Boiler Efficiency Ratings: How to Choose the Best Boiler for Your Home

When it comes time to replace your boiler, you have a lot of choices to make. One of the most important decisions is which boiler is right for your home. There are a variety of factors to consider when making this decision, but one of the most important is the boiler’s energy efficiency rating. In this blog post, we will discuss boiler efficiency ratings and how to choose the best boiler for your needs.

What Are Boiler Efficiency Ratings?

A boiler efficiency rating is an indicator of how efficient a boiler is. The rating is expressed as a percentage and is determined by how much heat the boiler produces compared to the amount of fuel it consumes. The higher the rating, the more efficient the boiler.

The energy efficiency score is calculated by dividing the boiler’s net heat output by the amount of fuel it consumes. So, a boiler with an efficiency rating of 90% would produce 90% of the energy it consumes in heat.

In the UK, domestic boilers are rated A-G, with A being the most efficient and G the least.

Why Is Boiler Energy Efficiency Important?

Boiler efficiency is important because it affects how much you’ll pay for heating your home. The higher the energy rating, the lower your energy bills will be. With the latest energy crisis, it has become even more vital to choose an energy-efficient boiler.

Modern boilers are usually much more efficient than older ones, and the savings you’ll make over time can be considerable.

The Most Energy Efficient Boiler Types To Consider

The most energy efficient boilers are:

System Boilers

A system boiler is a type of boiler that is designed to provide hot water on demand from a storage cylinder. This makes system boilers a good choice for larger families with high hot water demands. System boilers are also very energy efficient, with an efficiency rating of 97%. This means that they can help to save you money on your heating bills. If you are considering installing a new boiler, then a system boiler may be the right option for you.


Electric boilers are a popular choice for homeowners looking for an efficient and environmentally-friendly heating solution. Electric boilers have many advantages over traditional gas or oil-fired boilers, including a lower carbon footprint and higher efficiency. Electric boilers are also a good choice if you are already using electricity for heating. These boilers have an efficiency rating of 99%, which is one of the most efficient on the market today. In addition, electric boilers are very quiet and require no venting, making them a great option for homes with limited space.

Biomass Boilers

Biomass boilers are a type of renewable energy technology that uses organic matter to generate heat. Wood, crop waste, and other organic materials can all be used as fuel for a biomass boiler.

When burned, these materials release heat energy that can be used to power central heating systems and provide hot water. These are typically more expensive than gas or oil boilers, but they offer a number of advantages. For one, some models boast efficiency ratings of up to 93%.

This means that less fuel is required to generate the same amount of heat, making them cost-effective in the long run. In addition, biomass boilers emit far fewer greenhouse gases than fossil fuel-based systems, making them an environmentally friendly choice.

Lastly, they are ideal for people who live in rural areas with access to wood and other organic materials. If you are considering installing a biomass boiler in your home, be sure to do your research and choose a reputable brand.

Combi Boilers

Combi boilers are the most common type of domestic boiler in the UK, and they are also very energy efficient. With an efficiency rating of 98%, they are able to heat water on demand, meaning that you don’t have to wait for hot water to come through the taps.

This makes them ideal for busy households where there is a lot of demand for hot water. Combi boilers are also very compact, which makes them perfect for small homes or apartments.

Condensing Boilers

Condensing boilers are designed to be more efficient than traditional boilers, and as a result, they can help to reduce your energy bills. All condensing boilers must have an efficiency rating of at least 90%, which means that they use less fuel to generate the same amount of heat.

In addition, condensing boilers recover heat from the flue gases that would otherwise be lost up the chimney. This recovered heat is used to pre-heat the cold water that enters the boiler, resulting in even further savings.

Oil & Gas

Oil and gas boilers both have their advantages and disadvantages when it comes to energy efficiency. Oil boilers are the most expensive to purchase, but they offer greater efficiency than electric models (energy rating of 95%).

Gas boilers are the least expensive to purchase but have a rating of 91% which is lower than oil or electric models.

If you’re looking for the most efficient option, oil is the way to go. However, if you’re looking for a more economical option, gas may be a better choice. Ultimately, the decision comes down to personal preference and budget.


LPG boilers are a good option for homeowners who want the convenience of gas but live in an area where there is no access to mains gas (efficiency rating of 93%).

In Conclusion

To find the boiler that is right for your home, it’s important to know what you are looking for. That means understanding how efficiency ratings work and why they matter so much when choosing a new boiler. If you have any questions regarding the many sorts of boilers or want to book a service appointment for any boiler repairs or maintenance required on your present system, call us immediately!