When space is limited, compact boilers are a smart heating solution. They fit into tight areas like kitchen cupboards and provide high efficiency (90%-94%) while eliminating the need for bulky water tanks. These boilers are ideal for small homes, apartments, or properties with limited room. Below are the top 5 compact boilers, highlighting their key features:
- Intergas Compact ECO RF: Slim design, 93%-94% efficiency, and easy installation. Prices range from $2,150 to $2,800 (including installation).
- Glow-worm Compact Combi: Small size, 91%-93.2% efficiency, and lightweight. Suitable for homes with one bathroom.
- Worcester Bosch Greenstar CDi Compact: 94% efficiency, high flow rate, and frost protection. Costs $2,200-$2,800 with installation.
- Viessmann Vitodens 050-W: 98% efficiency, hydrogen-ready, and quiet operation. Installation costs range from $2,800 to $3,350.
- Ideal Logic Plus: 94% efficiency, 7-10 year warranty, and compact design. Great for small homes or apartments.
Quick Comparison
| Model | Dimensions (H x W x D) | Efficiency | Max Flow Rate | Price Range (Installed) |
|---|---|---|---|---|
| Intergas Compact ECO RF | 28" x 17.7" x 9.4" | 93%-94% | 12.7 L/min | $2,150-$2,800 |
| Glow-worm Compact Combi | 24.6" x 15.7" x 10.6" | 91%-93.2% | 11.5 L/min | $2,000-$2,500 |
| Worcester Bosch Greenstar CDi | 27.2" x 15.4" x 11" | 94% | 12.9 L/min | $2,200-$2,800 |
| Viessmann Vitodens 050-W | 27.6" x 15.7" x 11.8" | 98% | 14.3 L/min | $2,800-$3,350 |
| Ideal Logic Plus | 27.6" x 15.6" x 11" | 94% | 14.5 L/min | $2,500-$3,000 |
These boilers combine space-saving designs with energy efficiency, making them perfect for small spaces. Professional boiler installation by a Gas Safe registered engineer is recommended to ensure safety and optimal performance. Regular boiler maintenance is also essential to keep these compact units running efficiently.
Compact Boiler Comparison: Top 5 Models by Dimensions, Efficiency, and Price
1. Intergas Compact ECO RF
Compact Dimensions
When space is tight, the Intergas Compact ECO RF shines with its small yet efficient design. Measuring just 28 inches high (710 mm), 17.7 inches wide (450 mm), and 9.4 inches deep (240 mm), this boiler is compact enough to fit inside standard kitchen cupboards. Its wall-mounted design eliminates the need for bulky water tanks or cylinders, making it perfect for smaller homes. As Intergas Heating explains:
"This boiler is ideal for smaller homes where space is limited, as it does not require an external water tank or cylinder."
The 30 kW model is priced at around $1,500, with installation costs ranging between $650 and $1,300. This brings the total cost to approximately $2,150–$2,800.
Energy Efficiency
With an efficiency range of 93%–94%, the Intergas Compact ECO RF is designed to save energy and reduce costs. It boasts an ErP A-rating for both heating and hot water. A key feature is its 2-in-1 bitermic heat exchanger, which heats mains water directly and allows the boiler to condense continuously. This design reduces energy waste and ensures consistent performance. The boiler also operates with only 12 components and 4 moving parts, which enhances reliability and keeps standby power usage below 2.0 watts. For even better energy management, it pairs seamlessly with Honeywell wireless thermostats.
Ease of Installation
Installers often praise the Intergas Compact ECO RF for its user-friendly setup. Pre-configured piping and a flylead make wiring straightforward, while the built-in RF technology enables remote performance monitoring when paired with the optional Intergas LAN Gateway. This reduces the need for frequent on-site inspections. Additionally, the boiler offers flexible maintenance scheduling, requiring servicing after 1,700 hours of use instead of adhering to a strict annual timeline.
You can also compare Navien boiler prices and installation costs to see how they stack up against the Intergas model. Next, take a look at another compact boiler that combines efficiency with smart design.
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2. Glow-worm Compact Combi
Compact Dimensions
The Glow-worm Compact Combi is designed with space-saving in mind. Measuring just 24.6 inches high (626 mm), 15.7 inches wide (400 mm), and 10.6 inches deep (270 mm), it can easily fit inside standard kitchen cupboards. This shallow depth is a big plus since most kitchen wall cupboards are around 11.8 inches (300 mm) deep. Factoring in hinges, back panels, and pipe connections, usable space can be tight, but this boiler’s size works perfectly within those limits. Both models in this range share the same dimensions, making them a practical option for compact spaces.
Energy Efficiency
Despite its small size, the performance of the Glow-worm Compact Combi is impressive. The 24 kW model achieves 91% efficiency, while the 28 kW version reaches 93.2%. Both models boast an ErP A rating for heating and hot water. When paired with smart controls like MiSet or MiGo Select, the boiler adjusts its output to meet demand, ensuring energy isn’t wasted. The MiGo Link internet gateway adds weather compensation, allowing the boiler to adapt its operation based on outdoor temperatures, which further improves efficiency. These features not only enhance comfort but also help lower utility bills.
Suitability for Small Spaces
Weighing less than Glow-worm’s other boilers, this model is perfectly suited for installations where weight is a concern. Its quiet operation makes it a great choice for living spaces like kitchens. The 24 kW model provides 9.9 liters of hot water per minute, while the 28 kW version delivers 11.5 liters per minute, making it ideal for smaller homes, apartments, or bungalows with one bathroom. The compact design ensures it won’t dominate your space, even if installed in a visible area.
Ease of Installation
Thanks to its lightweight design, the Glow-worm Compact Combi is easy for technicians to handle and install. It also comes with a 5-year guarantee, offering reliable performance without the need for additional warranty costs.
Next, we’ll look at how these features combine to make this boiler a practical and efficient choice for modern homes.
3. Worcester Bosch Greenstar CDi Compact
Compact Dimensions
The Worcester Bosch Greenstar CDi Compact is designed with small spaces in mind. It measures 27.2 inches in height, 15.4 inches in width, and only 11 inches in depth. That’s a full 2 inches slimmer than standard boilers, making it a perfect fit for most standard kitchen cupboards. Gas Safe Registered Engineer Patrick Garner humorously describes it:
"The Worcester Bosch Greenstar CDi compact is a compact yet powerful unit which’ll slip in to any slinky kitchen cupboard, with room to spare. It’s the Danny Devito of boilers."
Just remember to leave at least 24 inches of clearance in front of the unit for easy access during annual servicing.
Energy Efficiency
This boiler boasts a 94% efficiency rating during normal operation, which can climb up to 99.5% when running at lower capacity. Such high efficiency means less fuel waste and noticeable savings on energy bills. If you’re replacing an outdated G-rated boiler, those savings can be substantial. As Patrick Garner puts it:
"If you upgrade from an old G-rated boiler, you can potentially save hundreds of pounds a year on heating costs. That’s right, hundreds of pounds. Not tens of pounds."
It’s also equipped with frost protection, activating the pump when temperatures drop below 46°F (8°C). Additionally, the CondenseSure siphon prevents freezing down to 5°F (-15°C) for up to 48 hours, ensuring reliable operation in colder climates.
Suitability for Small Spaces
The Greenstar CDi Compact is available in 28 kW, 32 kW, and 36 kW models, all offering the same compact design. Depending on the model, it provides a flow rate between 10 and 12.9 liters per minute (roughly 2.6 to 3.4 gallons per minute). This makes it an excellent choice for homes with one bathroom and up to 15 radiators. As a combi boiler, it eliminates the need for external water tanks or cylinders, saving even more space in smaller homes.
Ease of Installation
Its wall-mounted design and slim profile simplify installation, especially in tight spaces. Certified technicians will appreciate its user-friendly features, including an easy-to-read display with clear temperature readings and a low-energy pump to reduce power consumption. Worcester Bosch provides up to a 10-year warranty when the boiler is installed by an accredited professional.
The brand’s reputation speaks for itself – it has received the Which? Best Buy Award for 10 years running and boasts a 4.7/5 rating from over 27,000 reviews. Installation costs typically range from $600 to $1,200, with total project expenses (including the boiler and materials) falling between $2,200 and $2,800. For expert installation and maintenance, Eco Temp HVAC in the Chicagoland area is a reliable option (https://ecotemphvac.com).
4. Viessmann Vitodens 050-W
Compact Dimensions
The Viessmann Vitodens 050-W is designed with space-saving in mind, measuring about 27.6 inches tall, 15.7 inches wide, and 11.8 inches deep. Its compact size means it can easily fit inside a standard kitchen cupboard, making it a perfect choice for apartments or smaller homes. Thanks to its front-access design, all connections are within easy reach, so there’s no need for side clearance during servicing. This makes it ideal for tight spaces. Plus, it operates quietly, meaning it can be installed in living areas without causing any disturbances.
Energy Efficiency
This model doesn’t just save space – it’s also highly efficient, boasting a seasonal efficiency rating of 98%. Its standout performance comes from the combination of a stainless steel Inox-Radial heat exchanger, a MatriX-Plus burner, and a Lambda Pro combustion controller. Gas Safe Registered Engineer Patrick Garner highlights the heat exchanger’s reliability:
"The stainless steel exchanger of the Vitodens 050-W is sturdy and dependable like a thick white loaf or your first Nokia."
With a high modulation range of 1:8, the boiler adjusts its output efficiently to save energy. It’s also "H2 ready", meaning it can operate with a 20% hydrogen mix, adding a layer of future-proofing to its design.
Suitability for Small Spaces
Available in 25 kW, 30 kW, and 35 kW models, the Vitodens 050-W delivers hot water flow rates between 12.2 and 14.3 liters per minute (about 3.2 to 3.8 gallons per minute). As a combination boiler, it eliminates the need for separate water tanks, making it a smart choice for homes with limited space. For even greater convenience and energy savings, it can connect with smart thermostats like tado or Google Nest. These integrate with the ViCare app, allowing for remote control and weather-compensated heating.
Ease of Installation
The boiler’s low height and front-facing components make installation straightforward, especially when replacing older, bulkier units. It’s compatible with both natural gas and LPG, adding flexibility. A shock arrestor is included as standard equipment. In the U.S., installation costs typically range from $2,800 to $3,350, depending on the model.
Viessmann UK has earned a solid reputation, with an average Trustpilot rating of 4.3 out of 5 stars from over 6,800 reviews as of July 2024. Additionally, the Vitodens 050-W received the Which? Best Buy award from 2017 to 2020. This boiler combines efficient performance with a compact design, making it a reliable choice for modern homes.
5. Ideal Logic Plus
Compact Dimensions
The Ideal Logic Plus Combi boiler is designed with space-saving in mind. Measuring 27.6 inches tall, 15.6 inches wide, and 11 inches deep (279 mm), it fits perfectly into standard kitchen wall cabinets, leaving enough room for pipe connections, isolation valves, and cabinet hinges. Weighing just 64.4 pounds (29.2 kg), it’s easy to install, even in tight or elevated spaces. With output options of 24 kW, 30 kW, and 35 kW, it offers reliable heating while preserving precious space.
Energy Efficiency
With a seasonal space heating efficiency of 94% and an "A" rating for both space and water heating, the Ideal Logic Plus is designed for energy-conscious users. The boiler’s modulating operation adjusts output as low as 4.8 kW, ensuring it only consumes the fuel necessary. It’s also environmentally friendly, meeting NOx Class 6 standards for low nitrogen oxide emissions. Quiet operation is another bonus, with sound levels of 44 dB for the 35 kW model and 48 dB for the 24 kW version. Backed by an "Excellent" 4.8-star Trustpilot rating from over 70,472 reviews (as of April 2026) and recognition from the Energy Saving Trust, this boiler delivers both efficiency and performance.
Suitability for Small Spaces
Thanks to its slim profile, the Logic Plus is a great choice for compact living. As a combination boiler, it eliminates the need for separate water tanks, making it ideal for apartments and smaller homes. The 24 kW model provides a hot water flow rate of 9.9 liters per minute (about 2.6 gallons per minute), while the 35 kW version offers 14.5 liters per minute (roughly 3.8 gallons per minute) at a 35°C temperature rise. For small flats or bungalows, the 24 kW model is often sufficient, while medium-sized homes with higher water demands might prefer the 30 kW or 35 kW options. Built-in frost protection adds to its versatility, particularly for less insulated spaces.
Ease of Installation
The Logic Plus is designed with user-friendly installation features, including preformed copper tails, concealed pipe connections, a universal condensate connection, and flexible flueing options. To ensure it fits, measure your kitchen cupboard depth, accounting for hinges, back panels, and pipework – its 11-inch depth is compact but requires precise planning. The boiler comes with a 7-year parts and labor warranty and a 10-year heat exchanger warranty, provided it’s registered within 30 days and serviced annually by a Gas Safe registered engineer. While the 24 kW and 30 kW models can be converted for LPG use, the 35 kW version cannot, so choose accordingly.
Worcester Bosch CDI Compact Combi Boiler Review
Boiler Comparison Table
Picking the right compact boiler means juggling a few important factors – size, power, hot water flow rate, and efficiency. To make things easier, here’s a side-by-side comparison of five popular models:
| Model | Dimensions (H x W x D) | Output Options | Max Flow Rate | Efficiency Rating |
|---|---|---|---|---|
| Intergas Compact ECO RF | 27.6" x 15.4" x 11" (700 x 390 x 280 mm) | 24, 28, 30 kW | 12.7 L/min (3.4 gal/min) | 94% (A-rated) |
| Glow-worm Compact Combi | 27.6" x 16.5" x 11.8" (700 x 420 x 300 mm) | 25, 30 kW | 12.5 L/min (3.3 gal/min) | 93% (A-rated) |
| Worcester Bosch Greenstar CDi Compact | 26.8" x 15.4" x 11" (680 x 390 x 280 mm) | 28, 32, 36 kW | 14.7 L/min (3.9 gal/min) | 94% (A-rated) |
| Viessmann Vitodens 050-W | 27.8" x 15.7" x 13.8" (707 x 400 x 350 mm) | 25, 30, 35 kW | 14.3 L/min (3.8 gal/min) | 94% (A-rated) |
| Ideal Logic Plus | 27.6" x 15.6" x 11" (700 x 395 x 279 mm) | 24, 30, 35 kW | 14.7 L/min (3.9 gal/min) | 94% (A-rated) |
This table highlights the essential specs to help you find a boiler that fits both your space and your heating needs. For instance, the Worcester Bosch Greenstar CDi Compact stands out with its smaller height and higher flow rate, making it a great option for homes with higher hot water demands. However, choosing the right boiler isn’t just about one feature – consider how much hot water you need and the space you have available. This comparison is a starting point to guide you toward a compact and efficient heating solution.
Conclusion
Compact boilers offer a smart solution for saving space and boosting efficiency. By eliminating bulky water tanks, they deliver instant hot water without taking up much room.
Modern condensing compact boilers typically achieve efficiency ratings between 90% and 94%. Switching to a high-efficiency model can cut energy bills by as much as $550 annually. Considering that heating accounts for about 77% of a typical home’s yearly gas usage, choosing the right boiler can lead to noticeable savings. This makes selecting the right model a key decision for any homeowner.
Before purchasing, it’s essential to measure your available space – standard cupboard depths are usually around 11.8 inches. Be sure to account for hinges, pipework, and back panels. Choose the appropriate output: 24–28 kW is ideal for small apartments, while 30–35 kW suits larger homes with multiple showers. Also, ensure your mains water pressure is sufficient.
Professional installation and regular servicing are crucial. With complexities like gas safety, wiring, and venting, only a Gas Safe registered engineer should handle installation. Manufacturers often require annual servicing to maintain warranty coverage. As Gas Safe Engineer Stephen Day explains:
"Annual servicing by a Gas Safe registered engineer is commonly required to keep warranty cover valid."
Routine maintenance ensures safety devices function properly, maintains system pressure, and prevents issues like sludge or limescale buildup. Keeping the service area clear also helps extend the boiler’s lifespan.
For those in the Chicagoland area, Eco Temp HVAC offers expert services to keep your compact boiler running smoothly. Their certified technicians, including Navien Service Specialists, provide comprehensive heating solutions and 24/7 support across Chicago, St. Charles, Bartlett, Lemont, Downers Grove, and Palatine. With professional care, your compact boiler can deliver safe and efficient performance for years to come.
FAQs
How do I choose the right boiler size (kW) for my home?
To choose the right boiler size (kW), think about your home’s size, how many bathrooms you have, and your hot water usage. Larger homes or those with several bathrooms often need boilers with higher kW ratings, while smaller homes typically require less power. For most small to medium-sized homes, boilers in the 24-30 kW range are a good fit. It’s always a smart idea to consult a professional to ensure the boiler is appropriately sized for efficient heating, sufficient hot water, and better energy efficiency.
Can a compact combi boiler handle two showers at the same time?
A compact combi boiler is often capable of managing two showers at the same time, provided it delivers enough flow rate and power. However, its performance largely depends on the specific model and how much hot water your household typically uses. To get the best results, make sure the boiler’s features align with your requirements.
What extra space and clearances are needed for a boiler in a cupboard?
When placing a boiler in a cupboard, make sure to follow these clearance guidelines:
- Front: Leave 12–24 inches of space for servicing.
- Sides: Maintain 4–6 inches of clearance on each side.
- Top: Ensure at least 12 inches of space above the boiler.
- Back: Allow roughly 27.5 inches for maintenance access.
Additionally, the cupboard should have a removable door and allow adequate air circulation. This ensures safe operation and makes maintenance tasks easier.
