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Best Small Combi Boiler


If you live in a small property with little space to spare, you would want to invest in a small yet powerful boiler that would fit in the little available space. But how do you go about selecting a small boiler that is powerful enough to satisfy your home’s heating and hot water needs?

There is no doubt that the best heating system for small houses and flats is the combi boiler, which is compact, highly efficient, and heats water on an on-demand basis. Thanks to its small dimensions, a combi boiler can be stowed away into the tiniest space available in your home, such as a spare cupboard in the kitchen.

With every boiler manufacturer currently having its range of combi boilers, it suffices to say that selecting the best small boiler for your home might be more complicated than you expected. However, you shouldn’t worry as we have handpicked the most reliable gas combi boilers suitable for a small home or flat. We have also strictly covered boilers from trusted and reputable brands as they guarantee quality.

What is the difference between a small and a compact combi boiler?

If you are new to the boiler world, you will often find yourself confused by two terms commonly used in the industry; small and compact. Although you may occasionally hear people use the two terms interchangeably, they have entirely different meanings.

A small boiler is a boiler that yields a lower heat or power output (measured in kilowatts) than a traditional product. Although these boilers have a lower output, they can still meet a small property’s heat and hot water demands. Currently, the smallest boilers in the market have a power output ranging from 25 kW to 30 kW.

On the other hand, a compact boiler refers to a boiler with smaller dimensions than traditional products. As such, compactness, in this case, is determined by the dimensions of the boiler unit itself.  Therefore, a compact boiler is an ideal choice if you are looking for a small boiler unit that can fit into small spaces such as an empty kitchen cupboard.

Luckily, you won’t have to worry about the definition of the two terminologies, as most small boilers are designed to be compact. This is understandable given that small boilers are meant to be installed in small properties, which, more often than not, have little available space to spare.

Factors to consider when buying small boilers

  1. Efficiency Ratings

A boiler’s efficiency measures how well the boiler utilizes the supplied fuel to heat water for central heating and domestic use. Generally speaking, the higher the boiler’s efficiency rating, the less energy it will need to heat your home, and the lower the carbon footprint.

Currently, the most efficient boiler is the Ideal Vogue Max, with an efficiency rating of 94%. And to put this to context, for every £1 you spend heating your home, 94p will be converted to heat while only 6p is lost.

  1. Sizing (Output Rating)

Boiler sizing or output rating measures the boiler’s power, usually given in kilowatts (kW). The boiler’s output should be able to match your home’s heating demands, as an oversized boiler will waste energy while an undersized one will struggle to heat your home.

Combi boilers have two output ratings, one for central heating and one for domestic hot water. Before making a purchase decision, ensure that both the central heating and hot water output ratings of the selected boiler meet your home’s heating demands.

  1. Price

When it comes to price, you should settle for a boiler within your budget reach. Do not overstretch your budget by going for an expensive boiler brand, yet some budget boilers have a similar performance. However, steer clear of cheap boilers as they will cost you in repairs and sourcing for parts.

  1. The warranty period

A good warranty will cover replacement parts and repairs should your boiler develop some faults down the line. Ideally, the warranty period should be as long as possible, as it gives you peace of mind knowing that the manufacturer will repair or replace your boiler within a reasonable timeframe. The majority of the top brands offer boiler warranties ranging from 5 to 10 years.

  1. Availability of parts

There is always the possibility that your boiler will break down at one point in its lengthy lifespan.  And when this happens, chances are, you will need to replace a faulty component, be it the heat exchanger or the divert valve. You will need quick access to these parts to ensure that your boiler is up and running in no time. Hence, it would be best to acquire a boiler whose spare parts are easily accessible in the UK.

  1. Water Pressure

The water pressure in your mains water supply should be high enough to meet the boiler’s flow rate. Lower mains pressure means the pressure of the water coming out of your hot water outlets will be low, and you won’t be able to run two showers simultaneously. Luckily, most modern homes have a strong mains pressure, meaning any small boiler will be able to send water to your outlets at the designated flow rate.

Best Small Combi Boilers

Purchasing a boiler is a long term investment, given that the boiler you are buying today is expected to serve you for 10 to 15 years. It is, therefore, essential that you weigh all your options and make an informed decision when purchasing the small boiler that will fit your home.

Here is our shortlist of some of the best small boilers currently in the market.  These boilers have been thoroughly vetted based on factors such as reliability, efficiency ratings, customer reviews, and customer reviews.

Worcester Bosch Greenstar CDI Compact 28kW

Worcester Bosch is arguably the most famous boiler brand in the British boiler market, and it is only natural that it would produce some of the best boilers in each category. When it comes to small boilers, the Worcester Bosch Greenstar CDI Compact boiler is the undisputed champion, having won the prestigious Which? Best Buy Award for ten years running.

The boiler unit measures 690 x390 x 280 mm, meaning it can effortlessly fit into any standard kitchen cabinet or cupboard. Greenstar CDI compact boilers have a central heating output of 24kW and a hot water output range of 28kW, 32kW, and 36kW.

Worcester Bosch Greenstar CDI Compact boilers have a standard 7-year warranty but can be increased to 10 years. Despite being, by far, the best small boiler, the Greenstar CDI Compact 28kW boiler is a premium unit and costs around £2,095. It is, however, worth its price, coming with free wireless controls, a boiler filter, and free installation.

Viessmann Vitodens 100-W Combi Boiler

Viessmann is an established boiler brand that has dominated the UK and European boiler markets for quite some time. The brand is reputed for its impeccable German engineering and design.

The Viessmann Vitodens 100-W Combi Boiler is a proud holder of the coveted Which? Best Buy award, guaranteeing it one of the top spots when it comes to ranking the best small boilers. This wall-mounted boiler unit is compact and comes in a wide range of outputs, making it an ideal choice for any size of home with limited storage space.

Some of the top-selling qualities of the Viessmann Vitodens 100-W boiler range include class A energy efficiency, a 10-year comprehensive warranty, a backlit LCD touchscreen display, and a stainless heat exchanger. These boilers, especially the 2021 models, are also hydrogen-ready, meaning they can run on hydrogen fuel.

Alpha E-Tec Combi Boiler

Despite being a relatively new brand in the British boiler industry, Alpha has quickly established itself as one of the most reliable and affordable boiler brands. Thanks to its knockout performance and affordable prices, the Alpha E-Tec combi boiler is its best-selling boiler.

The Alpha E-Tec boiler has a stainless steel heat exchanger and a 7-year standard warranty. It also comes in two output ranges, 28kW and 38 kW, which can fit any property. This boiler is also compatible with leading third-party intelligent controls such as Hive and Nest.

Vaillant ecoFit pure Combi Boiler

Vaillant is another respected boiler manufacturer in the British boiler market. Their boilers are some of the most durable and reliable since they are fitted with stainless steel heat exchangers.

Vaillant ecoFit pure combi boiler is Vaillant’s smallest boiler unit in terms of size. This super-compact boiler can be squeezed into tiny spaces like the cupboard or behind the stairs. The boiler comes in three output ranges at 25kW, 30kW, and 35kW, making it a suitable choice for any small or medium-sized home.

Ideal Logic+ 24 Combi

The Ideal Logic+ 24 combi boiler is the most efficient and reliable boiler that Ideal has manufactured to date. In fact, the odds of your boiler ever breaking down is at an astounding low of 3%.  The boiler has a height of 700 mm and comes with a 2-year warranty that covers both labour and parts. Moreover, as the boiler is British-made, you won’t have trouble sourcing parts if anything goes wrong.

With a central heating output of 24kW, an efficiency rating of 94%, and a flow rate of 9.9 litres per minute, there is no doubt that the Ideal Logic+ 24 boiler is a perfect suit for a small home with limited storage space. The boiler also doesn’t make noise while operating and has been awarded the Quiet Mark Certification.

The boiler model has won several awards, including the Queen’s Award in 2013 and the Good Housekeeping Award in 2013 and 2017.

BAXI EcoBlue+ Combi Boiler

Although BAXI isn’t one of the premium boiler brands in the British boiler market, it is famous for its excellent customer service and lengthy warranties. The BAXI EcoBlue+ combi boiler is a compact boiler range with outputs of 24kW, 28kW, and 33kW. These boilers are powerful enough and can power any size of property ranging from a 1-bedroom bungalow to a 5-bedroom house. All the boilers in this range are highly reliable and come with a standard 5-year warranty which can be extended to 10 years.

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