What Is The Most Efficient Boiler In The UK?

The Most Efficient Boiler In The UK

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Ever wonder how you can keep your home warm without sending your energy bills skyrocketing? The answer might lie in your boiler. Modern, energy-efficient condensing boilers boast a range of benefits that can transform your home heating experience. Undeniably, they catch heat that would normally escape and use it again to warm your house. Basically, they waste less energy and put more money in your piggy bank. Moreover, they’re even small, so they won’t take up your tons of space.

Let’s explore what are the most energy-efficient boilers in the UK and how these innovative systems can save you money. We’ll also discuss how you can get an energy-efficient boiler free of cost through a free boiler grant.

What’s Boiler Efficiency?

Boiler efficiency refers to how well a boiler converts fuel into usable heat for your home. Imagine you buy £100 worth of fuel for your boiler. Ideally, all that fuel should be used to heat your home. But in reality, some heat escapes as waste. So boiler efficiency is a percentage that tells you how much of the fuel is actually used for heating. Moreover, a highly efficient boiler, like a condensing boiler, might have an efficiency of 95%. This means it uses 95% of the fuel to heat your home, and only wastes 5%.

On the other hand, an older, less efficient boiler might only have an efficiency of 60%. That means a whopping 40% of the fuel you pay for goes to waste. So, the higher the boiler efficiency, the less fuel you waste and the lower your energy bills will be.

What is an energy-efficient boiler?

An energy-efficient boiler effectively converts fuel (such as natural gas, oil, or coal) into useful heat. It calculates the useful heat output by dividing it by the total energy input. Furthermore, boiler efficiency is typically expressed as a percentage, ranging from 50% to 98%. Also, there are some factors that affect efficiency including the type of fuel, boiler design, and proper operation

Why do we call it energy efficient? We label a boiler as energy-efficient because it maximises useful heat output while minimising energy losses. For instance, a 90% efficient boiler loses only 10% of the energy input. But efficient boilers save money by reducing fuel costs. Furthermore, they contribute to environmental sustainability by minimising carbon emissions. So choosing an efficient boiler matters for cost savings and environmental impact.

What factors affect boiler efficiency?

Several factors can impact boiler efficiency. So you should have an idea of these factors before and after installation of a boiler. Here are some key ones:

  • Combustion efficiency: Firstly, efficient combustion of fuel is crucial. So, a proper air-to-fuel ratio ensures complete combustion. It minimises waste.
  • Heat losses: This is also a critical factor. Heat can be lost through the flue gas stack. 
  • Radiation and convection loss: Here heat is lost from the boiler surface.
  • Boiler design and sizing: Next, well-designed boilers optimise heat transfer and minimise losses. Furthermore, proper sizing ensures efficient operation.
  • Boiler load: Next, efficiency varies with load. However, operating near the design load improves efficiency.
  • Fuel type and quality: No doubt, different fuels have varying calorific values, but high-quality fuel boosts efficiency.
  • Water treatment: Proper water treatment prevents scale and corrosion. It also maintains heat transfer efficiency.
  • Maintenance and tuning: Now, if you regularly opt for maintenance, for sure, it will increase optimal boiler performance. On top of that, tuning adjusts combustion parameters for efficiency.

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What’s an ErP system and how does it work?

The “Energy-related Products” or ErP Label is like a sticker on appliances such as boilers. It shows how efficient they are. The European Union (EU) rolled out this rule in 2015 to ramp up the efficiency of heating products. Now, the label ranges from A++ (super efficient) to G (not so great). Boilers with an A++ rating are energy and money savers. Total Energy Services, for instance, installs A-rated boilers that are over 90% energy efficient. Moreover, modern boilers recover more heat, keeping you warm without wasting energy. So, if you’re looking to cut down on energy costs, consider getting an A-rated boiler.

On top of that, the EU continues to push for more energy-efficient products. This move not only helps consumers save money but also contributes to environmental sustainability.

How can I check if my current boiler has an ErP label?

Well, this is easy peasy. You can find your boiler’s ErP label, by looking at a sticker on your boiler. It shows an energy rating from A++ to G. Can’t find it? Don’t give up. Well, check the manufacturer’s website or product manual. Some, like Worcester Bosch, even offer online tools. These tools calculate and generate the ErP system label for you.

Remember, the ErP label tells you about your boiler’s energy efficiency. It also helps you understand its impact on your energy bills.

What are the most energy-efficient boiler models of Alpha?

Alpha boilers strive to put efficiency at the heart of what they do. Many of their boilers come with an ErP ‘A’ rating, which indicates high energy efficiency. Now, let’s take a look at some of their boiler models:

  • E-Tec: Alpha’s E-Tec range is their smallest Combi boiler ever. Despite its compact size, it can deliver 14.1 liters of water per minute. So this is suitable for small to medium-sized homes.
  • Evoke: The Evoke range, exclusively available from independent merchants. It features a brand-new stainless steel heat exchanger. Moreover, these boilers are compact and easy to service.
  • InTec: Alpha’s InTec Combi boilers provide central heating and hot water on-demand. The InTec GS model is fitted with Gas Saver technology. It can also reduce gas usage for hot water by 35%.
  • ProTec Plus: Designed for homes with higher heating demands, the ProTec Plus system boilers offer enhanced circulation and efficiency.


In terms of energy efficiency, the Alpha E-Tec boasts an impressive percentage of 93%. But keep in mind that the most efficient boilers fired by natural gas or propane can reach up to 97% AFUE (Annual Fuel Utilization Efficiency). So, while Alpha’s boilers are efficient, there are even more efficient options out there. If you’re specifically interested in Alpha, the E-Tec is a solid choice!

What are the most efficient Worcester Bosch boiler models?

  • Greenstar 8000 Style Combi: This stunning design-led combi boiler is available in high gloss black or white. Moreover, it’s part of Worcester Bosch’s most powerful wall-hung boiler range, effortlessly heating larger homes. Plus, it’s their most connected and intelligent boiler, with wireless connectivity to the Bosch EasyControl.
  • Life Combi Greenstar 8000: Featuring a modern new design, this combi boiler is also part of the powerful wall-hung range. It’s suitable for larger homes. It also offers wireless compatibility with the Bosch EasyControl.
  • Heatslave II External Greenstar: If you’re looking for an oil external boiler, this is the UK’s most popular choice.It works well for small, medium, and large-sized homes, filling a kitchen sink in just 22 seconds.
  • Greenstar Heatslave II: Another popular oil combi boiler, suitable for various home sizes. It also fills a kitchen sink in 22 seconds.

What are the leading energy-efficient boiler models from Viessmann?

  • Vistodens 200-W: This model boasts an impressive 98% efficiency. As a result, it can save you big on fuel bills.
  • Vitodens 100-W: This reliable option offers models with efficiencies reaching 97%. So it can keep your wallet happy.

Both these Viessmann boilers are condensing models, the top performers in energy savings.

Which Vaillant boilers have the highest energy efficiency?

Vaillant boasts some champions when it comes to energy-efficient boilers! Here’s a quick look at their top contenders:

  • Vaillant ecoTEC exclusive with Green iQ: This powerhouse boasts an impressive 94% efficiency. As a result, it wastes less energy and lowers your fuel bills.
  • Vaillant ecoTEC Plus range: This entire range shines with high efficiency, some models reaching up to 90.7%. They’re perfect for keeping your home warm without burning a hole in your pocket.

What are the best energy-efficient boilers offered by Ideal?

Ideal also isn’t shy about energy-saving boilers! Here are their top picks for keeping your wallet warm:

  • Ideal Logic + Combi: This champion boasts a stellar 94% efficiency, squeezing the most warmth from every drop of fuel.
  • Ideal Vogue Max Combi: This sleek option offers high efficiency, reaching up to 92%, keeping you warm without breaking the bank.


Both these Ideal boilers are condensing models. They capture extra heat that would normally escape, making them energy-saving superstars!

Need a new boiler?

Upgrade to an A-rated boiler at no cost with the Berks insulation.
As a UK landlord, enhance your property’s value and save on energy costs.

Check your Eligibility Now

Can you name the most energy-efficient boiler models by Baxi?

Baxi brings the heat while saving you money! Here are their top contenders for energy-efficient boilers:

  • Baxi 600 Combi: This champion boasts a fantastic 93% efficiency, saving you big on fuel costs.
  • Baxi EcoBlue Combi range: This entire range shines with high efficiency, with all models reaching at least 92% ErP rating.

Overview of best boiler models in the UK

Upgrading your boiler to a more efficient model can be a smart investment. But with so many brands and models on the market, how do you pick the right one? Here’s a breakdown of some of the leading boiler brands in the UK, highlighting their most energy-efficient models, ErP rating, warranty, and estimated price range (prices may vary depending on retailer and installation). This comparison table can help you choose the boiler that keeps your home warm and your wallet happy.


Most Efficient Model

ErP Efficiency Rating

Warranty (Years)

Estimated Price Range


Ideal Logic + Combi


7 (optional)

£1,200 – £1,800

Worcester Bosch

Worcester Bosch Greenstar 8000 Life



£1,300 – £2,000


Baxi 600 Combi


7 (optional)

£900 – £1,500


Vaillant ecoTEC exclusive with Green iQ


5 (optional)

£1,400 – £2,200


Alpha Ecombi boiler (varies by model)

Up to 93%

7 (optional)

£800 – £1,400


Viessmann Vitodens 200-W


10 (optional)

£1,700 – £2,500

While ErP rating is a good indicator of efficiency, it’s not the only factor to consider. Consulting a qualified heating engineer can help you choose the right boiler for your specific needs and budget.

How a new boiler can save you money?

Upgrading to an energy-efficient condensing boiler can save you big bucks! New condensing boilers are much smarter. They squeeze more heat out of every drop of fuel, reaching efficiencies of up to 94%. This means for every £100 you spend, you only lose £6-£8 on wasted energy. That translates to real savings – up to £500 a year on your energy bills! Now that’s money you can put towards something fun!

How can I improve my boiler's efficiency?

Improving your boiler’s efficiency involves several steps:

  • Regular maintenance: Schedule professional inspections to ensure optimal performance. Clean or replace filters, check for leaks, and maintain proper water chemistry.
  • Tune the combustion process: Firstly, adjust air-to-fuel ratio for complete combustion. Secondly, optimise burner settings to minimise excess air.
  • Insulate pipes and surfaces: You should insulate exposed pipes to avoid heat loss. Moreover, insulating the boiler itself will reduce radiation and convection losses.
  • Upgrade controls and sensors: Next, install modern controls (e.g., programmable thermostats) for better efficiency. Moreover, you can use outdoor temperature sensors to adjust boiler operation.
  • Consider condensing boilers: Condensing boilers recover heat from flue gases. Moreover, they are more efficient than traditional boilers.
  • Use high-quality fuel: Choose clean, high-calorific-value fuel. Furthermore, regularly service burners to maintain efficiency.

Are there any grants to get energy-efficient boilers free of cost?

Well, the ECO4 scheme is a UK government program that offers free boiler replacements to eligible households. This project aims to improve energy efficiency and reduce fuel poverty. So if you’re concerned about the high cost of heating your home with an old boiler, the ECO4 scheme might be worth exploring. However, eligibility is restricted to certain groups, such as those on specific benefits or with a low income.

Now, if you want to know if you qualify, enter your postcode and we’ll let you know about your eligibility in less than 60 seconds.

Need a new boiler?

Upgrade to an A-rated boiler at no cost with the Berks insulation.
As a UK landlord, enhance your property’s value and save on energy costs.

Check your Eligibility Now

Bottom line

While there’s no single “most efficient boiler” in the UK, several brands offer top-tier options boasting impressive ErP ratings. However, the ideal choice for you depends on factors like your budget, home size, and heating needs. Considering the data, Viessmann stands out with the Vitodens 200-W reaching a remarkable 98% efficiency. 

As a result, this offers significant savings on fuel bills. But, Viessmann boilers tend to be on the pricier end. For a balance of efficiency and affordability, Ideal and Worcester Bosch offer compelling options like the Ideal Logic + Combi (94% ErP) and Worcester Bosch Greenstar 8000 Life (94% ErP). These models provide excellent value while delivering substantial energy savings.

Baxi and Vaillant are also strong contenders. Baxi’s 600 Combi boasts a fantastic 93% ErP rating, while Vaillant’s ecoTEC exclusive with Green iQ reaches an impressive 94% ErP. Truly both brands offer a good mix of efficiency and price competitiveness. Next, remember that condensing boilers are the undisputed champions of energy efficiency. They capture heat that would normally escape. 

So they maximise fuel usage and minimise waste. Secondly, when considering a new boiler, prioritise condensing models for the best long-term savings. Moreover, beyond the boiler itself, consider additional factors that can further enhance your home’s energy efficiency. So proper insulation, efficient thermostats, and regular boiler servicing can all contribute to lower energy bills. Ultimately, the best boiler for you strikes a balance between efficiency, budget, and your specific needs.

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