The most efficient combi boilers in 2024 are Worcester Bosch Greenstar 8000, Ideal Logic Max, and Ariston ALTEAS ONE NET.
The most efficient gas boilers in 2024 are Viessmann Vitodens 200-W, Worcester Bosch Greenstar 4000, and Vaillant ecoTec plus.
An A-rated efficient boiler can save you up to £522 per year.
Finding the best energy-efficient boiler is good news for your wallet, your home and the planet. Energy-efficient boilers use less fuel than their non-efficient counterparts. And as they use less fuel, you’ll save on central heating costs.
In even better news, it couldn’t be easier to find an efficient boiler. That’s because all boilers installed in the UK must be condensing. Condensing boilers are far more efficient than the non-condensing boilers that came before them.
We have carefully studied the boiler ratings in the UK to provide you with a list of the most efficient modern boilers.
And with this plethora of choices, for sure you’d want to go for the best energy-efficient boilers only. One surefire way to find the most suitable option is to consult a heating engineer and get boiler quotes.
Yet finding the most efficient boiler can become a daunting task when done alone. You risk getting stuck in a rut of never-ending googling and calls with no actionable contacts at your fingertips. A busy homeowner like you doesn’t have time for that on a Friday night!
Fortunately, Boiler Guide can relieve your stress. By completing our 30-second form you get up to 3 comparison quotes from local engineers. The quotes are free and come with no obligation to accept any of them. Click below to get started!
Boiler efficiency measures how well the boiler turns fuel into usable energy (heat for your home and hot water). Higher boiler energy efficiency generates more heat energy from a specific fuel quantity. This way, the energy consumption numbers drop and energy costs reduce.
In the UK, energy-efficient boilers are rated through the ErP rating. It indicates the proportion of the boiler’s yearly heat production in relation to its total annual consumption of fossil fuel energy.
The rating of 90% signifies that 90% of the fuel energy transforms into warmth for your residence. The remaining 10% dissipates either through the chimney or emanates from the boiler into the surrounding area where the boiler is located.
An A+++ energy classification indicates that an appliance is notably more efficient, surpassing a standard A-rated device by at least 30%. Each additional “+” symbol signifies a 10% increase in energy efficiency compared to the A rating. Consequently, an A+++ rating stands as the highest energy efficiency achievable for a boiler.
Needless to say, the specific energy efficiency rating of a boiler depends on the brand, model, and fuel used.
The most energy-efficient boilers in the UK
What is the most energy-efficient boiler in the UK? It all depends on your needs, housing situation and preferences. However, when looking for the most efficient boiler, it's not all about the performance rating. You also need to make sure the boiler is suited to your home.
That means getting the right type of boiler that's also the right size. And when it comes to boiler type, you have three options: combi, system and regular.
System boilers come with a separate hot water cylinder and suit households with large hot water demands.
And last but not least, conventional boilers (also referred to as regular). They require much space as they come in three parts: the actual boiler, a hot water cylinder, and a water storage tank.
Keep in mind that energy-efficient boiler cost depends on the brand, boiler size, installation requirements, and your housing conditions. The UK government offers multiple boiler grants that can remove a good deal of money from the initial investment.
Alternatively, you can obtain quotes from heating engineers to get the most tailored offer for your situation.
Yet what does it take to get a single quote or a boiler engineer’s contact number? Hours or days of googling, sifting through the reviews, reaching out to installers and vetting them. It's a long plan to type and an even longer (and more tedious) task to do! We bet you'd rather do anything other than this during your valuable free time after work.
Fortunately, Boiler Guide can help you save your time. Simply answer a few quick questions about your boiler situation and we'll connect you with up to 3 heating engineers near you. Compare their quotes with no need to accept any of them. Our offer is free with no obligations. Click below to begin!
Finding the most efficient gas boiler depends on the type you need. Let's break down the best performers in each category.
Viessmann Vitodens 200-W
Output range: 25.4-32kW
Efficiency: 94%
Warranty: 7-12 years
Price range: £1,550-£1,600
Boiler type: combi
The Vitodens combi boiler range by Viessmann is one of the most efficient gas boilers in 2024 in the UK. It’s wall-mounted so it fits properties with limited space and low ceilings.
Moreover, this model is compact, lightweight, and efficient due to its modulating MatriX-Plus cylinder burner and Inox-Radial heat exchanger for efficient and durable operation.
The boiler is equipped with the Lambda Pro Plus combustion controller, which automatically adjusts combustion to changing gas types for consistently high energy efficiency.
Its wide output range makes it the most efficient gas boiler for a large house.
Worcester Bosch Greenstar 4ooo
Output range: 12-24kW
Efficiency: 93%-94%
Warranty: Up to 12 years
Price range: £975-£1,200
Boiler type: system
Greenstar lineup by Worcester Bosch is a contender for the most efficient gas system boiler in the UK. Its Intelligent Filling System monitors the system pressure and automatically re-fills the system to the optimum level.
And its large condensate siphon (500ml) increases the volume of condensate discharge, which reduces the risk of freezing.
Worcester Bosch Greenstar 4000 system gas boiler is considered to be the best all-around combi boiler by Which? platform. It is highly efficient, quiet, and reliable, and it comes with a 12-year warranty. It’s known for its high efficiency and eco-friendliness.
These boilers have a wide power range to meet heating and hot water requirements. Moreover, they are designed to operate well in low-water pressure areas, ensuring powerful water flow and warm showers.
Vaillant ecoTec plus
Output range: 26-40kW
Efficiency: 92%-94%
Warranty: 5-10 years
Price range: £902-£1,537
Boiler type: system
In case you’re looking for energy-efficient and cheap boilers in the UK, look no further than the ecoFIT Pure or ecoTEC plus conventional boiler range from Vaillant boilers.
These boilers boast a high efficiency of 92%-94%. They come with 5-10 years of warranty and cost anywhere between £902-£1,537.
Most efficient combi boilers in 2024
Combi boilers are compact heating systems and as they deliver hot water on demand, they don't need to be fitted alongside a cylinder. So you'll be saving space around your home and money due to the high efficiency of combi boilers.
Combi boilers have quickly become the heating system of choice for UK homeowners and you have no shortage of options. Yet what's the most efficient and best combi boiler as of 2024? Here are our picks.
Ariston ALTEAS ONE NET
Efficiency: 94%
Warranty: 12 years
Output sizes: 28, 30, 31, 35kW
Price: £1,300-£2,000
Key features: Ultra-safe black glass front panel, optional full zone management kit.
Ariston boilers of this type are represented by an award-winning combi boiler Atleas One Net.
Apart from being an energy efficient boiler, its generous warranty also makes it a reliable one.
It boasts a stainless steel heat exchanger and 'Auto Function' that tracks and adjusts the temperature automatically, reducing energy consumption.
Worcester Bosch Greenstar 8000
Efficiency: 93%-94%
Warranty: 7-12 years
Output sizes: 20, 24, 29.2, 30, 30.6, 35kW
Price: £1,200-£2,395
Awards: Best Services Product at the Housebuilder Product Awards
Key features: Optional unique Intelligent Filling System, wireless connectivity with the Bosch EasyControl smart thermostat.
Worcester Bosch Greenstar 8000 boilers come equipped with advanced controls and wireless connectivity. The Greenstar 8000 range boasts an impressive A-rated efficiency rating while also being an excellent hydrogen boiler solution.
So if you’re looking for the most efficient boiler, opt for this powerful model.
Ideal Logic Max
Efficiency: 94%
Warranty: 7-10 years
Output sizes: 24.2, 25.6kW
Price: £968 - £1,156
Awards: Housekeeping Reader Recommended Status (2019, 2020); Queen’s Award for Enterprise and Innovation (2019)
Key features: Boiler frost protection, fault message display, operation modes for summer, winter, and boiler off, and system water pressure monitoring.
Produced for serene operation, the Ideal Logic Max range proves perfect for residences that prioritise minimal noise levels. Enhancing this tranquillity, the Ideal Logic Max System Boiler includes a top-tier Ideal System filter, actively safeguarding the boiler and extending its longevity.
Moreover, multiple awards signify this model might be the most energy-efficient combi boiler in 2024.
Most efficient system boilers in 2024
System boilers are connected to the mains water supply (like combi boilers). This removes the need for a cold water storage tank in the loft, which is the case for regular boilers. But unlike combi boilers, a heating system with a system boiler requires a hot water cylinder.
Domestic hot water is stored in the cylinder until you need it. This does mean extra space is needed but a system boiler can meet a higher demand for hot water.
ATAG iS
Efficiency: 94%
Warranty: 10-14 years
Output sizes: 15kW-40kW
Price: £N/A
Key features: In-built ErP pump to control the heat given out by the boiler for energy efficiency, OneZone Temperature Control using the ATAG One Zone App.
This ATAG boiler comes with a wide range of output options making it one of the most energy-efficient and best boilers to date. This 275 mm (deep) model is available to fit inside kitchen cupboards.
The ATAG ProConnect comes standard with a fixing jig, making the rear piping setup a breeze, and ensuring a neat and tidy installation. Its built-in anti-cycling function enhances system performance by preventing unnecessary cycling, saving energy and optimising your comfort.
The combined condensate and pressure relief valve outlet pipe reduces pipework complexity, ensuring a cleaner, more efficient installation process. Designed for low electrical usage, the ErP pump enhances overall efficiency, ensuring you get the most out of your heating system.
Baxi 800
Efficiency: 93%
Warranty: 10 years
Output sizes: 24kW-30kW
Price: £913-£957
Key features: Adey Micro 2 Filter, EasyFill for the most optimal pressure
This Baxi boiler model comes with the Adey Micro 2 Filter which guarantees optimal performance and durability by preventing unwanted particles from affecting your system’s efficiency.
With EasyFill, you can effortlessly maintain the central heating system pressure, eliminating the need for engineer visits. BAXI's pre-heated condensate trap is meticulously designed to thwart freezing during the colder months, safeguarding your system’s integrity and preventing frozen condensate pipes.
Whether you’re connected to natural gas or LPG, this boiler adapts to your needs without requiring a conversion kit. Also, it’s the most efficient boiler within the under £1000 price range.
Intergas Compact HRE SB
Efficiency: 92%-93%
Warranty: 7 years (10 years on heat exchanger)
Output sizes: 18.7kW-42.5kW
Price: £785-£1,135
Key features: Bithermic heat exchanger for extreme energy efficiency, built-in frost thermostat, hybrid heating system options.
The OpenTherm technology enables seamless communication and control between different components of your heating system for optimised performance and energy efficiency.
The biothermic heat exchanger is crafted from a combination of aluminium and copper which ensures exceptional heat transfer efficiency. Also, the integral expansion vessel ensures that your heating system can handle fluctuations in pressure with ease.
Moreover, Intergas is leading the charge towards a greener future for home heating with the introduction of its Xtend system. This innovative hybrid system takes a groundbreaking approach by combining a gas combi boiler and an air source heat pump (ASHP).
The Xtend system integrates these technologies to create a low-carbon solution for heating and hot water needs. By switching between the gas combi boiler and the ASHP, the system maximizes efficiency and significantly reduces gas consumption by up to 82.5%.
If you already got lost in the abundance of energy-efficient boilers out there, then you'll need professional advice. Yet, finding reliable and qualified heating engineers nearby can be a challenge. But thankfully, our team at Boiler Guide can help you.
At Boiler Guide, we have a network of trusted Gas Safe registered engineers whose rates you can compare. Click the button below and we'll provide you with up to 3 free, no-obligation quotes from heating engineers in your area.
In the case of conventional boilers, together with the boiler itself, you'll also need tanks in the loft to store cold water and a cylinder. They're now pretty dated and are mostly found in older properties built in the 70s. Conventional boilers are still made though and are just as efficient as combi or system boilers.
However, you should only think about a new conventional boiler if your home already has one. Otherwise, go for a system boiler.
ATAG iR
Efficiency: 94%
Warranty: 12 years (with an option of 18 years)
Output sizes: 15kW-40kW
Price: £N/A
Key features: ATAG iCon stainless steel heat exchanger, underfloor heating systems compatibility, fully compatible with solar thermal hot water systems and ATAG iSteel twin coil cylinder range.
ATAG iR boilers are offered in a range of capacities spanning from 15kW to 40kW, catering effectively to various households regardless of their hot water requirements. Additionally, integrating an ATAG iR regular boiler with the company's iSteel series of hot water cylinders enhances efficiency levels.
Specifically tailored for open-vented systems, the iR regular boilers by ATAG present a wealth of possibilities for larger residences with elevated demands for hot water volume.
Ideal Logic Heat
Efficiency: 93%-94%
Warranty: 2-10 years
Output sizes: 12kW-30kW
Price: £712-939
Awards: ERP compliance badge, Quiet Mark certified
Key features: Compact cupboard fit, compatible with the Halo thermostat range, integrated connectivity for remote monitoring using Link Cellular.
This boiler is designed for the unpredictable UK climate and ensures hot water availability even in the harshest weather, safeguarding against freezing temperatures, rain, ice, and snow, and providing uninterrupted hot water when you need it most.
IDEAL Logic Heat proudly bears the ERP compliance badge and is Quiet Mark certified.
Ariston Clas One introduces the cutting-edge XtraTech Stainless Steel Heat Exchanger which adapts seamlessly to varying demands, ensuring optimal performance and energy utilisation at all times. It also features an optimised internal silencer, guaranteeing quiet operation while maintaining peak performance.
Such a technology boasts high efficiency not only at nominal outputs (97.5-97.9%) but also at varying conditions: at 30-50°C heating output (107.3-108.2%) and even at 30°C heating output (109.6-109.8%).
How much does an energy-efficient boiler save you?
Older boiler models are generally far less efficient than new condensing models. This is because new condensing boilers have larger heat exchangers, meaning they recover more heat that would have otherwise been lost through the flue.
If you install a new boiler, you'll reduce the amount of energy needed to heat your home. Since new boilers are generally highly efficient, they will help you save a few pennies on your energy bills.
For example, as of April 2024*, having a condensing A-rated boiler instead of a G-rated boiler can save you £522!
Savings with an energy-efficient boiler
Old boiler rating
Detached
Semi-detached
Bungalow
Mid-terrace house
Flat
D (78-82%)
£239
£194
£176
£162
£72
E (74-78%)
£288
£216
£194
£180
£81
F (70-74%)
£369
£243
£216
£203
£90
G (<70%)
£522
£347
£311
£288
£131
*Figures based on fuel prices as of April 2024 for installing a new A-rated condensing boiler with a programmer, room thermostat, and thermostatic radiator controls (TRVs) in a gas-heated home from an older boiler with a programmer and room thermostat.
Sounds like what you're looking for? Then you'll need to consult a certified heating engineer. However, finding a professional you can trust is a real challenge for a busy homeowner. Sacrificing time out with friends to search, call, and vet experts is unlikely what you're up for at the weekend.
Luckily, Boiler Guide can help you out! Completing our form takes less than a minute and brings you up to 3 free quotes from heating experts. You can compare those quotes to find the best deal. Our offer is completely free and non-binding. Just click the button below to get started!
What is the most efficient gas boiler in 2024?
There's no one exact most efficient gas boiler in 2024 in the UK. Some of the best energy-efficient boilers are produced by Worcester Bosch, Viessmann, and Vaillant.
What are the benefits of an energy-efficient boiler?
Energy-efficient boilers are an environmentally friendly option as they produce less emissions and thus contribute to a cleaner environment. In addition, they can use less fuel for heating which results in lower energy bills.
Are there energy-efficient boiler grants?
Yes, there are several government-backed incentives that provide funding for energy-efficient boilers. Contact a Gas Safe engineer to find out whether you qualify for a grant.
Which boiler is the most efficient?
There are several highly efficient gas boilers available in the UK, with different models and brands offering different levels of efficiency. Generally speaking, Ideal, Viessmann and Worcester Bosch offer the most efficient boilers in the UK.
How efficient is a 10-year-old boiler?
A 10-year-old boiler is usually 80-85% efficient. Upgrading to a new, energy-efficient boiler can lead to savings on energy bills of up to £522 and reduce your carbon emissions.
Output range: 25.4-32kW
Output range: 12-24kW
Output range: 26-40kW
Efficiency: 94%
