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Finding a boiler for a small home or flat with a single bathroom is equally important as finding a boiler for a larger home. If you end up installing a boiler that is too powerful, you will see an increase in your energy bill.Small homes with 1 bathroom and 10 radiators can get enough hot water and heating from a gas combi boiler. These units are compact since they don’t have tanks that need extra storage. Combi boilers provide hot water on demand and hence they are energy efficient.

Basics of Boiler Size

Before determining what boiler is best for your small house, it’s important to understand how the size of the boiler is measured. The size refers to boiler output in terms of kW (kilowatts) not its physical dimensions. KW measures the energy output a boiler produces in the form of heat. The more heat and hot water you need, the higher the output you require.

A Bigger Boiler is Not Always Better

You must have read and heard that a high-efficiency boiler can reduce your energy bills. Unfortunately, you won’t see a lower energy bill if the components of your central heating system are not sized correctly. In other words, a bigger boiler will not necessarily save you money.

To make the central heating system run at optimum efficiency and save maximum on the energy bills, install a boiler of the right size in the house. Most homeowners assume a big boiler is better. They want to get a plentiful supply of hot water assuming that a bigger boiler will heat the water more efficiently than a smaller one.

This is an inefficient way of choosing a boiler. Bigger boilers produce higher output and they are more expensive. In operation, when the boiler output does not match the demand of the household, it will run for a short period and then turn off. The frequent cycle of start and stop to meet the hot water needs of the house consumes more energy.

An oversized boiler, therefore, raises energy bills and you will have to pay for repairs in the long run. The boiler and its components will heat up often to meet the energy needs of the house.

Boilers for Small Homes and Flats

Combi boilers are sold in different outputs. You can choose the kW rating depending on the number of bathrooms in the house. Generally, combi boilers are available 3 different sizes:

  • 24 to 27 kW: A small house or apartment with 10 average-sized radiators and one bathroom will require a combi boiler that produces 24 to 27 kW output.
  • 28 to 34 kW: If you have a medium-sized house with 2 to 3 bedrooms and up to 15 radiators, you will need a 28 to 34 kW combi boiler.
  • 35 to 42 kW: It’s a rule of thumb, the higher the hot water demand, the higher the boiler kW is required. This will ensure everyone in the house gets a good flow rate of hot water.

How to Know What Boiler Size You Need?

In the past, homeowners were advised to buy an oversized boiler for compensating the heat loss. This is no longer recommended. If you do so, you will be wasting energy. To determine the right boiler size, you must determine your needs. Such as:

Hot water demand: If you have a small house with one bathroom, your hot water needs will be limited. A combi boiler that provides hot water on demand will suit your needs. The heat load on an average home varies from 10 to 20 kW.

The number of radiators: The number of radiators in the house also affects your decision of determining the size of the boiler. An average house with 2 to 3 bedrooms has around 10 radiators. They require a small to medium combi boiler with 24 to 30 KW output. That means if you have more than 10 radiators, you will need a combi boiler with a greater output.

Water pressure: This is not a concern for modern houses that run on the mains water supply. Some old homes don’t have a high-pressure water supply. This can impact the size of the boiler you choose. A combi boiler typically is sufficient to cope with the amount of water passing through it that needs to be heated.

If you need a higher flow rate, you will need a bigger boiler. Most manufacturers now provide information on the flow rates of their boilers. In case you are confused, you can call an engineer to help you choose the most economical boiler for your household.

Best Boilers for Small Homes and Flats

Check out some of the most popular boilers for small homes from leading boiler brands:

Ideal Logic+ 24 Combi: Ideal started in 1906 and that makes it one of the pioneers of boilers. Their Logic+ series are their best-selling range. Ideal Logic+ 24 Combi is known as the most efficient and compact boiler of them all. The Ideal logic+ has been awarded the Quiet Mark Certification. These boilers don’t make noise while operating.

Ideal Logic+ 24 Combi is a small boiler that is 700mm high. It comes with a 2-year manufacturer warranty covering parts and labor. Its central heating output is 24 kW. The flow rate is 9.9 liters per minute which are perfect for small houses. Its ERP (energy efficiency) is 94 percent which makes it an A grade for efficiency.

Vokera Easi-heat Plus 25c combi boiler: Vokera is leading manufacturers of domestic gas boilers, water heaters, light commercial gas boilers, heat pumps, and solar thermal collectors. They established over 35 years ago and they specialize in offering a complete home heating package.

Vokera Easi-heat Plus 25c combi boiler is a versatile and compact unit. It is so small that it can fit in the kitchen cupboard. This lightweight boiler is ideal for small homes. Its central heating output is 25 kW. It comes with a 5-year warranty and ErP Class A rating to meet your energy efficiency needs.

Potterton Titanium 24kW combi boiler: Potterton has been making boilers from 1850. Their boilers have the reputation of being easy to use and dependable. They use the latest technology to build their boilers. They also meet energy efficiency requirements.

Titanium 24kW combi boiler is a wall-mounted combi boiler that’s A-rated for its efficiency. Its central heating output is 24 kW with a flow rate of 11 liters per minute. Potterton Titanium 24 kW combi boiler comes with 7 years warranty on parts and labour.

Factors to Consider When Getting a Boiler for Small Property

When you are buying a boiler for a new property, you need to consider the water flow rate and heating output. You have to be sure the heating system is capable of generating necessary heat output without compromising on the performance.

Logically, if you have a small property, then you can invest in a boiler that generates a low level of heat energy. Your home will heat up faster. Similarly, you won’t need an excessive flow rate. It is best to discuss these aspects with a gas certified engineer before purchasing the boiler.

Another important thing to consider is space. Go for an entry-level system that is small in size. An ideal boiler is the one that can fit into a cupboard.

Why Choose A Combi Boiler for Small House?

A combi boiler does not need a hot water tank or a water storage facility to operate. Their compact size makes them ideal for homes with limited storage space. That’s why many households in the UK are upgrading their old boilers with combi boilers.

By choosing a combi boiler, you no longer have to worry about high energy bills. The unit saves energy by providing hot water on demand.

Cost of Small Boilers

According to uSwitch, you should expect to pay £500 to £2,500 for a new boiler. When you are getting a new boiler, along with the price of the boiler comes the cost of installation. The installation quotes can vary based on:

  • Labour required: If you are calling engineers from a large national company and you live in an area where the cost of living is high, you have to pay a higher price for labour. To cut this expense, call a local installer.
  • Materials: If there is a need for additional parts and materials when installing the boiler, this will increase the installation cost.
  • Upgrades: Sometimes, with new boiler installation comes upgrading. Upgrades can cost a lot of money.

Where to Place a Boiler in a Small House?

Boilers are sealed unit and so you can place them anywhere in the house if it does not validate the building regulations. These are your options when it comes to boiler placement:

Utility room/cupboard: If you have a utility room, it’s best to install the boiler there. If the utility room is located close to the kitchen, you will get better a flow rate.

If you don’t have a separate utility room, that’s not a problem. You can place the boiler in the kitchen cupboard. Modern boilers are small in size; therefore, it might be easier to fit yours in the cupboard.

Loft: The loft also makes for a great place to install a boiler. Before you do that, make sure you have convenient access to the loft and adequate lighting. Fit the boiler to a wall that is capable of supporting the weight. If there is restricted space in the loft, so much that a person cannot stand up straight, don’t install the boiler there. When it is time to call an engineer for annual service or repairs, it will be difficult for them to get in.

Bathroom: You can also install a boiler in your bathroom. However, it’s not recommended because some boilers make noise and this can disturb the sleep of homeowners.

Tips for Buying the Right Boiler for a Small House

Buying the right boiler for your smart house or apartment is a decision you would not want to compromise. These tips will help you pick the right one:

Output and flow rate: You have to ensure the output and flow rate of the boiler is suitable for your property. Small homes don’t need a boiler with a higher central heating output. If you buy a boiler that produces higher output than needed, this will increase your energy bill. Call a heating engineer to determine the water pressure in your apartment. You will get the ideal flow rate required for your house and then you can buy the right boiler according to that information.

Size: If you have a small flat, you would appreciate having extra space. It is a good idea to install a compact combi boiler in this case. They are small enough to fit inside the kitchen cupboard. When buying a boiler, aim for the one that can fit in your available space.

Guarantee: When getting a new boiler for your home, make sure it’s parts and labor are covered. Usually, boilers come with 5 years guarantee.

Environmental friendliness: If you are getting an A-rated boiler, it will bring great value for money. Your energy bills will reduce and there will be a reduction in carbon footprint too. Choose an environmentally friendly boiler.

Good reputation: Check the reputation of the boiler brand. If a lot of people are complaining about recurring problems, this means the brand is not trustworthy. Pay attention to how the brand handles customer complaints.

Availability of parts: It is important that the parts of the boiler you are purchasing are readily available. You can also check with an engineer before making the final decision.


When shopping for a boiler for your house, keep the demand for hot water and flow rate into consideration. Call an engineer to determine the right boiler size for your household needs. For a small apartment with 1 bathroom and 10 radiators, a boiler that produces heating output anywhere between 24 and 27 kW is ideal.

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