number of bedrooms or bathrooms in your home. These can help you make a smarter choice as to what boiler would work best for you. The factors include:

Knowing your current boiler size can be a useful starting point. However, you do not always have to get the same size as your existing boiler. Your household needs may have changed since the boiler was installed. You could have a higher water demand or your insulation could have degraded. You may even be thinking about converting a loft into an extra living space. Based on these factors, you need to consider if your current boiler provides enough hot water for your needs. In many cases, this may indicate if you need a larger boiler size. If your boiler is 8 years old or more, it has likely become inefficient and may require replacement.

You need to make sure you get the right type of boiler for your apartment. There are three major types of boilers: Regular, System and Combi. You also need to make sure you choose the right fuel source, whether gas, oil or electricity. Combi boilers are well suited to smaller homes such as two-bedroom houses and apartments. For larger homes, you may need to consider a system or regular boiler instead. These come with a hot water cylinder to store the heated water for use on demand.

Your mains flow rate is a very important factor to consider, especially when getting a combi boiler for a small home. Combi boilers take their water supply directly from the water mains. The size of your combi boiler should be sufficient so that it can cope with the mains water pressure you get. The mains flow rate is how many liters of water flow through your boiler in one minute. Most boiler manufacturers specify the maximum flow rate of their models, which lets you know which one to choose. The higher your flow rate, the larger the size your boiler needs to be. 

Tips to Maximize Boiler Efficiency

Most new combi boilers are very efficient, thanks to the high standards set by UK and EU regulations. However, there are several things you can consider to maximize the efficiency of your boiler. These include:

  • Investing in insulation that is more effective. Poorly insulated homes lose heat faster, making your boiler work harder and driving up your energy bills.
  • Making sure radiators are of adequate size. Radiators have varying outputs, which increase with the size of the radiator. Make sure you have large enough radiators to heat your rooms quicker and waste less energy.
  • Investing in smart boiler controls. The Internet of Things has a number of applications in heating. Smart controls allow you to control your home’s temperature through a smartphone app. You can even see how much energy your house is consuming and control it to reduce wastage. The higher-end systems automatically adjust room temperature based on the weather outdoors.
  • Getting your boiler serviced annually. An annual boiler service by a professional is essential for the long life and efficiency of your boiler. It helps identify problems early on that could make your boiler inefficient in the long run.


To conclude, the price of a new boiler should not be your only consideration for your two-bedroom house or apartment. You need to know the number of radiators, bathrooms, and people in your home to assess your hot water needs. These will help you decide the correct size for your new boiler, especially if your old one is inefficient or cannot handle your needs.

To get the most out of your boiler, be sure to get it serviced at least once a year by a professional. This will not only extend the manufacturer’s warranty but also keep it in good working condition. Be sure to invest in good home insulation to reduce heat wastage. Check if your radiator-size is adequate to heat your room quickly. 

For a small, two-bedroom house or apartment, a combi boiler between 24-27kW works best. You need to make sure you choose the right fuel type, between gas, oil, and electricity. Knowing your mains flow rate is also important, as it will dictate what type of boiler to choose to handle it. Finally, a combi boiler with a high-efficiency rating will help you save on energy bills. For larger homes with more bedrooms and bathrooms, you may need to consider a regular or system boiler.

Which Is the Best Boiler for a Two Bedroom House or Flat

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