Best Compact (Small) Combi Boilers for 2024

If you're looking to install a new combi boiler into a tight space such as a kitchen cupboard or small utility room, you'll need a model with smaller dimensions.

After carrying out extensive research into the best (physically) small-sized combi boiler, system and regular boilers and checking out reviews from both customers and engineers, we have compiled a list of the top compact boiler models on the market. So let's get into it!

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Best Compact Small Combi Boilers

Combi boilers are the most compact type of boiler as they combine both a water heater and central heating into a single unit, meaning there's no need for additional hot and cold water tanks that take up lots of space, making them ideal for fitting in kitchen cupboards.

Here are our top compact combi boilers and why we love them so much:

Worcester Bosch Greenstar CDi Compact

Dimensions: W 390mm, D 280mm, H 680mm

The Worcester Bosch Greenstar CDi Compact is a bite-size combi boiler that was specifically designed to fit within a standard kitchen cupboard. Despite its compact size, this combi boiler still delivers incredible heating and hot water, with various outputs available to suit different homes.

Winner of the Which? Best Buy Gas and Oil Boilers award in September 2021 and produced by one of the most reliable boiler manufacturers on the market, you can count on this boiler to deliver effective and efficient heating for a long time, keeping your home warm with much lower running costs.

Worcester Bosch Greenstar CDi Compact Output Sizes

When talking about combi boiler size, we usually refer to the power output in kW. Generally, the larger your home and the higher demand for heating and hot water, the higher the boiler power output you will require.

The Greenstar CDi Compact is available in the following power output sizes:

Worcester Bosch Greenstar CDi Compact Efficiency

One of this model's key features is its efficiency. The entire Worcester Bosch Greenstar CDi Compact Combi range is ErP A-rated thanks to its impressive 91% efficiency.

By replacing an old, inefficient combi boiler with this new combi, you could save up to £380 a year on your energy bills.

Worcester Bosch Greenstar CDi Compact Prices

If you purchase a Worcester Bosch Greenstar CDi through iHeat, our fixed price includes the new combi boiler and complete installation from our Gas Safe engineers, delivering the full package.

Prices for the Worcester Bosch Greenstar Compact range plus installation begin at £2,085 and are available with several finance options to help you spread the cost.

Although there are cheaper options on the market, the Worcester Bosch price tag is high for a reason.

Why buy this boiler?

• Firstly, they offer 10-year guarantees (not warranties). Guarantees typically cover the whole product, and Worcester Bosch won't charge you for a guarantee call-out visit providing that your boiler is serviced annually.

• Winner of multiple Which? Best Buy awards

• High TrustPilot ratings

• Huge brand name thanks to reliability

• Made in the UK

Ideal Logic + Combi

Dimensions: W 395mm, D 279mm, H 700mm

The Ideal Logic Plus Combi boiler is a fantastic little appliance, scoring highly on efficiency and delivering speedy heating and hot water, all whilst being able to tuck away neatly into a kitchen cupboard.

The boiler is supported by the Queen’s Award for Enterprise 2013 and the Good Housekeeping Reader Recommended Status in 2013 and 2017, so you can be sure it’s a good choice!

Ideal Logic + Combi Output Sizes

The Ideal Logic+ is available in the following power output sizes:

Ideal Logic + Efficiency

The Ideal Logic + isn’t quite as efficient as the Worcester Bosch CDi Compact, however, it still offers a fantastic 90% energy efficiency, delivering more cost-effective heating and hot water, helping to keep your central heating bills low.

Ideal Logic + Combi Prices

If you purchase an Ideal Logic Plus through iHeat, you can get a fixed price for the combi boiler and installation by our Gas Safe installers. Prices for the Ideal Logic + Combi boiler range plus installation begin at £1,895 and are available with several finance options to help you spread the cost.

Included in our prices is a fantastic 10-year warranty that we offer exclusively with all our combi boilers here at iHeat.

Viessmann Vitodens 100-W

Dimensions: W 400mm, D 350mm, H 700mm

Efficient, compact, quiet and affordable, the Viessmann Vitodens 100-W combi boiler is the most popular solution available at iHeat. Reviewed as a Which? Best Buy in 2019, the Vitodens 100-W features innovative technology and services combined with reliability and longevity.

This combi helps you to optimise your heating and save on energy costs and can all be done from inside your kitchen cupboard.

Viessmann Vitodens 100-W Output Sizes

The Viessmann Vitodens 100-W is available in the following power output sizes:

Viessmann Vitodens 100-W Efficiency

Up to 94% of the fuel used by the Viessmann Vitodens 100-W is converted into heat, making it an incredibly efficient boiler. According to Viessmann, this could help you to save up to 40% off your energy bills when replacing an old inefficient model.

Viessmann Vitodens 100-W Prices

If you purchase a Viessmann Vitodens 100-W combi boiler through iHeat, you can get a fixed price for both the boiler itself plus installation by our Gas Safe installers.

Prices for the Vitodens 100-W range plus installation start at £2,395 and are available with several finance options to help you spread the cost.

Although this boiler is on the slightly pricier side, you can be sure to get your money’s worth.

Viessmann recently updated the 100-W for 2021, featuring all-new innovative technology and services combined with reliability and longevity ready for smart technology, helping you optimise your heating and save on energy costs.

Viessmann Vitodens 050-W

Dimensions: W 400mm, D 350mm, H 707mm

With compact dimensions, low weight and quiet operation, the attractively priced Vitodens 050-W combi boiler is a low-cost gas combi boiler that will integrate effortlessly into any living space and does not compromise on quality; making it ideal for both new build homes and modernisations.

The Vitodens 050-W 29 kW Combi boiler was also reviewed as a Which? Best Buy in 2019.

Viessmann Vitodens 050-W Output Sizes

The Viessmann Vitodens 050-W is available in the following power output sizes:

Viessmann Vitodens 050-W Efficiency

Like the 100-W, 94% of the fuel used by the Viessmann Vitodens 050-W is converted into heat, so this model is equally as efficient, with an A rating, helping you to cut hundreds off your heating bill each year.

Viessmann Vitodens 050-W Prices

If you purchase a Viessmann Vitodens 050-W through iHeat, you can get a fixed price for both the combi boiler itself plus installation by our Gas Safe installers.

Prices for the Vitodens 050-W range plus installation start at £2,055 and are available with several finance options to help you spread the cost to make it more affordable.

At nearly £200 cheaper than its 100-W counter model, you may wonder what separates them.

One of the key differences between the two is that the Vitodens 050-W has a smaller depth than the 100-W, being just 350mm deep, which is 50mm shallower than the 100-W, making it a more suitable choice for those who are tight for space.

The depth of the combi boiler is particularly important because there needs to be an open space of at least 60mm for an engineer to access it during its annual service properly.

Another difference is the size of the LED screen on the front of the unit. The 100-W does have a much larger screen, making it easier to see and operate; however, for many, this isn’t a great enough difference to justify paying for the more expensive model.

Alpha E-Tec

Dimensions: W 440mm, D 275mm, H 712mm

The entire E-Tec range is Alpha’s smallest yet, designed to fit into a unit with small dimensions. Compactness allows an easy fit in a standard kitchen cupboard, and annual servicing is made easy with front access.

Alpha E-Tec Output Sizes

The Alpha E-Tec combi boiler is available in the following power output sizes:

Alpha E-Tec W Efficiency

Much like the rest of this list, the Alpha E-Tec has an incredibly high energy efficient rating of 89%, so you can rest easy knowing your energy bills won’t be any higher than necessary.

Alpha E-Tec 050-W Prices

The Alpha E-Tec combi boiler is our most affordable boiler at iHeat, but don’t expect it to compromise quality.

It might not be the flashiest of boilers, but it’s certainly robust and reliable and sure to last you a long time with fantastic heating results.

If you purchase an Alpha E-Tec combi boiler through iHeat, you will pay a fixed price for both the boiler itself and installation by one of our Gas Safe installers.

Prices for the Alpha E-Tec range plus installation start at £1,675 and are available with several finance options to help you spread the cost.

iHeat New Boiler Costs

Boilers can be a daunting purchase for many people as they’re an appliance with a lot of responsibility, providing heat for you and your family is something you want to get right. Boilers aren’t exactly a quickly disposable item either, potentially lasting you a decade.

Boiler costs can be split into two segments: the first is the actual boiler itself (unit price), and the second is the cost of the boiler being installed (set up) in your property by an expert engineer. 

Here at iHeat, we want to remove all of this undue stress and make the decision making process of upgrading to a new central heating system, as easy as possible.

Boiler costs can vary depending on a number of factors including their brand, model, fuel, output, warranty, labour and installation type. Typically a new boiler will cost between £1,845 and £3,500, below is a list of average boiler installations offered by iHeat (guide only).