What Type of Boiler is the Most Energy Efficient?

Choosing the right boiler for your home can significantly impact your energy bills and environmental footprint.

For homeowners exploring heating solutions, identifying the most energy-efficient boiler is key to maximising cost savings and minimising emissions.

In this article, you will learn:

  • How different types of boilers compare in energy efficiency.
  • The impact of installation and maintenance on boiler efficiency.
  • Which boilers offer the best long-term savings.

Understanding the nuances of boiler efficiency will help you make an informed decision that aligns with both your heating needs and environmental goals.

What type of boiler is most energy efficient?

Types of Boilers

When selecting a boiler, understanding the different types available is crucial.

In the UK, there are mainly three types of boilers that homeowners choose from: combi, system, and conventional boilers. Each type has unique characteristics that can affect your home’s heating efficiency and comfort.

Combi Boilers

  • Functionality: Combination boilers, commonly known as combi boilers, provide both heating and hot water directly from the boiler. They do not require a separate hot water storage cylinder or cold water tank, making them compact and ideal for smaller homes.
  • Energy Efficiency: Combi boilers are known for their high efficiency, as they heat water directly from the mains when you turn on a tap, ensuring minimal heat loss. This can significantly reduce energy consumption and lower bills.

System Boilers

  • Functionality: System boilers require a hot water storage cylinder but no cold water tank. They are suitable for homes with more than one bathroom, as they can provide a constant supply of hot water to multiple taps at once. You can also check out our Ultimate Guide To System Boilers article for further information.
  • Energy Efficiency: While system boilers are less efficient than combi boilers due to the need to heat a cylinder of water, they are more efficient than conventional boilers and are a good middle-ground for larger households.

Conventional Boilers

  • Functionality: Also known as regular boilers or open vent boilers, conventional boilers require both a hot water cylinder and a cold water tank. They are typically suited for homes that already have an older radiator system which might not be able to cope with the high water pressure from combi or system boilers.
  • Energy Efficiency: Conventional boilers are the least energy-efficient option as they heat and store water in a cylinder, which can lead to heat loss. However, they can be a suitable choice for homes with higher water use or low water pressure.

Each boiler type has its advantages and disadvantages depending on your home’s size, water usage, and existing heating system. Understanding these can help you choose the boiler that best fits your energy efficiency goals.

Factors Influencing Energy Efficiency

The energy efficiency of a boiler is not solely determined by the type of boiler you choose.

Several other factors play critical roles in how efficiently your boiler operates, which, in turn, affects your energy consumption and cost.

Size of the Boiler

Selecting the right size boiler for your home is essential. An oversized boiler will use more energy than necessary, leading to wasted energy, whereas an undersized boiler will struggle to heat your home effectively, potentially increasing wear and tear and reducing efficiency over time.


Proper boiler installation is critical to a boiler’s efficiency. Incorrect installation can lead to heat loss, increased energy consumption, and frequent repairs. It’s vital to hire a qualified professional who understands the specific requirements of your chosen boiler type and your home’s heating system.


Regular boiler maintenance is necessary to keep your boiler running efficiently. This includes annual check-ups, cleaning of key components, and prompt repairs. A well-maintained boiler not only performs better but also lasts longer, saving you money in the long run.

Thermostat and Controls

Advanced thermostats and controls can significantly enhance boiler efficiency. Smart thermostats allow for better temperature management throughout your home, avoiding over-heating and minimising energy wastage. Programmable options ensure that energy is used only when needed, adapting to your lifestyle and schedule.


The overall insulation of your home also affects boiler efficiency. Better insulated homes retain heat more effectively, reducing the workload on your boiler and thereby increasing its efficiency. Investing in good quality insulation, sealed windows, and draft-proofing can drastically reduce heat loss.

By considering these factors, you can optimise the efficiency of your boiler and significantly reduce your energy bills. Ensuring your boiler is appropriately sized, correctly installed, and regularly maintained, along with effective use of controls and home insulation, will help you achieve the best performance from your heating system.

Most Energy Efficient Boiler Comparison

Comparing Energy Efficiency of Different Boiler Types

To make an informed decision on which boiler to choose, it’s essential to compare the energy efficiency of combi, system, and conventional boilers. Each type has specific advantages that can suit different household needs, but understanding their efficiency levels will help you optimize energy use and cost.

Combi Boilers & Energy Efficiency

  • Efficiency: Combi boilers are highly efficient as they heat water directly from the mains only when it’s needed, reducing heat loss significantly. Most new combi boilers have an efficiency rating of over 90%, making them an excellent choice for smaller households looking to minimise energy wastage.
  • Suitability: Best for smaller homes with limited space and lower hot water demand.

System Boilers & Energy Efficiency

  • Efficiency: While system boilers need to heat a cylinder of water, they are still quite efficient. Modern system boilers also tend to have high energy efficiency ratings, close to those of combi boilers, especially when equipped with modern controls and a well-insulated cylinder.
  • Suitability: Ideal for homes with multiple bathrooms and higher hot water demand.

Conventional Boilers & Energy Efficiency

  • Efficiency: The least efficient of the three, conventional boilers require heating water stored in a cylinder, which can lead to significant heat loss. However, they can still be a suitable option if upgraded with modern controls and insulation to improve efficiency.
  • Suitability: Suitable for larger homes with high water usage and lower water pressure systems.

Energy Star Ratings

Additionally, looking at the Energy Star ratings can provide further guidance on energy efficiency. These ratings help consumers compare and contrast different models based on their energy performance.


Although more efficient boilers may be more expensive initially, their ability to lower energy bills over time can make them more cost-effective in the long run. Considering the lifespan of the boiler, energy-efficient models could offer significant savings.

Choosing the right type of boiler involves balancing upfront costs against long-term savings and considering the specific needs of your household – remember boiler finance can also be an option.

By comparing the different types, you can select the most efficient boiler that meets your requirements and contributes to substantial energy savings.

Energy Efficient Boiler Cost Comparison

Cost Considerations

Choosing the most energy-efficient boiler is not only about reducing energy consumption but also about understanding the financial implications. The costs associated with different types of boilers can vary widely, not just in terms of initial purchase but also in long-term energy savings and maintenance.

Initial Cost

  • Combi Boilers: These are generally less expensive to install than other types because they do not require a hot water storage tank or additional pipework. However, the cost can vary depending on the brand and capacity.
  • System Boilers: System boilers are usually more expensive than combi boilers because they require additional components like a hot water cylinder. The overall installation cost also includes the price of the cylinder and extra pipework.
  • Conventional Boilers: Typically, conventional boilers are the most expensive to install due to their complexity and the need for both a hot water cylinder and a cold water tank.

Running Costs

  • Energy Efficiency: More energy-efficient boilers, like modern combi and system boilers, tend to have lower running costs because they waste less energy. The higher initial investment often pays off through reduced energy bills over time.
  • Fuel Type: The type of fuel the boiler uses also affects running costs. Gas boilers are usually cheaper to run than electric or oil boilers, though prices can fluctuate based on fuel market prices.

Maintenance and Repair Costs

  • Longevity: Regular maintenance can extend the life of any boiler type, but the complexity of the system might affect how often repairs are needed and how costly they can be.
  • Spare Parts: Conventional and system boilers might have more parts available in the market, potentially reducing repair costs compared to the more specialized parts needed for some high-efficiency combi boilers.

Long-Term Savings

Considering the boiler’s lifespan, which can be up to 15 years or more, the long-term energy savings should be factored into the cost. Energy-efficient boilers, while more costly upfront, can offer substantial savings on energy bills, making them a wise investment over time.

Understanding these cost factors can help you make an informed decision about which boiler type will be the most economical in the long run, taking into account both upfront expenses and potential energy savings.

How to choose the right boiler

How to Choose the Right Boiler for Your Needs

Selecting the right boiler involves more than just comparing types and costs. It requires a detailed assessment of your home’s heating needs, your lifestyle, and the long-term value of the investment.

Here are some key considerations to guide you in choosing the most energy-efficient boiler for your home:

Assess Your Home’s Heating Demand

  • Determine the size of your home and the number of bathrooms. Larger homes with multiple bathrooms might benefit from a system or conventional boiler, while smaller homes with less demand for hot water are often better suited to combi boilers.
  • Consider the water pressure available in your area. Homes with low water pressure might not perform well with combi boilers, which rely on strong mains pressure.

Energy Efficiency Goals

  • Prioritise boilers with high energy efficiency ratings. Look for the latest models that comply with current energy standards and have high Energy Star ratings.
  • Evaluate the potential energy savings over the boiler’s lifetime, taking into account the typical energy prices in your area.

Installation and Maintenance

  • Choose a reputable installer who is experienced with your chosen type of boiler. Proper installation is crucial for optimal boiler performance and efficiency.
  • Plan for regular maintenance and consider the availability and cost of spare parts for the boiler model you choose. Regular servicing not only prolongs the life of the boiler but also ensures it runs efficiently.

Budget and Long-Term Costs

  • Balance the upfront cost of the boiler with long-term savings. More expensive boilers may offer greater efficiency and lower ongoing energy costs, providing better value over time.
  • Consider available grants and incentives. In some regions, there may be financial assistance available for installing energy-efficient heating systems.

By thoroughly assessing these factors, you can choose a boiler that not only meets your immediate heating needs but also aligns with your long-term energy and financial goals, ensuring you invest wisely in your home’s comfort and efficiency.

The Key Takeaways

  • Type Comparison: Combi boilers are best for smaller homes with less demand for hot water, while system and conventional boilers suit larger homes with higher water demands.
  • Efficiency Factors: Installation quality, regular maintenance, and proper sizing are critical for maximizing boiler efficiency.
  • Cost Effectiveness: While initial costs can vary, the long-term savings from choosing a more efficient boiler can significantly outweigh these initial investments.

As you consider upgrading or installing a new boiler, consulting with a professional to assess your specific needs can provide further personalized guidance. For those interested in deepening their understanding of home energy efficiency, exploring topics like sustainable home heating solutions could be a beneficial next step.

Frequently Asked Questions

What is the most energy-efficient type of boiler?

Combi boilers are generally considered the most energy-efficient type of boiler as they heat water directly from the mains only when it’s needed, reducing heat loss and energy wastage.

How often should I service my boiler to maintain its efficiency?

It is recommended to service your boiler annually to ensure it operates at peak efficiency. Regular maintenance can help prevent unexpected breakdowns and extend the life of your boiler.

Can upgrading my boiler really help reduce my energy bills?

Yes, upgrading to a more energy-efficient boiler can significantly reduce your energy bills. Modern boilers are designed to use less energy to produce the same amount of heat as older models, which can lead to substantial savings.

What should I consider when choosing a boiler for a large home?

For larger homes, particularly those with multiple bathrooms, system boilers or conventional boilers are often more suitable. They can handle higher demand for hot water and are more efficient in homes where multiple outlets are used simultaneously.

Are there any government incentives for installing energy-efficient boilers?

In many regions, there are government incentives or rebates available for installing energy-efficient appliances, including boilers. It’s advisable to check local government or energy supplier websites for up-to-date information on available incentives.

If you’d like to talk to us about your own boiler, please don’t hesitate to ger in touch by calling Max on 07545 198220 or heading over to our contact page.

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