5 Best Conventional Boilers [2026]

Identifying the best conventional boilers is essential for homeowners and landlords who wish to maintain an efficient heating system without the upheaval of a full pipework overhaul. Also known as regular or heat-only boilers, these units are the backbone of traditional UK heating systems that utilise a cold water storage tank and a separate hot water cylinder.

Whether you are managing a large family home with high hot water demand or a rented property where reliability is paramount, choosing a top-tier brand ensures your central heating remains robust for years to come.

5 Best Conventional Boilers: At A Glance

The best conventional boilers currently available in the UK combine peak seasonal efficiency with extended manufacturer guarantees to provide long-term peace of mind. The following table summarises the top performers based on reliability, engineer recommendations, and value for money.

Boiler Model	Output Range (kW)	Efficiency	Max Guarantee	Which? Score	Trustpilot
Worcester Bosch Greenstar Ri	9kW – 30kW	92%	12 Years	Best Buy	4.6/5
Viessmann Vitodens 100-W	11kW – 32kW	98%	12 Years	Recommended	4.4/5
Vaillant ecoTEC plus Regular	12kW – 35kW	94%	10 Years	Best Buy	4.5/5
Ideal Logic² Max Heat	12kW – 30kW	93%	10 Years	Best Buy	4.8/5
Baxi 800 Heat	16kW – 30kW	93%	10 Years	Top Rated	4.5/5

1. Worcester Bosch Greenstar Ri

The Worcester Bosch Greenstar Ri is widely considered the best conventional boiler for most UK homes due to its compact dimensions and the brand’s legendary after-sales support. This model is designed specifically to fit into a standard kitchen cupboard, making it a “fit and forget” solution for many.

Specs, Features, And Technology

This boiler features a high-grade aluminium-silicon heat exchanger, which is known for its excellent thermal conductivity. It is hydrogen-ready for a 20% blend and is fully compatible with solar thermal installations, allowing you to further reduce your carbon footprint. The user interface is straightforward, focusing on simple dial controls that are accessible to everyone.

Efficiency

The Greenstar Ri operates at an ErP A-rating, achieving 92% efficiency. It modulates its output to match the heating demand of the property, ensuring that gas isn’t wasted during milder weather.

Estimated Costs

• Boiler Unit Only: £900 – £1,300
• Installed Cost: £2,100 – £3,400
• Running Costs: Low, especially when paired with Bosch’s smart controls.

Which? And Trustpilot Ratings

Worcester Bosch has held the Which? Best Buy status for over a decade, with a Trustpilot rating of 4.6/5. Engineers frequently praise the availability of spare parts and the ease of servicing this particular model.

2. Viessmann Vitodens 100-W Heat Only

The Viessmann Vitodens 100-W is the best conventional boiler for homeowners who prioritise engineering excellence and the highest possible fuel savings. This German-engineered unit is distinct because it uses premium materials usually reserved for much more expensive commercial systems.

Specs, Features, And Technology

The standout feature is the Inox-Radial stainless steel heat exchanger. Unlike aluminium variants, stainless steel is highly resistant to corrosion and “self-cleans” as the boiler operates.

It also includes the MatriX-Plus burner and Lambda Pro combustion control, which automatically adjusts the gas-to-air mix to maintain peak performance even if gas quality fluctuates.

Efficiency

This is one of the most efficient regular boilers on the market, with potential seasonal efficiency reaching 98%. This high level of heat recovery means more of the gas you pay for is converted into warmth rather than lost through the flue.

Estimated Costs

• Boiler Unit Only: £1,050 – £1,450
• Installed Cost: £2,200 – £3,600
• Running Costs: Exceptional; it typically offers the lowest lifetime running costs in its class.

Which? And Trustpilot Ratings

Viessmann is a Which? Recommended Brand and holds a Trustpilot score of 4.4/5. It is highly favoured by specialist heating engineers who appreciate the durability of its internal components.

3. Vaillant ecoTEC plus Regular

The Vaillant ecoTEC plus Regular is often cited as the best conventional boiler for those who want a quiet, high-performance heating system. Vaillant’s reputation for build quality makes this a staple choice for premium home renovations and landlord upgrades alike.

Specs, Features, And Technology

This boiler utilises IoniDetect technology, which allows the unit to monitor the quality of the gas flame and adapt accordingly. It is remarkably quiet, holding the Quiet Mark accreditation, which is ideal if your boiler is located near a bedroom or living area. It also features a large, backlit display that provides clear diagnostic information.

Efficiency

With a seasonal efficiency of 94%, the ecoTEC plus ensures your gas consumption is kept to a minimum. It is an A-rated appliance that meets all current ErP directives for energy performance.

Estimated Costs

• Boiler Unit Only: £1,000 – £1,500
• Installed Cost: £2,300 – £3,700
• Running Costs: Competitive, particularly when used with Vaillant’s vSMART app-based controls.

Which? And Trustpilot Ratings

Vaillant consistently receives the Which? Best Buy award and maintains a strong Trustpilot rating of 4.5/5. Customers frequently highlight the professional level of customer service provided during the warranty period.

4. Ideal Logic² Max Heat

The Ideal Logic² Max Heat is arguably the best conventional boiler for those seeking British-made reliability with an industry-leading warranty package included as standard. Based in Hull, Ideal has designed this boiler to be incredibly user-friendly for both the homeowner and the installer.

Specs, Features, And Technology

The “Max” version of this boiler comes with a high-quality Ideal System Filter in the box. This filter protects the boiler from “sludge” and debris in the pipework, which is the leading cause of boiler failure. It has a large, high-definition colour display and is fully compatible with the Halo smart thermostat range.

Efficiency

The Logic² Max Heat is A-rated for heating efficiency, typically sitting at 93%. Its compact design does not compromise its ability to modulate down to very low outputs, preventing “cycling” and reducing wear on the burner.

Estimated Costs

• Boiler Unit Only: £850 – £1,200
• Installed Cost: £2,000 – £3,100
• Running Costs: Very affordable, with maintenance made easier by the included system filter.

Which? And Trustpilot Ratings

Ideal Heating currently holds one of the highest Trustpilot ratings in the industry at 4.8/5. It is also a Which? Best Buy recipient, noted for its ease of repair and the widespread availability of spares.

5. Baxi 800 Heat

The Baxi 800 Heat is the best conventional boiler for those who want a no-nonsense, reliable unit that is built to last. Baxi is a household name in the UK, and the 800 series represents their premium offering in the heat-only category.

Specs, Features, And Technology

Like the Ideal Max, the Baxi 800 comes with an ADEY Micro2 magnetic system filter to ensure the longevity of the heat exchanger. It is incredibly lightweight (starting at just 19.5kg), making it an easy installation for engineers in tight loft spaces or cupboards. 

It also features a “central flue” design, which often makes it a direct replacement for older, discontinued models without needing to move pipework.

Efficiency

This boiler is ErP A-rated with an efficiency of 93%. It is designed to be highly responsive, providing heat to your radiators almost instantly when the programmer kicks in.

Estimated Costs

• Boiler Unit Only: £950 – £1,300
• Installed Cost: £2,100 – £3,300
• Running Costs: Reliable and predictable, fitting well into a standard maintenance budget.

Which? And Trustpilot Ratings

Baxi is highly regarded for its customer support and holds a Trustpilot rating of 4.5/5. It is frequently chosen by landlords who need a dependable boiler with a long-term parts and labour guarantee.

How To Choose The Best Conventional Boilers?

Selecting the best conventional boilers for your home involves more than just picking the brand with the longest warranty. You must evaluate your property’s size, your hot water usage, and your existing system’s compatibility.

• Choose the Worcester Bosch Greenstar Ri if… you have limited space and need a compact boiler that fits inside a standard kitchen cupboard while still being backed by the UK’s most famous heating brand.
• Don’t choose the Worcester Bosch Greenstar Ri if… you live in a very hard-water area and want a stainless steel heat exchanger for maximum mineral resistance.
• Choose the Viessmann Vitodens 100-W if… you want the absolute pinnacle of efficiency and a boiler that is built with commercial-grade stainless steel for a longer lifespan.
• Don’t choose the Viessmann Vitodens 100-W if… you prefer a brand where every local independent plumber is guaranteed to carry spare parts in their van.
• Choose the Vaillant ecoTEC plus if… the boiler is located near a bedroom and you require the quietest operation possible, as evidenced by its Quiet Mark status.
• Don’t choose the Vaillant ecoTEC plus if… you are on a strict budget, as Vaillant sits at the more premium end of the pricing scale.
• Choose the Ideal Logic² Max Heat if… you want the best “all-in-one” value package that includes a magnetic filter and a 10-year warranty as standard.
• Choose the Baxi 800 Heat if… you are replacing an older Baxi or Potterton boiler and want a simple, lightweight unit that minimises installation labor costs.

Looking For A New Boiler Quote?

Upgrading to a high-efficiency regular boiler is one of the smartest investments you can make for your home’s infrastructure. If your current system is over 10 years old, it is likely operating at 70% efficiency or less, meaning you are losing 30p of every pound spent on gas. 

By requesting a new boiler quote today from Boilers 2 Go, you can take the first step toward a warmer, more energy-efficient home. Our experts will help you navigate the various outputs and brands to find the perfect fit for your traditional open-vented system.

FAQs

Can I use a conventional boiler with underfloor heating?

Yes, conventional boilers are perfectly suitable for underfloor heating (UFH) systems. Because they work by heating a large volume of water stored in a cylinder, they can provide the consistent, low-temperature flow required for UFH manifolds. You simply need to ensure your installer fits the correct mixing valves to manage the water temperature effectively.

Is it possible to convert a conventional boiler to a combi later?

It is possible to convert a conventional system to a combi, but it is a significant job. It involves removing the cold water tanks in the loft and the hot water cylinder, then re-routing the pipework to accept high-pressure mains water. If you think you might want a combi in the future, it is often cheaper to do the conversion at the same time you install your new boiler.

Do modern conventional boilers still require a header tank?

Modern regular boilers (heat-only) are usually installed as part of an “open-vented” system, which does require a small feed and expansion tank (header tank) in the loft. However, some models can be “sealed” using an external expansion vessel and filling loop, which removes the need for the loft tanks while still using your existing hot water cylinder.

How do I know if my conventional boiler is hydrogen-ready?

Most “best conventional boilers” manufactured from 2024 onwards are certified as “20% hydrogen-ready.” This means they have been tested to run on a blend of natural gas and 20% hydrogen without any modifications. You can usually find a sticker on the front of the unit or check the manufacturer’s technical data sheet for the “H2 Ready” logo.

Why does my conventional boiler need a separate pump?

Unlike combi or system boilers, which have a pump built into the boiler casing, a conventional boiler (regular) usually relies on an external pump located elsewhere in the airing cupboard. This pump is responsible for circulating the heated water around your radiators and through the coil in your hot water cylinder.