Top 35kW System Boilers in 2024 | Efficient Heating Solution

A 35kW system boiler is a powerful and efficient heating solution designed for larger homes with significant hot water and heating demands. Combining robust performance with advanced technology, these boilers are capable of supporting multiple radiators and providing instant hot water for households with several bathrooms or high simultaneous usage.

Unlike traditional boilers, system boilers incorporate essential components, such as the pump and expansion vessel, within the unit, simplifying installation and maintenance. With a focus on energy efficiency, many 35kW system boilers are ErP A-rated, helping homeowners reduce energy bills and minimise their environmental impact. Whether you’re upgrading your current heating system or installing a new one, a 35kW system boiler offers reliability, performance, and convenience for modern living.

What is a 35kW System Boiler?

A 35kW system boiler is a type of boiler that delivers 35 kilowatts (kW) of power and is designed to heat water for both central heating and hot water storage, using a separate hot water cylinder (but without the need for a cold water storage tank, as it draws water directly from the mains). The power output of 35kW means that it can provide enough energy to heat large homes with multiple radiators and bathrooms.

Top 35kW System Boilers and their Price

1. Vokera Evolve S 35kW System Gas Boiler

The Vokèra Evolve S 35kW System Gas Boiler is a high-efficiency system boiler designed for larger homes. It is part of Vokèra’s Evolve range, which offers advanced features and reliable performance.

Cost of the Vokèra Evolve S 35kW System Gas Boiler:

Approximate Boiler Cost: £800 – £1,200
Installation Costs: £600 – £1,200
Total Estimated Cost: £1,400 – £2,400

Key Features of the Vokèra Evolve S 35kW System Gas Boiler:
Efficiency:
ErP A-rated for both heating and hot water, ensuring high energy efficiency.
Seasonal space heating efficiency of 94%, helping to reduce energy bills.
Output:
A 35kW power output, suitable for large homes with 15-20 radiators and multiple bathrooms.
Modulation Ratio:
High modulation ratio of 1:7, which means the boiler adjusts its output to match the heating demand, leading to better efficiency and reduced wear and tear.
Compact Design:
Despite its high power, it has a compact design, making it easier to install in a variety of spaces.
Built-In Weather Compensation:
Includes weather compensation, which adjusts the boiler’s performance based on external temperatures, further improving efficiency.
Smart Controls Compatibility:
Compatible with Vokèra’s BeSMART internet-connected thermostat, allowing remote control and better energy management.
Warranty:
Comes with a standard 10-year warranty when installed by a Vokèra accredited installer, providing peace of mind.
Low NOx Emissions:
Designed to meet low nitrogen oxide (NOx) emission standards, making it environmentally friendly.

2. Worcester Bosch Greenstar 8000 Life 35kW System Gas Boiler

The Worcester Bosch Greenstar 8000 Life 35kW System Gas Boiler is a premium model in Worcester Bosch’s Greenstar range, designed for efficiency, durability, and advanced functionality. It is a popular choice for larger homes requiring reliable heating and hot water.

Cost of the Worcester Bosch Greenstar 8000 Life 35kW System Gas Boiler:

Approximate Boiler Cost: £900 – £1,300
Installation Costs: £700 – £1,300
Total Estimated Cost: £1,600 – £2,600

Key Features of the Worcester Bosch Greenstar 8000 Life 35kW System Gas Boiler:
Efficiency:
ErP A-rated for both heating and hot water.
Up to 94% energy efficiency, making it highly cost-effective and eco-friendly.
Power Output:
The 35kW output is ideal for homes with high heating demands, such as those with 15-20 radiators and multiple bathrooms.
Modern Design:
A sleek, modern appearance with a white or black casing, suitable for visible installations.
Quiet Operation:
One of Worcester Bosch’s quietest boilers, ensuring it won’t disturb household activities.
Enhanced Controls:
Compatible with smart thermostats such as the Worcester Bosch EasyControl, allowing for remote management and improved efficiency.

Built-In Features:
Weather Compensation: Adjusts performance based on outside temperatures to optimise efficiency.
Modulation Technology: The boiler can modulate its power output from 1:10, meaning it adapts to the specific heating demands of the home, improving efficiency and reducing energy waste.
Design & Accessibility:
The new design includes an improved interface for easy operation, maintenance, and servicing.
It features a full-colour display, making diagnostics and settings easy to manage.
Warranty:
Comes with a standard 10-year guarantee when installed by a Worcester Bosch accredited installer, providing long-term peace of mind.
Low NOx Emissions:
Built with Class 6 low NOx emissions, which makes it eco-friendly and compliant with environmental regulations.
Robust Internal Components:
Worcester Bosch is known for using high-quality materials, ensuring a durable and long-lasting boiler.

3. Grant Vortex Eco Utility 35kW System Oil Boiler

The Grant Vortex Eco Utility 35kW System Oil Boiler is part of Grant’s highly efficient Vortex range, designed for homes that are off the gas grid and use oil for heating. This system boiler is known for its excellent efficiency, reliable performance, and compatibility with low-temperature heating systems.

Cost the Grant Vortex Eco Utility 35kW System Oil Boiler:

Approximate Boiler Cost: £700 – £1,100
Installation Costs: £600 – £1,200
Total Estimated Cost: £1,300 – £2,300

Key Features of the Grant Vortex Eco Utility 35kW System Oil Boiler:
Efficiency:
ErP A-rated for heating with a high seasonal efficiency of up to 91.7%, reducing fuel consumption and energy bills.
Incorporates Grant’s Vortex condensing technology, which recycles heat from the flue gases, enhancing efficiency.
Power Output:
The 35kW power output is suitable for large homes with multiple bathrooms and a high number of radiators (15-20 or more), offering efficient heating for sizable properties.
Compact Design:
The utility model is designed for installation in utility rooms, with a simple and functional design.
Its compact size allows for flexible installations, especially in homes where space is limited.
Whisper-Quiet Operation:
The boiler is designed to operate quietly, minimising disruption in the home.
Condensing Technology:
The Vortex system uses condensing technology to recover heat from exhaust gases, significantly improving efficiency and reducing running costs.
Oil-Fired:
It runs on oil, making it ideal for homes that are not connected to the main gas network.
Durability:
Built with high-quality, corrosion-resistant materials, ensuring long-lasting durability and a high level of reliability.
Sealed System:
The boiler works with a pressurised system, which removes the need for a separate expansion tank, simplifying installation and saving space.
Warranty:
Offers a 5-year guarantee on the heat exchanger (when registered), providing assurance of the boiler’s longevity.
Environmentally Friendly:
The boiler has low NOx emissions to comply with modern environmental standards, reducing its impact on the environment.

4. Viessmann Vitodens 200-W 35kW Combi Gas Boiler

The Viessmann Vitodens 200-W 35kW Combi Gas Boiler is a premium, high-efficiency combi boiler that combines heating and hot water in one unit, eliminating the need for a separate hot water cylinder. It’s designed for larger homes with significant heating and hot water demands, and it incorporates advanced technology for superior performance, efficiency, and control.

Cost the Viessmann Vitodens 200-W 35kW Combi Gas Boiler:
Approximate Boiler Cost: £1,000 – £1,500
Installation Costs: £700 – £1,500
Total Estimated Cost: £1,700 – £3,000

Key Features of the Viessmann Vitodens 200-W 35kW Combi Gas Boiler:
Efficiency:
ErP A-rated for both heating and hot water efficiency.
It has a high efficiency rating of up to 98% (seasonal efficiency), significantly reducing energy consumption and bills.
Power Output:
The 35kW output provides ample heating for large homes with 15-20 radiators and can handle high hot water demands, including simultaneous use of taps and showers.
Lambda Pro Plus Combustion Control:
This innovative technology automatically adjusts the air/gas mixture to maintain maximum efficiency, even when gas quality or supply conditions vary.
Modulation Ratio:
Boasts an impressive modulation ratio of 1:17, allowing the boiler to adjust its output efficiently based on demand, reducing wear and tear and enhancing overall efficiency.
Touchscreen Control:
The 7-inch colour touchscreen offers intuitive control over the boiler, with the option to access diagnostics and settings easily.
Smart Home Integration:
Compatible with the ViCare Thermostat and mobile app, allowing you to control your heating remotely, enhancing comfort and efficiency.
Quiet Operation:
The Vitodens 200-W is designed to operate very quietly, making it ideal for installation within living spaces.
Compact Design:
Despite its powerful output, the boiler is compact and can be installed in various locations, including kitchen cupboards or utility rooms.
Inox-Radial Stainless Steel Heat Exchanger:
Viessmann’s unique stainless steel heat exchanger is corrosion-resistant and highly durable, ensuring long-lasting performance and efficient heat transfer.
Weather Compensation:
Built-in weather compensation automatically adjusts heating performance based on outdoor temperatures, enhancing comfort and reducing energy consumption.
Warranty:
Comes with a 5-year warranty as standard, extendable to 10 years if installed by a Viessmann trained installer.
Low NOx Emissions:
This boiler is built to meet Class 6 low NOx emission standards, making it environmentally friendly and compliant with regulations.

5. Vaillant ecoTEC plus 835 Combi Gas Boiler

The Vaillant ecoTEC plus 835 Combi Gas Boiler is a highly efficient and reliable boiler from Vaillant’s ecoTEC range, designed to meet the heating and hot water demands of larger homes. With a compact design and advanced features, it provides efficient heating while maintaining ease of use.

Cost the Vaillant ecoTEC plus 835 Combi Gas Boiler:

Approximate Boiler Cost: £800 – £1,300
Installation Costs: £600 – £1,300
Total Estimated Cost: £1,400 – £2,600

Key Features of the Vaillant ecoTEC plus 835 Combi Gas Boiler:
Efficiency:
ErP A-rated for heating and hot water efficiency.
Offers an energy efficiency of up to 94%, ensuring lower energy bills and reduced environmental impact.
Power Output:
The 35kW output is perfect for medium to large-sized homes with 15-20 radiators and high hot water demand, such as multiple bathrooms.
Capable of delivering a flow rate of 14.3 litres per minute, making it suitable for homes with simultaneous use of taps or showers.
AquaComfort System:
Provides instant hot water at a consistent temperature without long delays, thanks to the built-in AquaComfort system.
Modulation Technology:
Features a 1:6 modulation ratio, meaning the boiler can efficiently adjust its output based on the home’s heating demand, reducing energy waste and prolonging the boiler’s lifespan.
Quiet Mark Accreditation:
Designed for quiet operation, the ecoTEC plus 835 is Quiet Mark accredited, meaning it operates silently in the background and can be installed in noise-sensitive areas.
Smart Controls Compatibility:
Fully compatible with Vaillant’s vSMART smart thermostat and other smart home devices, allowing you to control your heating remotely for maximum efficiency and comfort.
Compact Size:
Its compact and space-saving design allows for flexible installations, including within kitchen cupboards or utility rooms, without compromising performance.
Integrated Efficiency Features:
The ecoTEC plus 835 includes advanced features like a high-efficiency pump, contributing to lower energy usage and better heating performance.
Advanced diagnostics help engineers quickly identify issues during servicing, minimising downtime.
Low NOx Emissions:
Designed to meet Class 6 low NOx emissions, making it an environmentally friendly choice that adheres to modern regulations.
Warranty:
Comes with a standard 5-year warranty, extendable up to 10 years when installed by a Vaillant Advance installer, ensuring long-term peace of mind.

Choosing the Right 35kW System Boiler for Your Home

Choosing the right 35kW system boiler for your home requires careful consideration of various factors such as energy efficiency, compatibility with your property, the boiler’s features, and your budget.

Your Home’s Heating Requirements

A 35kW system boiler is suitable for large homes with 15-20 radiators and multiple bathrooms. Ensure that your home’s heating and hot water demands justify the need for a boiler of this size.

System boilers are ideal for homes with high hot water demand, especially those with multiple bathrooms where water usage may occur simultaneously.

Energy Efficiency

Boilers with an ErP (Energy-related Products Directive) A-rating for both heating and hot water will ensure lower energy bills and reduced carbon footprint. Most modern boilers, including those mentioned, feature condensing technology, which recovers heat from flue gases, increasing efficiency.

Boiler Size and Location

If space is limited, opt for a model with a compact design that can fit into a kitchen cupboard or utility room. Models like the Vaillant ecoTEC plus 835 and Viessmann Vitodens 200-W are known for their space-saving designs.

Models like the Grant Vortex Eco Utility 35kW Oil Boiler are designed for utility room installations, whereas gas boilers like the Worcester Bosch Greenstar 8000 Life can be installed more flexibly.

Smart Controls and Modulation

Boilers that support smart controls, such as the Viessmann Vitodens 200-W and Worcester Bosch Greenstar 8000, allow you to control heating remotely, improving convenience and energy efficiency.

A higher modulation ratio (e.g., Viessmann Vitodens 200-W has 1:17) ensures the boiler operates efficiently by adjusting its output to match demand, reducing wear and tear and cutting down on energy usage.

Fuel Type

Choose between gas or oil-fired systems based on your property’s connection to the main gas grid. Gas boilers like the Vokèra Evolve S 35kW are suitable for homes with gas connections, while oil boilers like the Grant Vortex Eco Utility are ideal for off-grid homes.

Noise Levels

For homes where the boiler is installed near living spaces, noise levels should be a consideration. The Vaillant ecoTEC plus 835 is a Quiet Mark accredited model, ensuring silent operation.

Environmental Impact

Choose a boiler with low nitrogen oxide (NOx) emissions, as this will reduce its environmental impact and ensure compliance with regulations. All the boilers in this list meet modern NOx standards.

FAQs

Do I need a 35kW boiler?

A 35kW boiler is typically needed for large homes with 15-20 radiators and high hot water demands (e.g., multiple bathrooms).

How much gas does a 35kW boiler use?

A 35kW boiler uses 3.5 cubic metres of gas per hour when running at full capacity (assuming 100% efficiency).

How many radiators can a 35kW system boiler run?

A 35kW system boiler can comfortably run 15-20 radiators in a large property.

Job Description	Labour Cost	Supply Cost	Total Cost
Fixing stuck/faulty port valves	£30 – £120	N/A	£30 – £120
Replacing stuck/faulty port valves	£30 – £120	£40 – £90	£70 – £210
Removing dust/debris from thermostat	£30 – £60	N/A	£30 – £60
Fixing faulty thermostat connections/wiring	£30 – £120	£10 – £30	£40 – £150
Replacing a thermostat	£30 – £120	£80 – £240	£110 – £360
Fixing a faulty PCB	£60 – £240	N/A	£60 – £240
Replacing a faulty PCB	£60 – £240	£430 – £560	£490 – £800
New boiler installation	£250 – £1,000	£550 – £1,800	£800 – £2,800

Discovering a leak beneath your boiler can be alarming and inconvenient. Whether it’s a minor drip or a significant puddle, understanding the cause and appropriate response is crucial for maintaining a safe and efficient heating system. This guide explores the common reasons behind boiler leaks, assesses their severity, and provides actionable solutions. Additionally, it outlines the costs associated with repairs and replacements, helping you make informed decisions about your heating system.

The Implications of a Leaking Boiler

A leaking boiler is not merely a nuisance—it signals underlying issues that could escalate if left unattended. Water leaks can lead to:

Structural Damage: Persistent leaks can weaken floors, walls, and ceilings.
Increased Energy Bills: Inefficiencies caused by leaks can result in higher energy consumption.
Safety Hazards: Although rare, significant leaks may pose electrical risks or contribute to mold growth.
Disrupted Comfort: A malfunctioning boiler can lead to inadequate heating and hot water supply.

Given these potential risks, addressing a boiler leak promptly is essential to ensure your home’s safety and comfort.

Identifying the Source of the Leak

Before undertaking any repairs, pinpointing the exact source of the leak is vital. Common leak origins include:

Underneath the Boiler: Often due to corroded or poorly installed pipework.
Pressure Relief Valve (PRV): Excessive pressure can cause the PRV to release water.
Heat Exchanger: Cracks or faults in the heat exchanger can lead to leaks.
Internal Seals: Degraded seals within the boiler may allow water to escape.

Inspecting for Leaks

Visual Inspection: Examine the area around the boiler for water trails or puddles.
Pipework Check: Look for corrosion, loose joints, or damaged pipes beneath the boiler.
Pressure Gauge Monitoring: Regularly check the boiler’s pressure gauge to identify irregularities.
Listen for Unusual Sounds: Hissing or dripping noises can indicate a leak.

Read more about: What to do if you have a leaking boiler

Common Causes of Boiler Leaks

1. Corroded or Faulty Pipework

Corrosion: Over time, water and metallic debris can corrode copper pipes, creating gaps through which water can escape.

Poor Installation: Incorrectly fitted joints or inadequate sealing during installation can lead to leaks.

Solution: Corroded pipes often require replacement by a certified engineer. In cases of minor leaks, tightening connections may suffice, but extensive corrosion typically necessitates pipework overhaul.

2. High Boiler Pressure

Excessive Pressure: Boilers operate optimally within specific pressure ranges. High pressure can trigger the PRV to release water to prevent system damage.

Causes: Overfilled systems, faulty expansion vessels, or malfunctions in pressure regulation can cause elevated pressure levels.

Solution: Reducing boiler pressure involves bleeding radiators to release excess water and ensuring the filling loop is properly closed. Persistent high pressure may require professional assessment to identify and rectify underlying issues.

3. Faulty Heat Exchanger

Function: The heat exchanger transfers heat from the burner to the water circulating through the system.

Issues: Cracks or faults in the heat exchanger can cause water to leak, often signaling severe boiler malfunction.

Solution: A compromised heat exchanger usually necessitates replacing the boiler, as repairs can be prohibitively expensive and unreliable.

4. Degraded Internal Seals

Seals’ Role: Internal seals prevent water from leaking out of various boiler components.

Degradation: Over time, seals can wear out or become brittle, leading to leaks.

Solution: Replacing faulty seals requires professional expertise. In some cases, extensive seal degradation may warrant a complete boiler replacement.

5. Airlocks in the System

Airlocks: Trapped air within the heating system can disrupt water flow, causing localized leaks.

Solution: Bleeding radiators to release trapped air can resolve minor leaks caused by airlocks. Persistent issues may require a system flush or professional intervention.

DIY Solutions for Minor Leaks

While some boiler leaks demand professional attention, certain minor issues can be addressed independently:

Tightening Connections: Carefully tightening loose pipe joints may stop minor leaks.
Bleeding Radiators: Removing trapped air can alleviate leaks caused by airlocks.
Using Sealants: For small pinhole leaks, specialized boiler sealants can temporarily contain the leak until professional repairs are made.

Caution: Always turn off the boiler and allow it to cool before attempting any DIY fixes. If unsure, it’s safer to consult a certified engineer to prevent further damage or safety risks.

When to Seek Professional Help

Certain scenarios require immediate professional intervention:

Persistent Leaks: Ongoing leaks despite DIY attempts indicate more serious issues.
Heat Exchanger Faults: Cracked or faulty heat exchangers necessitate expert repairs or boiler replacement.
High Pressure Problems: Continuous high pressure can damage the boiler and pose safety risks.
Complex Corrosion: Extensive pipe corrosion often requires comprehensive system repairs beyond basic fixes.

Read about: Boiler Replacement And Boiler Repair

How long does it take to fit a new boiler?

Cost of Repairing a Leaking Boiler

Repair costs vary based on the leak’s origin and severity:

Minor Pipe Leaks: £80 – £150
Pressure Relief Valve Replacement: £120 – £250
Heat Exchanger Repair/Replacement: £500 – £1,500
System Flush: £200 – £400
Full Boiler Replacement: £800 – £3,000

Note: Prices fluctuate based on boiler type, location, and the extent of the damage. Obtaining multiple quotes from certified engineers ensures competitive pricing and quality service.

Deciding Between Repair and Replacement

Evaluating whether to repair or replace your boiler involves several considerations:

Age of the Boiler: Boilers over 10-15 years old are less efficient and more prone to breakdowns, often making replacement more cost-effective.
Frequency of Repairs: Recurrent issues indicate declining reliability, favoring a new boiler installation.
Repair Costs: High repair costs for critical components like heat exchangers may justify replacement.
Energy Efficiency: Upgrading to a modern, high-efficiency boiler can reduce energy bills and environmental impact.

Read about: Swift Emergency Boiler Repair Service

Benefits of Upgrading to a New Boiler

Investing in a new boiler offers multiple advantages:

Enhanced Efficiency: Modern boilers achieve higher energy efficiency, leading to lower utility bills.
Improved Reliability: New boilers are less likely to experience frequent breakdowns.
Advanced Features: Features like smart thermostats and improved controls enhance user experience and system performance.
Environmental Impact: High-efficiency boilers produce fewer emissions, contributing to a greener environment.
Warranty Coverage: New boilers come with extended warranties, providing peace of mind and protection against future issues.

Financial Assistance for Boiler Replacement

Replacing a boiler can be a significant investment, but various financial options can ease the burden:

LETsheat Financing: Offers flexible payment plans, including interest-free options, allowing homeowners to spread the cost over manageable monthly installments.
Government Grants: Certain regions provide incentives for upgrading to energy-efficient boilers, reducing overall costs.
Trade Discounts: Some providers offer discounts for new installations, bundling services, or referring friends and family.

Choosing the Right Boiler Replacement Service

Selecting a reputable service provider ensures a smooth and efficient boiler replacement process:

Certification and Licensing: Ensure the engineer is Gas Safe registered to comply with safety standards.
Customer Reviews: High ratings on platforms like Trustpilot indicate reliable and quality service.
Warranty and Support: Look for extended warranties and comprehensive after-sales support.
Transparent Pricing: Providers like LETsheat offer fixed price guarantees and price match promises to ensure competitive pricing.
Installation Speed: Quick installation services, such as 24-hour installation, minimize downtime and restore heating promptly.

Advantages of LETsheat for Boiler Repairs and Replacements

LETsheat distinguishes itself as a leading provider for boiler solutions through several key offerings:

Rapid Installation: Guaranteed installation within 24 hours ensures minimal disruption.
Customer Satisfaction: With thousands of positive reviews and a Trustpilot rating of 4.9, LETsheat excels in customer service.
Price Match Guarantee: LETsheat matches any like-for-like quotes, ensuring competitive pricing.
Flexible Financing: Multiple payment options, including interest-free plans, make boiler replacements more accessible.
Extended Warranties: Up to a 12-year guarantee on selected boilers offers long-term protection and peace of mind.
Trusted Trader Status: Recognition as a Which? Trusted Trader underscores LETsheat’s reliability and quality.

Read about: Step-by-Step Guide to Boiler Installation | Expert Tips

Preventative Measures to Avoid Future Leaks

Implementing regular maintenance practices can significantly reduce the likelihood of encountering boiler leaks:

Annual Servicing: Schedule yearly inspections with a certified Gas Safe engineer to identify and address potential issues early.
System Flushing: Periodically flush your heating system to remove sludge and limescale, maintaining clean and unobstructed pipes.
Monitor Pressure Levels: Regularly check the boiler’s pressure gauge and adjust as needed to prevent over-pressurization.
Inspect Pipework: Routinely examine pipe connections for signs of corrosion or wear, addressing minor issues before they escalate.
Install a Magnetic Filter: LETsheat includes a magnetic filter with installations to capture metallic debris, prolonging boiler lifespan and preventing blockages.

Conclusion

A leaking boiler is a clear indicator that your heating system requires attention. Whether the issue stems from corroded pipes, high pressure, faulty heat exchangers, or degraded seals, understanding the root cause is essential for effective resolution. While minor leaks can sometimes be managed through DIY methods, significant issues often necessitate professional intervention to ensure safety and compliance with regulations.

Investing in a new boiler offers numerous benefits, including enhanced efficiency, improved reliability, and reduced energy costs. Platforms like LETsheat provide comprehensive solutions, from swift installations and competitive pricing to extended warranties and flexible financing options, making boiler replacements accessible and affordable.

Regular maintenance and proactive upgrades not only prevent leaks but also contribute to a more sustainable and cost-effective heating system. By choosing a reputable service provider and adhering to best practices, homeowners can ensure their boilers operate efficiently, providing consistent warmth and peace of mind throughout the colder months.

FAQs

What causes a boiler to leak?

Boiler leaks can result from issues like corrosion, high pressure, damaged seals, or cracked components. Regular maintenance can help prevent leaks.

How much does it cost to repair a leaking boiler?

Repair costs for a leaking boiler vary depending on the issue’s severity, typically ranging from $100 to $500 for common repairs.

Can I use my boiler if it’s leaking?

It’s recommended not to use a leaking boiler, as continued use can lead to further damage or safety issues. Always consult a professional for repairs.

How can I prevent boiler leaks?

Regular boiler maintenance, annual inspections, and pressure checks can help prevent leaks by identifying and addressing potential issues early.

Best 35kW System Boilers for Efficient Home Heating

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