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Which is the Best Boiler for a Small House or Flat?

Adam Cherry
By: Adam Cherry
Updated: 30th September 2021

Best Boiler for a Small House or Flat

In a small house or flat with 1 bathroom and around 10 radiators, a combi is the perfect boiler. They're highly efficient, heat water on demand and don't take up much space.

As there are so many benefits to installing a combi boiler, every manufacturer has their very own range. This can make it hard to know where to start. So, to help, we've compared the most reliable gas combi boilers from trusted brands that are perfect for small homes or flats.

Best Gas Combi Boiler: Ideal Vogue Max C26 vs Vaillant ecoTEC Plus 825

If you live off-grid, then an electric combi is worth considering.

Best Electric Combi Boiler: Elnur Mattira vs Electric Heating Company Comet

Live in a bigger property? Then compare the best boilers for a 3 bedroom, 4 bedroom or 5 bedroom house.

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What is a combi boiler?

Combi Gas Boiler
For small houses and flats, there's no better heating system than a combi boiler.

There are three types of boiler: combi, system and regular. Combi boilers are the only one which don't need any external parts (tanks in the loft or a hot water cylinder). This makes them compact heating systems so the only space you'll need to commit is a spare cupboard in the kitchen.

As well as being compact, they take hot water straight from the mains. This means they can act fast when you need heating or hot water.

The only downside is that by not storing domestic hot water in a cylinder – as regular and system boilers do – they can't meet high demands for heating. Which is why they’re great options for small houses and flats with one bathroom.

Best gas combi boiler: Ideal vs Vaillant

Ideal and Vaillant are amongst the most popular and trusted boiler brands around.

Let's start this head-to-head by getting to know both boilers a little better, find out their key features in the table below:

Boiler Feature Ideal Vogue Max C26 Vaillant ecoTEC Plus 825
Central Heating Output 18 kW 20.4 kW
Domestic Hot Water Output 26 kW 25.4 kW
Seasonal Space Heating Efficiency Rating 92.7% 94%
ErP Efficiency Rating A Heat, A Water A Heat, A Water
Flow Rate 10.6 l/min 10.5 l/min
Standard Warranty 10 years 5 years
Maximum Extended Warranty 12 years 10 years
Dimensions in mm (HxWxD) 740 x 445 x 330 720 x 440 x 338
Mounting Wall-mounted Wall-mounted
Typical Price £1,089 £1,152
Typical Installation Costs £500 - £1,000 £500 - £1,000


The efficiency rating of a boiler tells you how well it turns fuel into heating and hot water. The higher the percentage, the less fuel it will need to heat your home.

Since Boiler Plus was introduced in 2018, all combi boilers must achieve efficiency levels of at least 92%. This means that all modern combi boilers are highly efficient and there really isn't much to separate them.

The Vaillant ecoTEC Plus 825 edges out the Ideal Vogue Max in this head-to-head with an efficiency of 94% compared to 92.7%.

Essentially, these percentages show you how much of each £1 you spend heating your home goes to waste. So, for every £1 spent heating a home with a boiler that's 94% efficient, only 6p is lost to the heat carried out of the home by waste gases.

Sizing (Output Rating)

Boiler Size
Boilers for small houses and flats are often too powerful. Which can lead to higher energy bills. So, to avoid that, you need to get boiler sizing spot on.

Boiler sizing is known as the output rating and is measured in kilowatts (kW). This is essentially a measurement of the boiler's power. Combi boilers have a separate output rating for central heating and domestic hot water. Both need to match the demands of your home.

In terms of the central heating output, the ecoTEC Plus 825 is slightly more powerful. 20.4 kW compared to 18 kW for the Ideal Vogue Max C26. Both of these are well suited to small homes and flats with around 10 radiators.

They can also meet the hot water demands of homes with 1 bathroom thanks to a DHW output of 26 kW for the Vogue Max C26 and 25.4 kW for the ecoTEC Plus.


Now warranty is a great way to compare boilers. During the warranty period, the manufacturer will take a look at any faults and fix them if they're the result of the manufacturing process. Checking the length of the warranty can give a good indication as to how long you can expect the boiler to run reliably.

Ideal offers a standard warranty of 10 years on the Vogue Max, which is twice as long as the ecoTEC Plus warranty. Both manufacturers make it possible to extend the warranty when certain terms are met. So you could get a 10 year warranty on the Vaillant ecoTEC Plus or extend the Vogue Max warranty out to 12 years. Both very lengthy periods of time.


In terms of price, there isn't much to separate these boilers. The average price of both is a little over £1,000 and the installation costs are likely to be very similar too. We recommend comparing quotes to find the best deal on the installation of a new combi boiler.

More gas boilers for small houses or flats

While the Ideal Vogue Max C26 and Vaillant ecoTEC Plus 825 are great options for small homes or flats, they're not your only options. ATAG, Baxi and Worcester Bosch also have combi boilers well worth considering.

Boiler Model CH Output DHW Output Typical Price
ATAG IC24 23.2 kW 26.6 kW
Baxi 825 21.2 kW 25 kW £858
Worcester Bosch Greenstar 2000 20 kW 25 kW £730

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Best electric boilers for a small house or flat

Millions of homes across the UK aren't connected to the gas network. This completely rules out the installation of a gas boiler. The common alternative is an oil boiler but that means storing the fuel in a bulky tank. Not every home has room for that. So for small homes or flats that are off-grid, an electric boiler is worth considering.

Electric boilers are compact, simple to install and incredibly efficient. An electric boiler is able to convert all of the electricity into heating and hot water without releasing carbon into the atmosphere. However, electricity is an expensive fuel – particularly when compared to gas and oil.

We've compared two of the most popular electric boilers on the market to help you find the right model for your home: Elnur Mattira vs Electric Heating Company Comet.

Elnur Mattira vs EHC Comet

We've compared two of the most suitable electric combi boilers for a small house or flat. Take a look at their key information below.

Boiler Model Elnur Mattira Electric Heating Company Comet
Output Rating 12 kW 14.4 kW
Efficiency Rating 100% 100%
Efficiency Band Rating D D
Standard Warranty 2 years 2 years
Mounting Wall-mounted Floor-standing
Dimensions in mm (HxWxD) 830 x 555 x 450 1,745 x 580 x 630
Typical Price £2,370 £2,500
Typical Installation Costs £500 - £1,000 £500 - £1,000

Energy Efficiency

One of the biggest benefits of installing an electric boiler is their efficiency. These boilers are both 100% efficient. This means that all of the electricity they use is turned into heat for your home or hot water. No waste whatsoever.

Plus, as they don't burn fossil like gas or oil, electric boilers don't emit carbon into the atmosphere.

However, you'll notice that both of these boilers have an efficiency band rating of D. That's despite being 100% efficient. The reason for this is due to electricity production being considered carbon intensive. This is because fossil fuels are being burned to create electricity which does produce carbon.

Times are changing though and renewables, like solar and wind, are producing more electricity than ever before. And this doesn't emit carbon. So, as renewable electricity production continues to grow, we may see the band rating of electric boilers improve.

Read more in Electric Boiler Efficiency Explained.


Both of these boilers come with a 2 year warranty as standard. Alongside this warranty for the unit, the hot water cylinder is covered too. Elnur offers a 5 year warranty on the cylinder while the EHC Comet comes with a warranty that's twice as long as 10 years.


The EHC Comet is the more powerful of these two boilers. It has an output rating of 14.4 kW which, for an electric boiler, means that it can meet the heating demands of a home with up to 10 radiators.

The Elnur Mattira has an output rating of 12 kW which is ideal for properties with between 6-8 radiators.


In terms of price, there isn't much to separate these electric boilers. The Elnur Mattira is likely to be the most affordable option but both are priced around the £2,500 mark.

Best electric boiler for a small house or flat

For a home with fewer than 10 radiators then a boiler in the Elnur Mattira range is a great option. As well as being highly efficient, they're compact units, quite a bit smaller than the EHC Comet models. This not only means they take up less space, they'll also be easier to install.

If you need an electric boiler capable of heating 10 radiators then this EHC Comet model is the right choice. Like the Elnur Mattira, it's highly efficient but it also has a longer warranty on the cylinder.

Gas or electric: Which is right for your home?

Blaze: Best Gas Boilers
The gas combi boilers we've compared tend to come at a much cheaper price than the electric boilers and won't cost as much to run. This in itself could be enough to make your mind up.

If you live in one of the 2 million homes across the UK that aren't connected to the gas network then going electric is the next best solution. While the models might often be more expensive, they're cheaper to install, have almost no noise during operation and can reach efficiencies of 99%.

Get free boiler quotes today

After finding the right boiler for your home, gas or electric, you'll need a qualified engineer to carry out the installation. Installation costs can vary massively from installer to installer which is why we're here to help you get the best deal possible.

Complete one of our simple online forms and you'll get free quotes from up to 3 trusted engineers in your local area. You can then compare the quotes and decide which one to go with.

Adam Cherry

About the author

Adam Cherry

Adam is our resident home heating expert. His experience and advice has helped millions of customers improve the efficiency of their homes and save money.

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