Best Small Boiler for a Cupboard: Dimensions & More
Boilers are necessary for a house. Most homes in the UK have one installed to heat rooms and deliver hot water to bathrooms and taps. However, they are not always the best-looking or most space-saving appliances around.
Installing a compact boiler can help you save space in your home and make it look nicer. You could even merge them with your home style or decoration by, for instance, installing them within a cabinet in your kitchen or a different location. In this article, you will learn about the best small boilers for a cupboard!
Can you put a boiler in a cupboard?
Short answer: yes, you can. Many compact boilers easily fit in a standard cupboard. Whilst small, most are highly efficient units capable of running your radiators and supplying hot water to your shower(s) and taps.
If you are looking for one of these, you must ensure that the compact boiler dimensions are in the range of 700mm x 400mm x 300mm (height x width x depth). Typically, a boiler cupboard is bigger than that; however, you must consider clearance space for gas and water connections, flue pipes, and some room for engineers to service your boiler every year.
Size of the average cupboard
Kitchen cabinets come in different sizes, not to mention that you can build or buy a customised cupboard to hide a boiler.
In the UK, standard kitchen wall cupboards are likely 760mm or 900mm tall. According to the UK Metric Association, wall-mounted units are typically 300mm deep. Lastly, the width is usually a multiple of 100mm or 150mm (e.g. 400mm, 450mm, 500mm).
In any case, it is always best to measure your cupboard for precise measurements and avoid getting a boiler that doesn't fit in. You can also check the lists we have included below to look for the small boiler that fits your needs.
Additionally, asking a heating engineer for professional advice is always recommended. Otherwise, you could end up getting a boiler that fits your kitchen cupboard but fails to meet your home's heating and hot water demands.
Do you want to be 100% sure that you will get the correct boiler? We can help you find up to 3 quotes from Gas Safe and OFTEC registered engineers in your area to fit the best boiler for your home.
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Best compact boilers for a cupboard
In our research, we analysed different types of boilers from the top 5 boiler brands in the UK and renowned electric boiler manufacturers in the UK. Besides compactness, we focused on other 4 key aspects: available output sizes, efficiency, warranty, and price.
The output size indicates how powerful the boiler is rather than how big it is. Looking at the boiler’s output size you can estimate how well it can meet your house’s central heating and hot water demands. It is worth mentioning that combi boilers have 2 output sizes, one for central heating (CH) and one for domestic hot water (DHW). Find out ‘What size combi boiler do I need?’ in our comprehensive guide here.
Boiler efficiency is determined by how much fuel the boiler can turn into usable energy against how much fuel is wasted in the process. As we mentioned, efficiency is the secret to lower heating bills.
The next key aspect, the boiler warranty, refers to the period after installation where the manufacturer will send a heating engineer to your property to repair any faults. Generally, the longer the warranty period, the more reliable you can expect your boiler to be.
Lastly, by looking at the boiler price, you can have an idea of how much you would pay to get a new compact boiler.
- Baxi 800 Heat (regular boiler)
- Worcester Bosch Greenstar Ri (regular boiler)
- Viessmann Vitodens 100-W Heat Only (regular boiler)
- ELNUR Mattira MAS15 Electric System Boiler (electric boiler)
- Electric Heating Company Fusion Comet System Boiler (electric boiler)
- Worcester Bosch Greenstar CDi Compact (combi boiler)
- Worcester Bosch Greenstar i System (system boiler)
- Ideal Logic Max Combi (combi boiler)
- Ideal Logic Max System (system boiler)
- Baxi 800 Combi (combi boiler)
- Baxi 800 System (system boiler)
- Electric Heating Company Mercury Combi Boiler (electric boiler)
- Vaillant ecoFIT pure Combi (combi boiler)
- Viessmann Vitodens 050-W (combi boiler)
- Ferroli LEB System Electric Boiler (electric boiler)
Best small combi boiler
All in all, combi boilers are the most space-saving boilers because they don't require additional components such as hot water storage cylinders or feed tanks. If they are not at the top of the previous list, it is because we accounted just for the boilers' main unit. Thus, if saving space in your home is the priority, you should get one of these.
|Best Small Combi Boilers|
|Models||Dimensions (height x width x depth)||Maximum Output Ratings|
|Worcester Bosch Greenstar CDi Compact||690mm x 390mm x 280mm||CH: 24.3kW
DHW: 28kW, 32kW, 36kW
|Ideal Logic Max Combi||700mm x 395mm x 278mm||CH: 24.2kW
DHW: 24.2kW, 30.3kW, 35.3kW
|Baxi 800 Combi||700mm x 390mm x 285mm||CH: 21.2kW, 26.4kW
DHW: 25kW, 30kW, 36kW
|Vaillant ecoFIT pure Combi||700mm x 390mm x 295mm||CH: 19.1kW, 26.5KW
DHW: 25.2kW, 30kW, 35kW
|Viessmann Vitodens 050-W||700mm x 400mm x 300mm||CH: 19kW, 25kW
DHW: 25.4kW, 29.6kW
Worcester Bosch Greenstar CDi Compact
At 690mm x 390mm x 280mm, the Worcester Bosch Greenstar CDi Compact is the smallest combi boiler on our list. Despite being specifically designed to fit within a standard kitchen cupboard, it is a powerful heating unit capable of meeting the needs of different homes.
It might be helpful to know that Worcester Bosch is one of the most reliable boiler manufacturers on the market. Furthermore, the Greenstar CDi Compact model won the Which? Best Buy Gas and Oil Boilers award in September 2021.
- Available output sizes. Greenstar CDi Compact combi boilers come in 3 different DHW output ratings: 28kW, 32kW, and 36kW. The model with the lowest DHW output rating best suits homes with around 15 radiators and 1 bathroom, while the highest one works well for homes with 2 bathrooms or 1 bathroom plus an ensuite.
- Efficiency. This boiler has an efficiency rating of 94%. The entire Greenstar CDi Compact combi range is ErP A-rated for heat and domestic hot water. It means that this compact combi boiler can help you lower your energy bills. How much you can save will depend on the type of house and the difference between your old boiler and the new one concerning efficiency.
- Warranty. Worcester Bosch offers 10-year guarantees on the Greenstar CDi Compact range. Whilst you must fulfil all terms and conditions, you can rest assured that you have installed a boiler that will last a long time.
- Price. Including installation costs, VAT, and fittings, a Greenstar CDi Compact combi boiler price range goes from £1,800 to £2,670. However, this can vary considerably depending on factors such as the installer's rates and the city or region you live in.
Ideal Logic Max Combi
Measuring 700mm x 395mm x 278mm, the Ideal Logic Max is a compact combi boiler that will reliably heat your home. This small boiler is ready to run safely and efficiently on a 20% hydrogen blend with no technical adjustments, making it future-proof.
- Available output sizes. Ideal Logic Max combi boilers are also available in 3 different DHW output ratings: 24kW, 30kW, and 35kW. They can comfortably meet the central heating and hot water demands of houses with around 10 radiators and 1 bathroom. Naturally, the 35kW model can meet higher demands for hot water.
- Efficiency. Its 94% efficiency and ErP A rating for heat and hot water make the Logic Max combi a good choice to lower your annual energy bills. Per every £1 spent on heating, only 6p will be wasted.
- Warranty. Featuring a 10-year parts and labour warranty, this compact boiler will likely run for a long time without running into major problems.
- Price. Depending on the specific model, you can expect to pay between £1,768 and £2,456 for a Logic Max combi. This price range includes installation costs, VAT, and fittings.
Baxi 800 Combi
Baxi 800 series include combi boilers that can fit within a standard kitchen cupboard. Their dimensions are 700mm x 390mm x 285mm (height x width x depth). All Baxi 800 combi boilers are certified to run on a 20% hydrogen blend. They also come with an Adey Micro2 magnetic system filter to protect the heating system and boiler.
- Available output sizes. Baxi 800 combis include models with CH outputs of 21.2kW and 26.4kW, and DHW outputs of 25kW, 30kW, and 36kW. Generally, they are suitable for properties with low demand for central heating and hot water. However, the 36kW model (Baxi 836 combi) can comfortably meet higher demands.
- Efficiency. Boilers in the Baxi 800 range are 93% efficient, with an ErP A rating for heat and hot water.
- Warranty. Baxi offers a 10-year parts and labour warranty on this range. However, terms and conditions apply. One of the conditions states that your boiler must be serviced annually by a certified engineer.
- Price. All-inclusive (installation costs, VAT, and fittings), Baxi 800 combi boilers cost between £1,658 and £2,505.
Vaillant ecoFIT pure Combi
Boilers in the Vaillant ecoFIT pure combi series are Quiet Mark awarded. It means that they are among the quietest combi boilers on the market. Their dimensions in millimetres are 700 x 390 x 295, making these boilers compact enough to fit in a kitchen cupboard.
- Available output sizes. ecoFIT pure combi boilers are available in 3 DHW output sizes (25kW, 30kW, and 35kW). The least powerful boiler can meet the demand of smaller homes with 10-15 radiators and 1 bathroom, while the most powerful one can supply 1-2 bathrooms with hot water.
- Efficiency. These combi boilers are 94% efficient and ErP A-rated for heat and hot water. They can help you reduce your energy bills.
- Warranty. The standard warranty on ecoFIT pure combi models is 2 years. However, you can extend it to 7-10 years when you book a Vaillant Advance installer.
- Price. The estimated total price for ecoFIT pure combi boilers is £1,707 to £2,492. This includes installation costs, VAT, and fittings.
Viessmann Vitodens 050-W
At 700mm x 400mm x 300mm, the Vitodens 050-W series close or selection of best small gas combi boilers. Despite being cheap boilers, they do not compromise on quality.
- Available output sizes. Vitodens 050-W combi boilers come in 2 DHW output sizes: 25.4kW and 29.6kW. The first one is best suited for flats or small homes with 1 to 2 bedrooms, 1 bathroom, and up to ten radiators. The second model works well in houses with 3 to 4 bedrooms, 1 to 2 bathrooms, and up to 15 radiators.
- Efficiency. 92% of the fuel used by a Vitodens 050-W combi boiler is converted into heat. It also boasts an ErP A rating for heat and hot water.
- Warranty. Vitodens 050-W boilers come with a 3-year warranty as standard. There is the option to extend by a further 7 years if fitted by a Viessmann Trained Installer.
- Price. Just the boiler unit costs around £800. You will most likely pay an additional £800-£1300 for installation and fittings.
Best small system boiler
Moving to the list of best small system boilers, you first need to know that, whilst they can meet higher demands for hot water, system boilers include hot water storage cylinders. If saving the most space in your entire house is your main concern, then even the biggest combi boiler is a better option.
However, if your aim is saving space in your kitchen or tucking away your system boiler main unit, you can opt for one of the following models. In this case, we have included only 3 options as, all in all, they are not as compact as gas combi or electric combi boilers.
|Best Small System Boilers|
|Models||Dimensions (height x width x depth)||Maximum Output Ratings|
|Worcester Bosch Greenstar i System (27kW & 30kW models)||690mm x 390mm x 280mm||CH: 27kW, 30kW|
|Ideal Logic Max System||700mm x 395mm x 278mm||CH:15kW, 18kW, 24.2kW, 30.3kW|
|Baxi 800 System||700mm x 390mm x 285mm||CH: 19.4kW, 25.8kW|
Worcester Bosch Greenstar i System
The Worcester Bosch Greenstar i is the smallest system boiler on our list of the best compact boilers. The main unit fits comfortably within a cupboard. Its measurements are 690mm x 390mm x 280mm.
However, these dimensions apply to the 27kW and 30kW models, as less powerful units in the range are bigger in physical size.
According to the manufacturer, Greenstar i system boilers can be used with Greenskies solar panels for energy and cost savings.
- Available output sizes. The Greenstar i system range includes boilers with CH output sizes from 9kW to 30kW. However, the 27kW and 30kW models are the most compact ones. These two are powerful appliances capable of running around 20 radiators.
- Efficiency. These boilers are 92% efficient and ErP A-rated for heat.
- Warranty. Worcester Bosch offers a 10-year guarantee on the Greenstar i range. Terms and conditions apply.
- Price. Including VAT, installation, and fittings, these two boilers in the Greenstar i system range cost £1,867 to £2,414.
Ideal Logic Max System
Like its combi 'cousin', the Ideal Logic Max system boiler dimensions are 700mm x 395mm x 278mm. It is also ready to run on a 20% hydrogen blend.
- Available output sizes. Ideal Logic Max system boilers are available in 4 CH output ratings: 15kW, 18kW, 24kW, and 30kW. Thus, you have enough options to choose from to meet the needs of small to large houses.
- Efficiency. Whilst all 4 models are ErP A-rated, only the Logic Max S24 (24kW) boasts a seasonal efficiency of 94%. The other three are also highly-efficient boilers, but they peak at 93%.
- Warranty. These boilers are covered by a 10-year parts and labour warranty; however, it is subject to terms & conditions.
- Price. Depending on the specific model, the typical total cost of a Logic Max system boiler ranges from £1,770 to £2,384.
Baxi 800 System
Baxi 800 system boilers also share many characteristics with their combi counterparts. For instance, they both have the same dimensions (700mm x 390mm x 285mm). They are also certified to run on a 20% hydrogen blend and come with an Adey Micro2 magnetic system filter.
- Available output sizes. The Baxi 800 system series includes two models: Baxi 818 System and Baxi 824 System. With CH output ratings of 19.4kW and 25.8kW, respectively, they are suitable for medium-sized homes and also larger homes with 2+ bathrooms.
- Efficiency. Boilers in the Baxi 800 system range are also 93% efficient, with an ErP A rating for heat.
- Warranty. These boilers come with a 10-year parts and labour warranty, subject to terms and conditions.
- Price. Baxi 800 system boilers cost between £1,713 and £2,257, all-inclusive.
Best small heat-only boiler
Just as in the system boilers section, we first need to point out that regular boilers are the most space-consuming boilers you can install. In addition to hot water storage cylinders, they need water tanks in the loft. However, regular boiler main units can be very compact, so compact that they top our list of the best compact boilers for a cupboard.
|Best Small Regular Boilers|
|Models||Dimensions (height x width x depth)||Maximum Output Ratings|
|Baxi 800 Heat||625mm x 370mm x 270mm||CH: 16kW, 25kW, 30kW|
|Worcester Bosch Greenstar Ri||600mm x 390mm x 270mm||CH: 12kW, 15kW, 18kW, 21kW, 24kW, 27kW, 30kW|
|Viessmann Vitodens 100-W Heat Only||600mm x 375mm x 285mm||CH: 11kW, 16kW, 19kW, 25kW, 32kW|
Baxi 800 Heat
At 625mm x 370mm x 270mm, the Baxi 800 Heat Only boiler is the smallest heat-only boiler in our selection. Considering just the main unit, it is the most compact boiler for a cupboard. Like combi and system models in the Baxi 800 range, this brand's regular boilers come with an Adey Micro2 magnetic system filter and are certified to run on a 20% hydrogen blend.
- Available output sizes. The Baxi 800 Heat Only series includes three models: Baxi 816 Heat, Baxi 825 Heat, and Baxi 830 Heat. Depending on the model, they can cover the demand of medium-sized houses with up to 15 radiators to larger homes with around 20 radiators.
- Efficiency. Baxi 800 Heat Only boilers are also 93% efficient, with an ErP A rating for heat./li>
- Warranty. With a 10-year parts and labour warranty, you can rest assured that a Baxi 800 Heat Only boiler will not run into major problems for a long time.
- Price. Their typical all-inclusive cost ranges from £1,587 to £2,244. The least powerful model is the cheapest one in the range.
Worcester Bosch Greenstar Ri
Excluding storage cylinders and feed tanks, a Greenstar Ri regular boiler main unit's measurements are 600mm x 390mm x 270mm. This boiler fits in a kitchen cupboard, with plenty of room to spare.
According to the manufacturer, all their small gas boilers can run on a 20% hydrogen blend.
- Available output sizes. The Greenstar Ri range includes regular boilers with CH output sizes of 12kW, 15kW, 18kW, 21kW, 24kW, 27kW, and 30kW. As you can see, you have several options to choose from to meet your home needs regardless of size.
- Efficiency. The 27kW and 30kW are 93% efficient, while the other five models are 92%. All models in the Greenstar Ri range are ErP A-rated for heat.
- Warranty. Worcester Bosch offers a 10-year guarantee on Greenstar Ri boilers when installed by a Worcester Accredited Installer. Additional terms and conditions may apply.
- Price. Including VAT, installation, and fittings, these boilers cost between £1,614 and £2,380. The most powerful ones are, of course, the most expensive too.
Viessmann Vitodens 100-W Heat Only
The Viessmann Vitodens 100-W Heat Only boiler is a wall-mounted condensing boiler compact enough to fit in a standard kitchen cupboard. Its main unit's measurements are 600mm x 375mm x 285mm.
The manufacturer offers an upgrade option to make the boiler operate in weather compensation mode. This feature can help you achieve gas savings of up to 12% in the process.
- Available output sizes. The Vitodens 100-W Heat Only range also offers several options to meet the demands of almost any type of house. Their available CH output ratings go from 11kW to 32kW.
- Efficiency. All boilers in the Vitodens 100-W Heat Only range are 92% efficient and ErP A-rated for heat.
- Warranty. These models come with a 5-year warranty as standard. It can be extended to 12 years if installed by a Viessmann Trained Installer.
- Price. Currently, some Viessmann partners' web pages show Vitodens 100-W Heat Only prices ranging from £1,099 to £1,607 (Inc. VAT). However, it is subject to availability. They also mention that the Recommended Retail Price is much higher (£2,199.60 to £3,214.80)
Best small electric boiler
Electric boilers are also a good option to save space in your kitchen. Like compact gas boilers, you can also tuck away a small electric boiler in a cupboard. Some electric boilers need hot water storage cylinders, like gas system boilers. Other models don't, making them all-around space savers, like combi gas boilers.
Our selection below focuses on electric boiler main units' dimensions.
|Best Small Electric Boilers|
|Models||Dimensions (height x width x depth)||Maximum Heating Power|
|ELNUR Mattira MAS15 Electric System Boiler||760mm x 350mm x 265mm||Modulates from 3kW to 15kW|
|Electric Heating Company Fusion Comet System Boiler||710mm x 418mm x 251mm||6kW, 9kW, 12kW, 14.4kW|
|Electric Heating Company Mercury Combi Boiler||690mm x 451mm x 258mm||12kW, 14.4kW, 19kW, 26kW|
|Ferroli LEB System Electric Boiler||740mm x 440mm x 265mm||6kW, 7.5kW, 9kW, 12kW|
ELNUR Mattira MAS15 Electric System Boiler
The ELNUR Mattira MAS15 is a digital modulating, heating only electric boiler. Its main unit measurements are 760mm x 350mm x 265mm, making it the smallest electric boiler on our list. However, it needs a storage cylinder to supply hot water to your taps, so you will need extra space to fit all its components.
According to the manufacturer, this electric boiler is compatible with underfloor heating.
- Available heating power. The Mattira MAS15 Electric System Boiler features a Smart Electronic Modulating System that allows you to control the heater. It can modulate from 3kW to 15kW, meaning that you can adjust this boiler to suit small homes with 2 radiators to medium-sized homes with around 10 radiators.
- Efficiency. This boiler's efficiency varies depending on the power output it is operating. At 3kW, it is 100% efficient. However, at 15kW, efficiency decreases to 36,4%. The Mattira MAS15 has an ErP D-rating*.
- Warranty. The internal components are warranted against faulty materials and manufacture defects for 5 years from the date of purchase. Terms and conditions apply.
- Price. Including VAT, installation costs and fittings, this boiler costs between £2,000 – £2,500.
EHC Fusion Comet System Boiler
Boilers in the Fusion Comet System range by the Electric Heating Company (EHC) are a good choice for wet central heating and underfloor heating systems. Their main units (710mm x 418mm x 251mm) comfortably fit in a cupboard. Though, they also need hot water storage cylinders.
- Available heating power. Fusion Comet System boilers are available in 4 heating power outputs: 6kW, 9kW, 12kW, and 14.4kW. Depending on the output, they can meet the needs of houses with up to 4 radiators to medium-sized homes with around 10 radiators.
- Efficiency. All 4 models are 100% efficient and ErP D-rated*.
- Warranty. Fusion Comet System boilers are covered by a 5-year warranty. You must comply with the terms and conditions to keep the warranty valid throughout the whole period.
- Price. These boilers' typical total price ranges from £2,146 to £2,762.
EHC Mercury Combi Boiler
Mercury Combi electric boilers are a compact solution for heating and hot water. Their 690mm x 451mm x 258mm make them ideal for installation within a cupboard.
They don't require a cylinder to supply hot water to your bathrooms and taps; nevertheless, you can use them with a hot water cylinder to meet higher demands. Mercury combi boilers also feature weather compensation systems.
- Available heating power. Mercury Combi boilers come in 4 heating power outputs: 12kW, 14.4kW, 19kW, and 26kW. The first two are single-phase models, so they are recommended for small properties that have a shower but without a bath. The other two are three-phase boilers capable of filling a bath in a suitable timescale.
- Efficiency. All four models are 100% efficient. They boast an ErP A- rating for hot water but are ErP D-rated* for heat.
- Warranty. Like other electric boilers by the EHC, Mercury Combi boilers are covered by a 5-year warranty.
- Price. The manufacturer's website currently shows Mercury combis' prices ranging from £1,394.82 to £1,559.02. The three-phase models are at the most expensive end.
Ferroli LEB System Electric Boiler
At 740mm x 440mm x 265mm, the Ferroli LEB System Electric Boiler is a compact boiler that can fit inside a cupboard. Nevertheless, it needs an external storage cylinder to supply domestic hot water. It is compatible with underfloor heating.
- Available heating power. These boilers are available in four heating power outputs: 6kW, 7.5kW, 9kW (single-phase models), and 12kW (three-phase model). Depending on the model, these boilers can meet the demands of small homes with 4 to 8 radiators. In all cases, they are best suited for houses with only 1 bathroom.
- Efficiency. Ferroli LEB System Electric boilers are 99.5% efficient and ErP D-rated*.
- Warranty. Like other electric boilers by the EHC, Mercury Combi boilers are covered by a 5-year warranty.
- Price. Their typical total cost ranges from £1,400 to £2,115.
* While electric boilers boast 99-100% efficiency ratings, many of them have an ErP D-rating. This is rather low compared to the A-rating awarded to gas boilers. The reason is that most electricity is generated by burning fossil fuels. Therefore, it is considered carbon-intensive and not very efficient.
However, renewable energy generation has increased considerably in recent years. Hence, the ErP rating given to electric boilers will likely improve in the near future.
After going through our list, you surely have a better idea of which compact boiler is best for your home. Are any of these combi, system, regular or electric boilers a match? You can follow the links in the descriptions (under Maximum Output Ratings / Available Heating Power) to get FREE quotes for the boiler you like the most.
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What is the size of the smallest boiler?
Considering only the main unit, the smallest boilers on our list of best compact boilers for a cupboard are those in the Baxi 800 Heat series. Their dimensions are 625mm x 370mm x 270mm (height x width x depth).
However, as regular boilers, they need a storage cylinder and a feed tank to supply your bathroom(s) with hot water. If you want to save as much space as possible all over your home, then the Worcester Bosch Greenstar CDi Compact combi boiler is better. Its dimensions are 690mm x 390mm x 280mm.
What is the smallest combi boiler in the UK?
The Worcester Bosch Greenstar CDi Compact combi boiler is the smallest combi boiler on our list of best compact boilers for a cupboard (unit dimensions: 690mm x 390mm x 280mm).
What is the smallest system boiler?
The Worcester Bosch Greenstar i System boiler is the smallest system boiler on our list of best compact boilers for a cupboard (Unit dimensions: 690mm x 390mm x 280mm).
What is the smallest heat-only boiler?
Baxi 800 Heat boilers are the smallest heat-only boilers on our list of best compact boilers for a cupboard (Unit dimensions: 625mm x 370mm x 270mm).
Can you put a Worcester Bosch boiler in a cupboard?
You can put a Worcester Bosch boiler in a cupboard. This brand includes ranges of highly-efficient and compact combi, system, and regular gas boilers. Worcester Bosch manufactures some of the best compact boilers for a cupboard available in the UK.